Update Variable.swift - Fixed a typo for objc runtime check

Release 0.15.1

.github/dependabot.yml

@@ -0,0 +1,7 @@
+version: 2
+updates:
+  # Maintain dependencies for GitHub Actions
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"

.github/workflows/danger.yml

@@ -0,0 +1,25 @@
+name: Danger
+
+on:
+  push:
+    branches: master
+  pull_request:
+
+jobs:
+  check:
+    name: Danger Check
+    runs-on: ubuntu-latest
+    steps:
+      - 
+        name: Checkout
+        uses: actions/checkout@v3
+      - 
+        name: Setup Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+      -
+        name: Run Danger
+        run: bundle exec danger --verbose --dangerfile=rakelib/Dangerfile
+        env:
+          DANGER_GITHUB_API_TOKEN: ${{ secrets.danger_github_api_token }}

.github/workflows/lint-cocoapods.yml

@@ -0,0 +1,23 @@
+name: Lint Cocoapods
+
+on:
+  push:
+    branches: master
+  pull_request:
+
+jobs:
+  lint:
+    name: Pod Lint
+    runs-on: ubuntu-latest
+    steps:
+      - 
+        name: Checkout
+        uses: actions/checkout@v3
+      - 
+        name: Setup Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+      -
+        name: Lint podspec
+        run: bundle exec rake pod:lint

.github/workflows/release-check-versions.yml

@@ -0,0 +1,23 @@
+name: Check Versions
+
+on:
+  push:
+    branches: 
+      - 'release/**'
+
+jobs:
+  check_versions:
+    name: Check Versions
+    runs-on: ubuntu-latest
+    steps:
+      - 
+        name: Checkout
+        uses: actions/checkout@v3
+      - 
+        name: Setup Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+      -
+        name: Check versions
+        run: bundle exec rake release:check_versions

.github/workflows/swiftlint.yml

@@ -0,0 +1,26 @@
+name: SwiftLint
+
+on:
+  push:
+    branches: master
+  pull_request:
+
+jobs:
+  lint:
+    name: SwiftLint
+    runs-on: macos-latest
+    steps:
+      - 
+        name: Checkout
+        uses: actions/checkout@v3
+      - 
+        name: Setup Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+      -
+        name: Lint source code
+        run: bundle exec rake lint:code
+      -
+        name: Lint tests source code
+        run: bundle exec rake lint:tests

.github/workflows/tag-publish.yml

@@ -0,0 +1,44 @@
+name: Publish on Tag
+
+on:
+  push:
+    tags:
+      - '*'
+  workflow_dispatch:
+
+jobs:
+  cocoapods:
+    name: Push To CocoaPods
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v3
+      -
+        name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+      -
+        name: Push to CocoaPods
+        run: bundle exec rake release:cocoapods
+        env:
+          COCOAPODS_TRUNK_TOKEN: ${{secrets.COCOAPODS_TRUNK_TOKEN}}
+
+  github:
+    name: GitHub Release
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v3
+      -
+        name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+      -
+        name: Create release on GitHub
+        run: bundle exec rake release:github
+        env:
+          DANGER_GITHUB_API_TOKEN: ${{ secrets.danger_github_api_token }}

.github/workflows/test-spm.yml

@@ -0,0 +1,66 @@
+name: Test SPM
+
+on:
+  push:
+    branches: master
+  pull_request:
+
+jobs:
+  linux:
+    name: Test SPM Linux
+    runs-on: ubuntu-latest
+    container: swiftgen/swift:5.6
+    steps:
+      - 
+        name: Checkout
+        uses: actions/checkout@v3
+      - 
+        # Note: we can't use `ruby/setup-ruby` on custom docker images, so we
+        # have to do our own caching
+        name: Cache gems
+        uses: actions/cache@v3
+        with:
+          path: vendor/bundle
+          key: ${{ runner.os }}-gems-${{ hashFiles('Gemfile.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-gems-
+      - 
+        name: Cache SPM
+        uses: actions/cache@v3
+        with:
+          path: .build
+          key: ${{ runner.os }}-spm-${{ hashFiles('Package.resolved') }}
+          restore-keys: |
+            ${{ runner.os }}-spm-
+      -
+        name: Bundle install
+        run: |
+          bundle config path vendor/bundle
+          bundle install --jobs 4 --retry 3
+      -
+        name: Run tests
+        run: bundle exec rake spm:test
+
+  macos:
+    name: Test SPM macOS
+    runs-on: macos-latest
+    steps:
+      - 
+        name: Checkout
+        uses: actions/checkout@v3
+      - 
+        name: Setup Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+      - 
+        name: Cache SPM
+        uses: actions/cache@v3
+        with:
+          path: .build
+          key: ${{ runner.os }}-spm-${{ hashFiles('Package.resolved') }}
+          restore-keys: |
+            ${{ runner.os }}-spm-
+      -
+        name: Run tests
+        run: bundle exec rake spm:test

.gitignore

@@ -1,5 +1,75 @@
-.conche/
+# Xcode
-.build/
+#
+# gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore
+
+## Build generated
+build/
+DerivedData/
+Fixtures/stub-env/**/*.swiftmodule
+
+## Various settings
+*.pbxuser
+!default.pbxuser
+*.mode1v3
+!default.mode1v3
+*.mode2v3
+!default.mode2v3
+*.perspectivev3
+!default.perspectivev3
+xcuserdata/
+
+## Other
+*.moved-aside
+*.xcuserstate
+*.xcscmblueprint
+
+## Obj-C/Swift specific
+*.hmap
+*.ipa
+*.dSYM.zip
+*.dSYM
+
+## Playgrounds
+timeline.xctimeline
+playground.xcworkspace
+
+# Swift Package Manager
+#
+# Add this line if you want to avoid checking in source code from Swift Package Manager dependencies.
 Packages/
-Package.resolved
+.build/
-Package.pins
+.swiftpm/
+
+# CocoaPods
+#
+# We recommend against adding the Pods directory to your .gitignore. However
+# you should judge for yourself, the pros and cons are mentioned at:
+# https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control
+#
+# Pods/
+
+# Carthage
+#
+# Add this line if you want to avoid checking in source code from Carthage dependencies.
+Carthage/Checkouts
+Carthage/Build
+
+# fastlane
+#
+# It is recommended to not store the screenshots in the git repo. Instead, use fastlane to re-generate the
+# screenshots whenever they are needed.
+# For more information about the recommended setup visit:
+# https://github.com/fastlane/fastlane/blob/master/fastlane/docs/Gitignore.md
+
+fastlane/report.xml
+fastlane/Preview.html
+fastlane/screenshots
+fastlane/test_output
+
+# Other stuff
+.apitoken
+.DS_Store
+.idea/
+bin/
+Frameworks/
+Rome/

.ruby-version

@@ -0,0 +1 @@
+3.0.4

.swiftlint.yml

@@ -0,0 +1,124 @@
+swiftlint_version: 0.48.0
+
+opt_in_rules:
+ - accessibility_label_for_image
+ - anonymous_argument_in_multiline_closure
+ - anyobject_protocol
+ - array_init
+ - attributes
+ - balanced_xctest_lifecycle
+ - closure_body_length
+ - closure_end_indentation
+ - closure_spacing
+ - collection_alignment
+ - comment_spacing
+ - conditional_returns_on_newline
+ - contains_over_filter_count
+ - contains_over_filter_is_empty
+ - contains_over_first_not_nil
+ - contains_over_range_nil_comparison
+ - convenience_type
+ - discarded_notification_center_observer
+ - discouraged_assert
+ - discouraged_none_name
+ - discouraged_optional_boolean
+ - discouraged_optional_collection
+ - empty_collection_literal
+ - empty_count
+ - empty_string
+ - empty_xctest_method
+ - enum_case_associated_values_count
+ - fallthrough
+ - fatal_error_message
+ - file_header
+ - first_where
+ - flatmap_over_map_reduce
+ - force_unwrapping
+ - ibinspectable_in_extension
+ - identical_operands
+ - implicit_return
+ - implicitly_unwrapped_optional
+ - inclusive_language
+ - indentation_width
+ - joined_default_parameter
+ - last_where
+ - legacy_multiple
+ - legacy_objc_type
+ - legacy_random
+ - literal_expression_end_indentation
+ - lower_acl_than_parent
+ - missing_docs
+ - modifier_order
+ - multiline_arguments
+ - multiline_arguments_brackets
+ - multiline_function_chains
+ - multiline_literal_brackets
+ - multiline_parameters
+ - multiline_parameters_brackets
+ - nslocalizedstring_key
+ - nslocalizedstring_require_bundle
+ - number_separator
+ - operator_usage_whitespace
+ - optional_enum_case_matching
+ - overridden_super_call
+ - override_in_extension
+ - prefer_self_in_static_references
+ - prefer_self_type_over_type_of_self
+ - prefer_zero_over_explicit_init
+ - prefixed_toplevel_constant
+ - private_action
+ - private_outlet
+ - private_subject
+ - prohibited_super_call
+ - raw_value_for_camel_cased_codable_enum
+ - reduce_into
+ - redundant_nil_coalescing
+ - redundant_type_annotation
+ - required_enum_case
+ - return_value_from_void_function
+ - single_test_class
+ - sorted_first_last
+ - sorted_imports
+ - static_operator
+ - strong_iboutlet
+ - switch_case_on_newline
+ - test_case_accessibility
+ - toggle_bool
+ - trailing_closure
+ - unavailable_function
+ - unneeded_parentheses_in_closure_argument
+ - unowned_variable_capture
+ - unused_closure_parameter
+ - vertical_parameter_alignment_on_call
+ - vertical_whitespace_closing_braces
+ - vertical_whitespace_opening_braces
+ - void_function_in_ternary
+ - weak_delegate
+ - xct_specific_matcher
+ - yoda_condition
+
+# Rules customization
+closure_body_length:
+  warning: 25
+
+conditional_returns_on_newline:
+  if_only: true
+
+file_header:
+  required_pattern: |
+                    \/\/
+                    \/\/ Stencil
+                    \/\/ Copyright © 2022 Stencil
+                    \/\/ MIT Licence
+                    \/\/
+
+indentation_width:
+  indentation_width: 2
+
+line_length:
+  warning: 120
+  error: 200
+
+nesting:
+  type_level:
+    warning: 2

.travis.yml

@@ -1,22 +0,0 @@
-matrix:
-  include:
-    - os: osx
-      osx_image: xcode8.3
-      env: SWIFT_VERSION=3.1.1
-    - os: osx
-      osx_image: xcode9
-      env: SWIFT_VERSION=4.0
-    - os: osx
-      osx_image: xcode9.1
-      env: SWIFT_VERSION=4.0
-    - os: linux
-      env: SWIFT_VERSION=3.1.1
-    - os: linux
-      env: SWIFT_VERSION=4.0
-language: generic
-sudo: required
-dist: trusty
-install:
-  - eval "$(curl -sL https://swiftenv.fuller.li/install.sh)"
-script:
-- swift test

CHANGELOG.md

@@ -1,4 +1,281 @@
-# Stencil Changelog
+## 0.15.1
+
+### Bug Fixes
+
+- Fix bug in `LazyValueWrapper`, causing it to never resolve.  
+  [David Jennes](https://github.com/djbe)
+  [#328](https://github.com/stencilproject/Stencil/pull/328)
+
+## 0.15.0
+
+### Breaking
+
+- Drop support for Swift < 5. For Swift 4.2 support, you should use Stencil 0.14.2.  
+  [David Jennes](https://github.com/djbe)
+  [#323](https://github.com/stencilproject/Stencil/pull/323)
+
+### Enhancements
+
+- Added support for trimming whitespace around blocks with Jinja2 whitespace control symbols. eg `{%- if value +%}`.  
+  [Miguel Bejar](https://github.com/bejar37)
+  [Yonas Kolb](https://github.com/yonaskolb)
+  [#92](https://github.com/stencilproject/Stencil/pull/92)
+  [#287](https://github.com/stencilproject/Stencil/pull/287)
+- Added support for adding default whitespace trimming behaviour to an environment.  
+  [Yonas Kolb](https://github.com/yonaskolb)
+  [#287](https://github.com/stencilproject/Stencil/pull/287)
+- Blocks now can be used repeatedly in the template. When block is rendered for the first time its content will be cached and it can be rendered again later using `{{ block.block_name }}`.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#158](https://github.com/stencilproject/Stencil/issues/158)
+  [#182](https://github.com/stencilproject/Stencil/pull/182)
+- Added `break` and `continue` tags to break or continue current loop.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#175](https://github.com/stencilproject/Stencil/pull/175)
+- You can now access outer loop's scope by labeling it: `{% outer: for ... %}... {% for ... %} {{ outer.counter }} {% endfor %}{% endfor %}`.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#175](https://github.com/stencilproject/Stencil/pull/175)
+- Boolean expressions can now be rendered, i.e `{{ name == "John" }}` will render `true` or `false` depending on the evaluation result.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [David Jennes](https://github.com/djbe)
+  [#164](https://github.com/stencilproject/Stencil/pull/164)
+  [#325](https://github.com/stencilproject/Stencil/pull/325)
+- Enable dynamic member lookup using a new `DynamicMemberLookup` marker protocol. Conform your own types to this protocol to support dynamic member from with contexts.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#219](https://github.com/stencilproject/Stencil/issues/219)
+  [#246](https://github.com/stencilproject/Stencil/pull/246)
+- Allow providing lazily evaluated context data, using the `LazyValueWrapper` structure.  
+  [David Jennes](https://github.com/djbe)
+  [#324](https://github.com/stencilproject/Stencil/pull/324)
+
+### Bug Fixes
+
+- Fixed using `{{ block.super }}` inside nodes other than `block`.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#266](https://github.com/stencilproject/Stencil/issues/266)
+  [#267](https://github.com/stencilproject/Stencil/pull/267)
+
+### Internal Changes
+
+- Updated internal maintenance scripts, and switched to GitHub actions.  
+  [David Jennes](https://github.com/djbe)
+  [#321](https://github.com/stencilproject/Stencil/pull/321)
+- Made the `tokens` property on a `Template` public.  
+  [Stefanomondino](https://github.com/stefanomondino)
+  [#292](https://github.com/stencilproject/Stencil/pull/292)
+- Made the `Template.render(_:)` method (that accepts a `Context`) public.  
+  [David Jennes](https://github.com/djbe)
+  [#322](https://github.com/stencilproject/Stencil/pull/322)
+
+## 0.14.2
+
+### Internal Changes
+
+- Update Spectre (0.10) and PathKit to support Xcode 13.  
+  [Astromonkee](https://github.com/astromonkee)
+  [#314](https://github.com/stencilproject/Stencil/pull/314)
+
+## 0.14.1
+
+### Bug Fixes
+
+- Fix for crashing range indexes when variable length is 1.  
+  [Łukasz Kuczborski](https://github.com/lkuczborski)
+  [#306](https://github.com/stencilproject/Stencil/pull/306)
+
+
+## 0.14.0
+
+### Breaking
+
+- Drop support for Swift < 4.2. For Swift 4 support, you should use Stencil 0.13.1.  
+  [David Jennes](https://github.com/djbe)
+  [#294](https://github.com/stencilproject/Stencil/pull/294)
+
+### Enhancements
+
+- Added support for dynamic filter using `filter` filter. With that you can define a variable with a name of filter
+, i.e. `myfilter = "uppercase"` and then use it to invoke this filter with `{{ string|filter:myfilter }}`.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#203](https://github.com/stencilproject/Stencil/pull/203)
+
+### Bug Fixes
+
+- Fixed using parenthesis in boolean expressions, they now can be used without spaces around them.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#254](https://github.com/stencilproject/Stencil/pull/254)
+- Throw syntax error on empty variable tags (`{{ }}`) instead `fatalError`.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#263](https://github.com/stencilproject/Stencil/pull/263)
+
+### Internal Changes
+
+- `Token` type converted to struct to allow computing token components only once.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#256](https://github.com/stencilproject/Stencil/pull/256)
+- Added SwiftLint to the project.  
+  [David Jennes](https://github.com/djbe)
+  [#249](https://github.com/stencilproject/Stencil/pull/249)
+- Updated to Swift 5.  
+  [Jungwon An](https://github.com/kawoou)
+  [#268](https://github.com/stencilproject/Stencil/pull/268)
+
+
+## 0.13.1
+
+### Bug Fixes
+
+- Fixed a bug in Stencil 0.13 where tags without spaces were incorrectly parsed.  
+  [David Jennes](https://github.com/djbe)
+  [#252](https://github.com/stencilproject/Stencil/pull/252)
+
+
+## 0.13.0
+
+### Breaking
+
+- Now requires Swift 4.1 or newer.  
+  [Yonas Kolb](https://github.com/yonaskolb)
+  [#228](https://github.com/stencilproject/Stencil/pull/228)
+
+### Enhancements
+
+- You can now use parentheses in boolean expressions to change operator precedence.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#165](https://github.com/stencilproject/Stencil/pull/165)
+- Added method to add boolean filters with their negative counterparts.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#160](https://github.com/stencilproject/Stencil/pull/160)
+- Now you can conditionally render variables with `{{ variable if condition }}`, which is a shorthand for `{% if condition %}{{ variable }}{% endif %}`. You can also use `else` like `{{ variable1 if condition else variable2 }}`, which is a shorthand for `{% if condition %}{{ variable1 }}{% else %}{{ variable2 }}{% endif %}`  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#243](https://github.com/stencilproject/Stencil/pull/243)
+- Now you can access string characters by index or get string length the same was as if it was an array, i.e. `{{ 'string'.first }}`, `{{ 'string'.last }}`, `{{ 'string'.1 }}`, `{{ 'string'.count }}`.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#245](https://github.com/stencilproject/Stencil/pull/245)
+
+### Bug Fixes
+
+- Fixed the performance issues introduced in Stencil 0.12 with the error log improvements.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#230](https://github.com/stencilproject/Stencil/pull/230)
+- Now accessing undefined keys in NSObject does not cause runtime crash and instead renders empty string.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#234](https://github.com/stencilproject/Stencil/pull/234)
+- `for` tag: When iterating over a dictionary the keys will now always be sorted (in an ascending order) to ensure consistent output generation.  
+  [David Jennes](https://github.com/djbe)
+  [#240](https://github.com/stencilproject/Stencil/pull/240)
+
+### Internal Changes
+
+- Updated the codebase to use Swift 4 features.  
+  [David Jennes](https://github.com/djbe)
+  [#239](https://github.com/stencilproject/Stencil/pull/239)
+- Update to Spectre 0.9.0.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#247](https://github.com/stencilproject/Stencil/pull/247)
+- Optimise Scanner performance.  
+  [Eric Thorpe](https://github.com/trametheka)
+  [Sébastien Duperron](https://github.com/Liquidsoul)
+  [David Jennes](https://github.com/djbe)
+  [#226](https://github.com/stencilproject/Stencil/pull/226)
+
+
+## 0.12.1
+
+### Internal Changes
+
+- Updated the PathKit dependency to 0.9.0 in CocoaPods, to be in line with SPM.  
+  [David Jennes](https://github.com/djbe)
+  [#227](https://github.com/stencilproject/Stencil/pull/227)
+
+
+## 0.12.0
+
+### Enhancements
+
+- Added an optional second parameter to the `include` tag for passing a sub context to the included file.  
+  [Yonas Kolb](https://github.com/yonaskolb)
+  [#214](https://github.com/stencilproject/Stencil/pull/214)
+- Variables now support the subscript notation. For example, if you have a variable `key = "name"`, and an
+  object `item = ["name": "John"]`, then `{{ item[key] }}` will evaluate to "John".  
+  [David Jennes](https://github.com/djbe)
+  [#215](https://github.com/stencilproject/Stencil/pull/215)
+- Adds support for using spaces in filter expression.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#178](https://github.com/stencilproject/Stencil/pull/178)
+- Improvements in error reporting.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#167](https://github.com/stencilproject/Stencil/pull/167)
+
+### Bug Fixes
+
+- Fixed using quote as a filter parameter.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#210](https://github.com/stencilproject/Stencil/pull/210)
+
+
+## 0.11.0 (2018-04-04)
+
+### Enhancements
+
+- Added support for resolving superclass properties for not-NSObject subclasses.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#152](https://github.com/stencilproject/Stencil/pull/152)
+- The `{% for %}` tag can now iterate over tuples, structures and classes via
+  their stored properties.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#173](https://github.com/stencilproject/Stencil/pull/173)
+- Added `split` filter.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#187](https://github.com/stencilproject/Stencil/pull/187)
+- Allow default string filters to be applied to arrays.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#190](https://github.com/stencilproject/Stencil/pull/190)
+- Similar filters are suggested when unknown filter is used.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#186](https://github.com/stencilproject/Stencil/pull/186)
+- Added `indent` filter.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#188](https://github.com/stencilproject/Stencil/pull/188)
+- Allow using new lines inside tags.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#202](https://github.com/stencilproject/Stencil/pull/202)
+- Added support for iterating arrays of tuples.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#177](https://github.com/stencilproject/Stencil/pull/177)
+- Added support for ranges in if-in expression.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#193](https://github.com/stencilproject/Stencil/pull/193)
+- Added property `forloop.length` to get number of items in the loop.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#171](https://github.com/stencilproject/Stencil/pull/171)
+- Now you can construct ranges for loops using `a...b` syntax, i.e. `for i in 1...array.count`.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#192](https://github.com/stencilproject/Stencil/pull/192)
+
+### Bug Fixes
+
+- Fixed rendering `{{ block.super }}` with several levels of inheritance.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#154](https://github.com/stencilproject/Stencil/pull/154)
+- Fixed checking dictionary values for nil in `default` filter.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#162](https://github.com/stencilproject/Stencil/pull/162)
+- Fixed comparing string variables with string literals, in Swift 4 string literals became `Substring` and thus couldn't be directly compared to strings.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#168](https://github.com/stencilproject/Stencil/pull/168)
+- Integer literals now resolve into Int values, not Float.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#181](https://github.com/stencilproject/Stencil/pull/181)
+- Fixed accessing properties of optional properties via reflection.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#204](https://github.com/stencilproject/Stencil/pull/204)
+- No longer render optional values in arrays as `Optional(..)`.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#205](https://github.com/stencilproject/Stencil/pull/205)
+- Fixed subscription tuples by value index, i.e. `{{ tuple.0 }}`.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#172](https://github.com/stencilproject/Stencil/pull/172)
+
 
 ## 0.10.1
 
@@ -55,7 +332,7 @@
 ### Bug Fixes
 
 - You can now use literal filter arguments which contain quotes.
-  [#98](https://github.com/kylef/Stencil/pull/98)
+  [#98](https://github.com/stencilproject/Stencil/pull/98)
 
 
 ## 0.8.0
@@ -198,11 +475,11 @@
 ### Bug Fixes
 
 - Variables (`{{ variable.5 }}`) that reference an array index at an unknown
-  index will now resolve to `nil` instead of causing a crash.
+  index will now resolve to `nil` instead of causing a crash.  
-  [#72](https://github.com/kylef/Stencil/issues/72)
+  [#72](https://github.com/stencilproject/Stencil/issues/72)
 
-- Templates can now extend templates that extend other templates.
+- Templates can now extend templates that extend other templates.  
-  [#60](https://github.com/kylef/Stencil/issues/60)
+  [#60](https://github.com/stencilproject/Stencil/issues/60)
 
 - If comparisons will now treat 0 and below numbers as negative.
 

Gemfile

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+source 'https://rubygems.org'
+
+# The bare minimum for building, e.g. in Homebrew
+group :build do
+  gem 'rake', '~> 13.0'
+  gem 'xcpretty', '~> 0.3'
+end
+
+# In addition to :build, for contributing
+group :development do
+  gem 'cocoapods', '~> 1.11'
+  gem 'danger', '~> 8.4'
+  gem 'rubocop', '~> 1.22'
+end
+
+# For releasing to GitHub
+group :release do
+  gem 'octokit', '~> 4.7'
+end

Gemfile.lock

@@ -0,0 +1,189 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    CFPropertyList (3.0.5)
+      rexml
+    activesupport (6.1.6.1)
+      concurrent-ruby (~> 1.0, >= 1.0.2)
+      i18n (>= 1.6, < 2)
+      minitest (>= 5.1)
+      tzinfo (~> 2.0)
+      zeitwerk (~> 2.3)
+    addressable (2.8.0)
+      public_suffix (>= 2.0.2, < 5.0)
+    algoliasearch (1.27.5)
+      httpclient (~> 2.8, >= 2.8.3)
+      json (>= 1.5.1)
+    ast (2.4.2)
+    atomos (0.1.3)
+    claide (1.1.0)
+    claide-plugins (0.9.2)
+      cork
+      nap
+      open4 (~> 1.3)
+    cocoapods (1.11.3)
+      addressable (~> 2.8)
+      claide (>= 1.0.2, < 2.0)
+      cocoapods-core (= 1.11.3)
+      cocoapods-deintegrate (>= 1.0.3, < 2.0)
+      cocoapods-downloader (>= 1.4.0, < 2.0)
+      cocoapods-plugins (>= 1.0.0, < 2.0)
+      cocoapods-search (>= 1.0.0, < 2.0)
+      cocoapods-trunk (>= 1.4.0, < 2.0)
+      cocoapods-try (>= 1.1.0, < 2.0)
+      colored2 (~> 3.1)
+      escape (~> 0.0.4)
+      fourflusher (>= 2.3.0, < 3.0)
+      gh_inspector (~> 1.0)
+      molinillo (~> 0.8.0)
+      nap (~> 1.0)
+      ruby-macho (>= 1.0, < 3.0)
+      xcodeproj (>= 1.21.0, < 2.0)
+    cocoapods-core (1.11.3)
+      activesupport (>= 5.0, < 7)
+      addressable (~> 2.8)
+      algoliasearch (~> 1.0)
+      concurrent-ruby (~> 1.1)
+      fuzzy_match (~> 2.0.4)
+      nap (~> 1.0)
+      netrc (~> 0.11)
+      public_suffix (~> 4.0)
+      typhoeus (~> 1.0)
+    cocoapods-deintegrate (1.0.5)
+    cocoapods-downloader (1.6.3)
+    cocoapods-plugins (1.0.0)
+      nap
+    cocoapods-search (1.0.1)
+    cocoapods-trunk (1.6.0)
+      nap (>= 0.8, < 2.0)
+      netrc (~> 0.11)
+    cocoapods-try (1.2.0)
+    colored2 (3.1.2)
+    concurrent-ruby (1.1.10)
+    cork (0.3.0)
+      colored2 (~> 3.1)
+    danger (8.6.1)
+      claide (~> 1.0)
+      claide-plugins (>= 0.9.2)
+      colored2 (~> 3.1)
+      cork (~> 0.1)
+      faraday (>= 0.9.0, < 2.0)
+      faraday-http-cache (~> 2.0)
+      git (~> 1.7)
+      kramdown (~> 2.3)
+      kramdown-parser-gfm (~> 1.0)
+      no_proxy_fix
+      octokit (~> 4.7)
+      terminal-table (>= 1, < 4)
+    escape (0.0.4)
+    ethon (0.15.0)
+      ffi (>= 1.15.0)
+    faraday (1.10.0)
+      faraday-em_http (~> 1.0)
+      faraday-em_synchrony (~> 1.0)
+      faraday-excon (~> 1.1)
+      faraday-httpclient (~> 1.0)
+      faraday-multipart (~> 1.0)
+      faraday-net_http (~> 1.0)
+      faraday-net_http_persistent (~> 1.0)
+      faraday-patron (~> 1.0)
+      faraday-rack (~> 1.0)
+      faraday-retry (~> 1.0)
+      ruby2_keywords (>= 0.0.4)
+    faraday-em_http (1.0.0)
+    faraday-em_synchrony (1.0.0)
+    faraday-excon (1.1.0)
+    faraday-http-cache (2.4.0)
+      faraday (>= 0.8)
+    faraday-httpclient (1.0.1)
+    faraday-multipart (1.0.4)
+      multipart-post (~> 2)
+    faraday-net_http (1.0.1)
+    faraday-net_http_persistent (1.2.0)
+    faraday-patron (1.0.0)
+    faraday-rack (1.0.0)
+    faraday-retry (1.0.3)
+    ffi (1.15.5)
+    fourflusher (2.3.1)
+    fuzzy_match (2.0.4)
+    gh_inspector (1.1.3)
+    git (1.11.0)
+      rchardet (~> 1.8)
+    httpclient (2.8.3)
+    i18n (1.12.0)
+      concurrent-ruby (~> 1.0)
+    json (2.6.2)
+    kramdown (2.4.0)
+      rexml
+    kramdown-parser-gfm (1.1.0)
+      kramdown (~> 2.0)
+    minitest (5.16.2)
+    molinillo (0.8.0)
+    multipart-post (2.2.3)
+    nanaimo (0.3.0)
+    nap (1.1.0)
+    netrc (0.11.0)
+    no_proxy_fix (0.1.2)
+    octokit (4.25.1)
+      faraday (>= 1, < 3)
+      sawyer (~> 0.9)
+    open4 (1.3.4)
+    parallel (1.22.1)
+    parser (3.1.2.0)
+      ast (~> 2.4.1)
+    public_suffix (4.0.7)
+    rainbow (3.1.1)
+    rake (13.0.6)
+    rchardet (1.8.0)
+    regexp_parser (2.5.0)
+    rexml (3.2.5)
+    rouge (2.0.7)
+    rubocop (1.32.0)
+      json (~> 2.3)
+      parallel (~> 1.10)
+      parser (>= 3.1.0.0)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 1.8, < 3.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.19.1, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 1.4.0, < 3.0)
+    rubocop-ast (1.19.1)
+      parser (>= 3.1.1.0)
+    ruby-macho (2.5.1)
+    ruby-progressbar (1.11.0)
+    ruby2_keywords (0.0.5)
+    sawyer (0.9.2)
+      addressable (>= 2.3.5)
+      faraday (>= 0.17.3, < 3)
+    terminal-table (3.0.2)
+      unicode-display_width (>= 1.1.1, < 3)
+    typhoeus (1.4.0)
+      ethon (>= 0.9.0)
+    tzinfo (2.0.5)
+      concurrent-ruby (~> 1.0)
+    unicode-display_width (2.2.0)
+    xcodeproj (1.22.0)
+      CFPropertyList (>= 2.3.3, < 4.0)
+      atomos (~> 0.1.3)
+      claide (>= 1.0.2, < 2.0)
+      colored2 (~> 3.1)
+      nanaimo (~> 0.3.0)
+      rexml (~> 3.2.4)
+    xcpretty (0.3.0)
+      rouge (~> 2.0.7)
+    zeitwerk (2.6.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  cocoapods (~> 1.11)
+  danger (~> 8.4)
+  octokit (~> 4.7)
+  rake (~> 13.0)
+  rubocop (~> 1.22)
+  xcpretty (~> 0.3)
+
+BUNDLED WITH
+   2.2.33

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2014, Kyle Fuller
+Copyright (c) 2022, Kyle Fuller
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -21,4 +21,3 @@ SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-

Package.resolved

@@ -0,0 +1,25 @@
+{
+  "object": {
+    "pins": [
+      {
+        "package": "PathKit",
+        "repositoryURL": "https://github.com/kylef/PathKit.git",
+        "state": {
+          "branch": null,
+          "revision": "3bfd2737b700b9a36565a8c94f4ad2b050a5e574",
+          "version": "1.0.1"
+        }
+      },
+      {
+        "package": "Spectre",
+        "repositoryURL": "https://github.com/kylef/Spectre.git",
+        "state": {
+          "branch": null,
+          "revision": "26cc5e9ae0947092c7139ef7ba612e34646086c7",
+          "version": "0.10.1"
+        }
+      }
+    ]
+  },
+  "version": 1
+}

Package.swift

@@ -1,11 +1,23 @@
+// swift-tools-version:5.0
 import PackageDescription
 
 let package = Package(
   name: "Stencil",
+  products: [
+    .library(name: "Stencil", targets: ["Stencil"])
+  ],
   dependencies: [
-    .Package(url: "https://github.com/kylef/PathKit.git", majorVersion: 0, minor: 8),
+    .package(url: "https://github.com/kylef/PathKit.git", from: "1.0.1"),
-
+    .package(url: "https://github.com/kylef/Spectre.git", from: "0.10.1")
-    // https://github.com/apple/swift-package-manager/pull/597
+  ],
-    .Package(url: "https://github.com/kylef/Spectre.git", majorVersion: 0, minor: 7),
+  targets: [
-  ]
+    .target(name: "Stencil", dependencies: [
+      "PathKit"
+    ]),
+    .testTarget(name: "StencilTests", dependencies: [
+      "Stencil",
+      "Spectre"
+    ])
+  ],
+  swiftLanguageVersions: [.v5]
 )

README.md

@@ -1,7 +1,5 @@
 # Stencil
 
-[![Build Status](https://travis-ci.org/kylef/Stencil.svg?branch=master)](https://travis-ci.org/kylef/Stencil)
-
 Stencil is a simple and powerful template language for Swift. It provides a
 syntax similar to Django and Mustache. If you're familiar with these, you will
 feel right at home with Stencil.
@@ -63,6 +61,14 @@ Resources to help you integrate Stencil into a Swift project:
 - [API Reference](http://stencil.fuller.li/en/latest/api.html)
 - [Custom Template Tags and Filters](http://stencil.fuller.li/en/latest/custom-template-tags-and-filters.html)
 
+## Projects that use Stencil
+
+[Sourcery](https://github.com/krzysztofzablocki/Sourcery),
+[SwiftGen](https://github.com/SwiftGen/SwiftGen),
+[Kitura](https://github.com/IBM-Swift/Kitura),
+[Weaver](https://github.com/scribd/Weaver),
+[Genesis](https://github.com/yonaskolb/Genesis)
+
 ## License
 
 Stencil is licensed under the BSD license. See [LICENSE](LICENSE) for more

Rakefile

@@ -0,0 +1,52 @@
+#!/usr/bin/rake
+
+unless defined?(Bundler)
+  puts 'Please use bundle exec to run the rake command'
+  exit 1
+end
+
+require 'English'
+
+## [ Constants ] ##############################################################
+
+POD_NAME = 'Stencil'
+MIN_XCODE_VERSION = 13.0
+BUILD_DIR = File.absolute_path('./.build')
+
+## [ Build Tasks ] ############################################################
+
+namespace :files do
+  desc 'Update all files containing a version'
+  task :update, [:version] do |_, args|
+    version = args[:version]
+
+    Utils.print_header "Updating files for version #{version}"
+
+    podspec = Utils.podspec(POD_NAME)
+    podspec['version'] = version
+    podspec['source']['tag'] = version
+    File.write("#{POD_NAME}.podspec.json", JSON.pretty_generate(podspec) + "\n")
+
+    replace('CHANGELOG.md', '## Master' => "\#\# #{version}")
+    replace("docs/conf.py",
+      /^version = .*/ => %Q(version = '#{version}'),
+      /^release = .*/ => %Q(release = '#{version}')
+    )
+    docs_package = Utils.first_match_in_file('docs/installation.rst', /\.package\(url: .+ from: "(.+)"/, 1)
+    replace("docs/installation.rst",
+      /\.package\(url: .+, from: "(.+)"/ => %Q(.package\(url: "https://github.com/stencilproject/Stencil.git", from: "#{version}"),
+      /pod 'Stencil', '.*'/ => %Q(pod 'Stencil', '~> #{version}'),
+      /github "stencilproject\/Stencil" ~> .*/ => %Q(github "stencilproject/Stencil" ~> #{version})
+    )
+  end
+
+  def replace(file, replacements)
+    content = File.read(file)
+    replacements.each do |match, replacement|
+      content.gsub!(match, replacement)
+    end
+    File.write(file, content)
+  end
+end
+
+task :default => 'release:new'

Sources/Context.swift

@@ -1,69 +0,0 @@
-/// A container for template variables.
-public class Context {
-  var dictionaries: [[String: Any?]]
-
-  public let environment: Environment
-
-  init(dictionary: [String: Any]? = nil, environment: Environment? = nil) {
-    if let dictionary = dictionary {
-      dictionaries = [dictionary]
-    } else {
-      dictionaries = []
-    }
-
-    self.environment = environment ?? Environment()
-  }
-
-  public subscript(key: String) -> Any? {
-    /// Retrieves a variable's value, starting at the current context and going upwards
-    get {
-      for dictionary in Array(dictionaries.reversed()) {
-        if let value = dictionary[key] {
-          return value
-        }
-      }
-
-      return nil
-    }
-
-    /// Set a variable in the current context, deleting the variable if it's nil
-    set(value) {
-      if let dictionary = dictionaries.popLast() {
-        var mutable_dictionary = dictionary
-        mutable_dictionary[key] = value
-        dictionaries.append(mutable_dictionary)
-      }
-    }
-  }
-
-  /// Push a new level into the Context
-  fileprivate func push(_ dictionary: [String: Any]? = nil) {
-    dictionaries.append(dictionary ?? [:])
-  }
-
-  /// Pop the last level off of the Context
-  fileprivate func pop() -> [String: Any?]? {
-    return dictionaries.popLast()
-  }
-
-  /// Push a new level onto the context for the duration of the execution of the given closure
-  public func push<Result>(dictionary: [String: Any]? = nil, closure: (() throws -> Result)) rethrows -> Result {
-    push(dictionary)
-    defer { _ = pop() }
-    return try closure()
-  }
-
-  public func flatten() -> [String: Any] {
-    var accumulator: [String: Any] = [:]
-
-    for dictionary in dictionaries {
-      for (key, value) in dictionary {
-        if let value = value {
-          accumulator.updateValue(value, forKey: key)
-        }
-      }
-    }
-
-    return accumulator
-  }
-}

Sources/Environment.swift

@@ -1,38 +0,0 @@
-public struct Environment {
-  public let templateClass: Template.Type
-  public var extensions: [Extension]
-
-  public var loader: Loader?
-
-  public init(loader: Loader? = nil, extensions: [Extension]? = nil, templateClass: Template.Type = Template.self) {
-    self.templateClass = templateClass
-    self.loader = loader
-    self.extensions = (extensions ?? []) + [DefaultExtension()]
-  }
-
-  public func loadTemplate(name: String) throws -> Template {
-    if let loader = loader {
-      return try loader.loadTemplate(name: name, environment: self)
-    } else {
-      throw TemplateDoesNotExist(templateNames: [name], loader: nil)
-    }
-  }
-
-  public func loadTemplate(names: [String]) throws -> Template {
-    if let loader = loader {
-      return try loader.loadTemplate(names: names, environment: self)
-    } else {
-      throw TemplateDoesNotExist(templateNames: names, loader: nil)
-    }
-  }
-
-  public func renderTemplate(name: String, context: [String: Any]? = nil) throws -> String {
-    let template = try loadTemplate(name: name)
-    return try template.render(context)
-  }
-
-  public func renderTemplate(string: String, context: [String: Any]? = nil) throws -> String {
-    let template = templateClass.init(templateString: string, environment: self)
-    return try template.render(context)
-  }
-}

Sources/Errors.swift

@@ -1,19 +0,0 @@
-public class TemplateDoesNotExist: Error, CustomStringConvertible {
-  let templateNames: [String]
-  let loader: Loader?
-
-  public init(templateNames: [String], loader: Loader? = nil) {
-    self.templateNames = templateNames
-    self.loader = loader
-  }
-
-  public var description: String {
-    let templates = templateNames.joined(separator: ", ")
-
-    if let loader = loader {
-      return "Template named `\(templates)` does not exist in loader \(loader)"
-    }
-
-    return "Template named `\(templates)` does not exist. No loaders found"
-  }
-}

Sources/Filters.swift

@@ -1,41 +0,0 @@
-func capitalise(_ value: Any?) -> Any? {
-  return stringify(value).capitalized
-}
-
-func uppercase(_ value: Any?) -> Any? {
-  return stringify(value).uppercased()
-}
-
-func lowercase(_ value: Any?) -> Any? {
-  return stringify(value).lowercased()
-}
-
-func defaultFilter(value: Any?, arguments: [Any?]) -> Any? {
-  if let value = value {
-    return value
-  }
-
-  for argument in arguments {
-    if let argument = argument {
-      return argument
-    }
-  }
-
-  return nil
-}
-
-func joinFilter(value: Any?, arguments: [Any?]) throws -> Any? {
-  guard arguments.count < 2 else {
-    throw TemplateSyntaxError("'join' filter takes a single argument")
-  }
-
-  let separator = stringify(arguments.first ?? "")
-
-  if let value = value as? [Any] {
-    return value
-      .map(stringify)
-      .joined(separator: separator)
-  }
-
-  return value
-}

Sources/ForTag.swift

@@ -1,132 +0,0 @@
-import Foundation
-
-class ForNode : NodeType {
-  let resolvable: Resolvable
-  let loopVariables: [String]
-  let nodes:[NodeType]
-  let emptyNodes: [NodeType]
-  let `where`: Expression?
-
-  class func parse(_ parser:TokenParser, token:Token) throws -> NodeType {
-    let components = token.components()
-
-    guard components.count >= 3 && components[2] == "in" &&
-        (components.count == 4 || (components.count >= 6 && components[4] == "where")) else {
-      throw TemplateSyntaxError("'for' statements should use the following 'for x in y where condition' `\(token.contents)`.")
-    }
-
-    let loopVariables = components[1].characters
-      .split(separator: ",")
-      .map(String.init)
-      .map { $0.trimmingCharacters(in: CharacterSet.whitespaces) }
-
-    let variable = components[3]
-
-    var emptyNodes = [NodeType]()
-
-    let forNodes = try parser.parse(until(["endfor", "empty"]))
-
-    guard let token = parser.nextToken() else {
-      throw TemplateSyntaxError("`endfor` was not found.")
-    }
-
-    if token.contents == "empty" {
-      emptyNodes = try parser.parse(until(["endfor"]))
-      _ = parser.nextToken()
-    }
-
-    let filter = try parser.compileFilter(variable)
-    let `where`: Expression?
-    if components.count >= 6 {
-      `where` = try parseExpression(components: Array(components.suffix(from: 5)), tokenParser: parser)
-    } else {
-      `where` = nil
-    }
-    return ForNode(resolvable: filter, loopVariables: loopVariables, nodes: forNodes, emptyNodes:emptyNodes, where: `where`)
-  }
-
-  init(resolvable: Resolvable, loopVariables: [String], nodes:[NodeType], emptyNodes:[NodeType], where: Expression? = nil) {
-    self.resolvable = resolvable
-    self.loopVariables = loopVariables
-    self.nodes = nodes
-    self.emptyNodes = emptyNodes
-    self.where = `where`
-  }
-
-  func push<Result>(value: Any, context: Context, closure: () throws -> (Result)) rethrows -> Result {
-    if loopVariables.isEmpty {
-      return try context.push() {
-        return try closure()
-      }
-    }
-
-    if let value = value as? (Any, Any) {
-      let first = loopVariables[0]
-
-      if loopVariables.count == 2 {
-        let second = loopVariables[1]
-
-        return try context.push(dictionary: [first: value.0, second: value.1]) {
-          return try closure()
-        }
-      }
-
-      return try context.push(dictionary: [first: value.0]) {
-        return try closure()
-      }
-    }
-
-    return try context.push(dictionary: [loopVariables.first!: value]) {
-      return try closure()
-    }
-  }
-
-  func render(_ context: Context) throws -> String {
-    let resolved = try resolvable.resolve(context)
-
-    var values: [Any]
-
-    if let dictionary = resolved as? [String: Any], !dictionary.isEmpty {
-      values = dictionary.map { ($0.key, $0.value) }
-    } else if let array = resolved as? [Any] {
-      values = array
-    } else if let range = resolved as? CountableClosedRange<Int> {
-      values = Array(range)
-    } else if let range = resolved as? CountableRange<Int> {
-      values = Array(range)
-    } else {
-      values = []
-    }
-
-    if let `where` = self.where {
-      values = try values.filter({ item -> Bool in
-        return try push(value: item, context: context) {
-          try `where`.evaluate(context: context)
-        }
-      })
-    }
-
-    if !values.isEmpty {
-      let count = values.count
-
-      return try values.enumerated().map { index, item in
-        let forContext: [String: Any] = [
-          "first": index == 0,
-          "last": index == (count - 1),
-          "counter": index + 1,
-          "counter0": index,
-        ]
-
-        return try context.push(dictionary: ["forloop": forContext]) {
-          return try push(value: item, context: context) {
-            try renderNodes(nodes, context)
-          }
-        }
-      }.joined(separator: "")
-    }
-
-    return try context.push {
-      try renderNodes(emptyNodes, context)
-    }
-  }
-}

Sources/IfTag.swift

@@ -1,265 +0,0 @@
-enum Operator {
-  case infix(String, Int, InfixOperator.Type)
-  case prefix(String, Int, PrefixOperator.Type)
-
-  var name: String {
-    switch self {
-    case .infix(let name, _, _):
-      return name
-    case .prefix(let name, _, _):
-      return name
-    }
-  }
-}
-
-
-let operators: [Operator] = [
-  .infix("in", 5, InExpression.self),
-  .infix("or", 6, OrExpression.self),
-  .infix("and", 7, AndExpression.self),
-  .prefix("not", 8, NotExpression.self),
-  .infix("==", 10, EqualityExpression.self),
-  .infix("!=", 10, InequalityExpression.self),
-  .infix(">", 10, MoreThanExpression.self),
-  .infix(">=", 10, MoreThanEqualExpression.self),
-  .infix("<", 10, LessThanExpression.self),
-  .infix("<=", 10, LessThanEqualExpression.self),
-]
-
-
-func findOperator(name: String) -> Operator? {
-  for op in operators {
-    if op.name == name {
-      return op
-    }
-  }
-
-  return nil
-}
-
-
-enum IfToken {
-  case infix(name: String, bindingPower: Int, op: InfixOperator.Type)
-  case prefix(name: String, bindingPower: Int, op: PrefixOperator.Type)
-  case variable(Resolvable)
-  case end
-
-  var bindingPower: Int {
-    switch self {
-    case .infix(_, let bindingPower, _):
-      return bindingPower
-    case .prefix(_, let bindingPower, _):
-      return bindingPower
-    case .variable(_):
-      return 0
-    case .end:
-        return 0
-    }
-  }
-
-  func nullDenotation(parser: IfExpressionParser) throws -> Expression {
-    switch self {
-    case .infix(let name, _, _):
-      throw TemplateSyntaxError("'if' expression error: infix operator '\(name)' doesn't have a left hand side")
-    case .prefix(_, let bindingPower, let op):
-      let expression = try parser.expression(bindingPower: bindingPower)
-      return op.init(expression: expression)
-    case .variable(let variable):
-      return VariableExpression(variable: variable)
-    case .end:
-      throw TemplateSyntaxError("'if' expression error: end")
-    }
-  }
-
-  func leftDenotation(left: Expression, parser: IfExpressionParser) throws -> Expression {
-    switch self {
-    case .infix(_, let bindingPower, let op):
-      let right = try parser.expression(bindingPower: bindingPower)
-      return op.init(lhs: left, rhs: right)
-    case .prefix(let name, _, _):
-      throw TemplateSyntaxError("'if' expression error: prefix operator '\(name)' was called with a left hand side")
-    case .variable(let variable):
-      throw TemplateSyntaxError("'if' expression error: variable '\(variable)' was called with a left hand side")
-    case .end:
-      throw TemplateSyntaxError("'if' expression error: end")
-    }
-  }
-
-  var isEnd: Bool {
-    switch self {
-    case .end:
-      return true
-    default:
-      return false
-    }
-  }
-}
-
-
-final class IfExpressionParser {
-  let tokens: [IfToken]
-  var position: Int = 0
-
-  init(components: [String], tokenParser: TokenParser) throws {
-    self.tokens = try components.map { component in
-      if let op = findOperator(name: component) {
-        switch op {
-        case .infix(let name, let bindingPower, let cls):
-          return .infix(name: name, bindingPower: bindingPower, op: cls)
-        case .prefix(let name, let bindingPower, let cls):
-          return .prefix(name: name, bindingPower: bindingPower, op: cls)
-        }
-      }
-
-      return .variable(try tokenParser.compileFilter(component))
-    }
-  }
-
-  var currentToken: IfToken {
-    if tokens.count > position {
-      return tokens[position]
-    }
-
-    return .end
-  }
-
-  var nextToken: IfToken {
-    position += 1
-    return currentToken
-  }
-
-  func parse() throws -> Expression {
-    let expression = try self.expression()
-
-    if !currentToken.isEnd {
-      throw TemplateSyntaxError("'if' expression error: dangling token")
-    }
-
-    return expression
-  }
-
-  func expression(bindingPower: Int = 0) throws -> Expression {
-    var token = currentToken
-    position += 1
-
-    var left = try token.nullDenotation(parser: self)
-
-    while bindingPower < currentToken.bindingPower {
-      token = currentToken
-      position += 1
-      left = try token.leftDenotation(left: left, parser: self)
-    }
-
-    return left
-  }
-}
-
-
-func parseExpression(components: [String], tokenParser: TokenParser) throws -> Expression {
-  let parser = try IfExpressionParser(components: components, tokenParser: tokenParser)
-  return try parser.parse()
-}
-
-
-/// Represents an if condition and the associated nodes when the condition
-/// evaluates
-final class IfCondition {
-  let expression: Expression?
-  let nodes: [NodeType]
-
-  init(expression: Expression?, nodes: [NodeType]) {
-    self.expression = expression
-    self.nodes = nodes
-  }
-
-  func render(_ context: Context) throws -> String {
-    return try context.push {
-      return try renderNodes(nodes, context)
-    }
-  }
-}
-
-
-class IfNode : NodeType {
-  let conditions: [IfCondition]
-
-  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
-    var components = token.components()
-    components.removeFirst()
-
-    let expression = try parseExpression(components: components, tokenParser: parser)
-    let nodes = try parser.parse(until(["endif", "elif", "else"]))
-    var conditions: [IfCondition] = [
-      IfCondition(expression: expression, nodes: nodes)
-    ]
-
-    var token = parser.nextToken()
-    while let current = token, current.contents.hasPrefix("elif") {
-      var components = current.components()
-      components.removeFirst()
-      let expression = try parseExpression(components: components, tokenParser: parser)
-
-      let nodes = try parser.parse(until(["endif", "elif", "else"]))
-      token = parser.nextToken()
-      conditions.append(IfCondition(expression: expression, nodes: nodes))
-    }
-
-    if let current = token, current.contents == "else" {
-      conditions.append(IfCondition(expression: nil, nodes: try parser.parse(until(["endif"]))))
-      token = parser.nextToken()
-    }
-
-    guard let current = token, current.contents == "endif" else {
-      throw TemplateSyntaxError("`endif` was not found.")
-    }
-
-    return IfNode(conditions: conditions)
-  }
-
-  class func parse_ifnot(_ parser: TokenParser, token: Token) throws -> NodeType {
-    var components = token.components()
-    guard components.count == 2 else {
-      throw TemplateSyntaxError("'ifnot' statements should use the following 'ifnot condition' `\(token.contents)`.")
-    }
-    components.removeFirst()
-    var trueNodes = [NodeType]()
-    var falseNodes = [NodeType]()
-
-    falseNodes = try parser.parse(until(["endif", "else"]))
-
-    guard let token = parser.nextToken() else {
-      throw TemplateSyntaxError("`endif` was not found.")
-    }
-
-    if token.contents == "else" {
-      trueNodes = try parser.parse(until(["endif"]))
-      _ = parser.nextToken()
-    }
-
-    let expression = try parseExpression(components: components, tokenParser: parser)
-    return IfNode(conditions: [
-      IfCondition(expression: expression, nodes: trueNodes),
-      IfCondition(expression: nil, nodes: falseNodes),
-    ])
-  }
-
-  init(conditions: [IfCondition]) {
-    self.conditions = conditions
-  }
-
-  func render(_ context: Context) throws -> String {
-    for condition in conditions {
-      if let expression = condition.expression {
-        let truthy = try expression.evaluate(context: context)
-
-        if truthy {
-          return try condition.render(context)
-        }
-      } else {
-        return try condition.render(context)
-      }
-    }
-
-    return ""
-  }
-}

Sources/Include.swift

@@ -1,33 +0,0 @@
-import PathKit
-
-
-class IncludeNode : NodeType {
-  let templateName: Variable
-
-  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
-    let bits = token.components()
-
-    guard bits.count == 2 else {
-      throw TemplateSyntaxError("'include' tag takes one argument, the template file to be included")
-    }
-
-    return IncludeNode(templateName: Variable(bits[1]))
-  }
-
-  init(templateName: Variable) {
-    self.templateName = templateName
-  }
-
-  func render(_ context: Context) throws -> String {
-    guard let templateName = try self.templateName.resolve(context) as? String else {
-      throw TemplateSyntaxError("'\(self.templateName)' could not be resolved as a string")
-    }
-
-    let template = try context.environment.loadTemplate(name: templateName)
-
-    return try context.push {
-      return try template.render(context)
-    }
-  }
-}
-

Sources/Inheritence.swift

@@ -1,119 +0,0 @@
-class BlockContext {
-  class var contextKey: String { return "block_context" }
-
-  var blocks: [String: BlockNode]
-
-  init(blocks: [String: BlockNode]) {
-    self.blocks = blocks
-  }
-
-  func pop(_ blockName: String) -> BlockNode? {
-    return blocks.removeValue(forKey: blockName)
-  }
-}
-
-
-extension Collection {
-  func any(_ closure: (Iterator.Element) -> Bool) -> Iterator.Element? {
-    for element in self {
-      if closure(element) {
-        return element
-      }
-    }
-
-    return nil
-  }
-}
-
-
-class ExtendsNode : NodeType {
-  let templateName: Variable
-  let blocks: [String:BlockNode]
-
-  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
-    let bits = token.components()
-
-    guard bits.count == 2 else {
-      throw TemplateSyntaxError("'extends' takes one argument, the template file to be extended")
-    }
-
-    let parsedNodes = try parser.parse()
-    guard (parsedNodes.any { $0 is ExtendsNode }) == nil else {
-      throw TemplateSyntaxError("'extends' cannot appear more than once in the same template")
-    }
-
-    let blockNodes = parsedNodes.flatMap { $0 as? BlockNode }
-
-    let nodes = blockNodes.reduce([String: BlockNode]()) { (accumulator, node) -> [String: BlockNode] in
-      var dict = accumulator
-      dict[node.name] = node
-      return dict
-    }
-
-    return ExtendsNode(templateName: Variable(bits[1]), blocks: nodes)
-  }
-
-  init(templateName: Variable, blocks: [String: BlockNode]) {
-    self.templateName = templateName
-    self.blocks = blocks
-  }
-
-  func render(_ context: Context) throws -> String {
-    guard let templateName = try self.templateName.resolve(context) as? String else {
-      throw TemplateSyntaxError("'\(self.templateName)' could not be resolved as a string")
-    }
-
-    let template = try context.environment.loadTemplate(name: templateName)
-
-    let blockContext: BlockContext
-    if let context = context[BlockContext.contextKey] as? BlockContext {
-      blockContext = context
-
-      for (key, value) in blocks {
-        if !blockContext.blocks.keys.contains(key) {
-          blockContext.blocks[key] = value
-        }
-      }
-    } else {
-      blockContext = BlockContext(blocks: blocks)
-    }
-
-    return try context.push(dictionary: [BlockContext.contextKey: blockContext]) {
-      return try template.render(context)
-    }
-  }
-}
-
-
-class BlockNode : NodeType {
-  let name: String
-  let nodes: [NodeType]
-
-  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
-    let bits = token.components()
-
-    guard bits.count == 2 else {
-      throw TemplateSyntaxError("'block' tag takes one argument, the block name")
-    }
-
-    let blockName = bits[1]
-    let nodes = try parser.parse(until(["endblock"]))
-    _ = parser.nextToken()
-    return BlockNode(name:blockName, nodes:nodes)
-  }
-
-  init(name: String, nodes: [NodeType]) {
-    self.name = name
-    self.nodes = nodes
-  }
-
-  func render(_ context: Context) throws -> String {
-    if let blockContext = context[BlockContext.contextKey] as? BlockContext, let node = blockContext.pop(name) {
-      return try context.push(dictionary: ["block": ["super": self]]) {
-        return try node.render(context)
-      }
-    }
-
-    return try renderNodes(nodes, context)
-  }
-}

Sources/Lexer.swift

@@ -1,154 +0,0 @@
-struct Lexer {
-  let templateString: String
-
-  init(templateString: String) {
-    self.templateString = templateString
-  }
-
-  func createToken(string: String) -> Token {
-    func strip() -> String {
-      guard string.characters.count > 4 else { return "" }
-      let start = string.index(string.startIndex, offsetBy: 2)
-      let end = string.index(string.endIndex, offsetBy: -2)
-      return String(string[start..<end]).trim(character: " ")
-    }
-
-    if string.hasPrefix("{{") {
-      return .variable(value: strip())
-    } else if string.hasPrefix("{%") {
-      return .block(value: strip())
-    } else if string.hasPrefix("{#") {
-      return .comment(value: strip())
-    }
-
-    return .text(value: string)
-  }
-
-  /// Returns an array of tokens from a given template string.
-  func tokenize() -> [Token] {
-    var tokens: [Token] = []
-
-    let scanner = Scanner(templateString)
-
-    let map = [
-      "{{": "}}",
-      "{%": "%}",
-      "{#": "#}",
-    ]
-
-    while !scanner.isEmpty {
-      if let text = scanner.scan(until: ["{{", "{%", "{#"]) {
-        if !text.1.isEmpty {
-          tokens.append(createToken(string: text.1))
-        }
-
-        let end = map[text.0]!
-        let result = scanner.scan(until: end, returnUntil: true)
-        tokens.append(createToken(string: result))
-      } else {
-        tokens.append(createToken(string: scanner.content))
-        scanner.content = ""
-      }
-    }
-
-    return tokens
-  }
-}
-
-
-class Scanner {
-  var content: String
-
-  init(_ content: String) {
-    self.content = content
-  }
-
-  var isEmpty: Bool {
-    return content.isEmpty
-  }
-
-  func scan(until: String, returnUntil: Bool = false) -> String {
-    if until.isEmpty {
-      return ""
-    }
-
-    var index = content.startIndex
-    while index != content.endIndex {
-      let substring = content.substring(from: index)
-
-      if substring.hasPrefix(until) {
-        let result = content.substring(to: index)
-        content = substring
-
-        if returnUntil {
-          content = content.substring(from: until.endIndex)
-          return result + until
-        }
-
-        return result
-      }
-
-      index = content.index(after: index)
-    }
-
-    content = ""
-    return ""
-  }
-
-  func scan(until: [String]) -> (String, String)? {
-    if until.isEmpty {
-      return nil
-    }
-
-    var index = content.startIndex
-    while index != content.endIndex {
-      let substring = content.substring(from: index)
-      for string in until {
-        if substring.hasPrefix(string) {
-          let result = content.substring(to: index)
-          content = substring
-          return (string, result)
-        }
-      }
-
-      index = content.index(after: index)
-    }
-
-    return nil
-  }
-}
-
-
-extension String {
-  func findFirstNot(character: Character) -> String.Index? {
-    var index = startIndex
-
-    while index != endIndex {
-      if character != self[index] {
-        return index
-      }
-      index = self.index(after: index)
-    }
-
-    return nil
-  }
-
-  func findLastNot(character: Character) -> String.Index? {
-    var index = self.index(before: endIndex)
-
-    while index != startIndex {
-      if character != self[index] {
-        return self.index(after: index)
-      }
-      index = self.index(before: index)
-    }
-
-    return nil
-  }
-
-  func trim(character: Character) -> String {
-    let first = findFirstNot(character: character) ?? startIndex
-    let last = findLastNot(character: character) ?? endIndex
-    return String(self[first..<last])
-  }
-}

Sources/Node.swift

@@ -1,88 +0,0 @@
-import Foundation
-
-
-public struct TemplateSyntaxError : Error, Equatable, CustomStringConvertible {
-  public let description:String
-
-  public init(_ description:String) {
-    self.description = description
-  }
-}
-
-
-public func ==(lhs:TemplateSyntaxError, rhs:TemplateSyntaxError) -> Bool {
-  return lhs.description == rhs.description
-}
-
-
-public protocol NodeType {
-  /// Render the node in the given context
-  func render(_ context:Context) throws -> String
-}
-
-
-/// Render the collection of nodes in the given context
-public func renderNodes(_ nodes:[NodeType], _ context:Context) throws -> String {
-  return try nodes.map { try $0.render(context) }.joined(separator: "")
-}
-
-public class SimpleNode : NodeType {
-  public let handler:(Context) throws -> String
-
-  public init(handler: @escaping (Context) throws -> String) {
-    self.handler = handler
-  }
-
-  public func render(_ context: Context) throws -> String {
-    return try handler(context)
-  }
-}
-
-
-public class TextNode : NodeType {
-  public let text:String
-
-  public init(text:String) {
-    self.text = text
-  }
-
-  public func render(_ context:Context) throws -> String {
-    return self.text
-  }
-}
-
-
-public protocol Resolvable {
-  func resolve(_ context: Context) throws -> Any?
-}
-
-
-public class VariableNode : NodeType {
-  public let variable: Resolvable
-
-  public init(variable: Resolvable) {
-    self.variable = variable
-  }
-
-  public init(variable: String) {
-    self.variable = Variable(variable)
-  }
-
-  public func render(_ context: Context) throws -> String {
-    let result = try variable.resolve(context)
-    return stringify(result)
-  }
-}
-
-
-func stringify(_ result: Any?) -> String {
-  if let result = result as? String {
-    return result
-  } else if let result = result as? CustomStringConvertible {
-    return result.description
-  } else if let result = result as? NSObject {
-    return result.description
-  }
-
-  return ""
-}

Sources/Parser.swift

@@ -1,98 +0,0 @@
-public func until(_ tags: [String]) -> ((TokenParser, Token) -> Bool) {
-  return { parser, token in
-    if let name = token.components().first {
-      for tag in tags {
-        if name == tag {
-          return true
-        }
-      }
-    }
-
-    return false
-  }
-}
-
-
-/// A class for parsing an array of tokens and converts them into a collection of Node's
-public class TokenParser {
-  public typealias TagParser = (TokenParser, Token) throws -> NodeType
-
-  fileprivate var tokens: [Token]
-  fileprivate let environment: Environment
-
-  public init(tokens: [Token], environment: Environment) {
-    self.tokens = tokens
-    self.environment = environment
-  }
-
-  /// Parse the given tokens into nodes
-  public func parse() throws -> [NodeType] {
-    return try parse(nil)
-  }
-
-  public func parse(_ parse_until:((_ parser:TokenParser, _ token:Token) -> (Bool))?) throws -> [NodeType] {
-    var nodes = [NodeType]()
-
-    while tokens.count > 0 {
-      let token = nextToken()!
-
-      switch token {
-      case .text(let text):
-        nodes.append(TextNode(text: text))
-      case .variable:
-        nodes.append(VariableNode(variable: try compileFilter(token.contents)))
-      case .block:
-        if let parse_until = parse_until , parse_until(self, token) {
-          prependToken(token)
-          return nodes
-        }
-
-        if let tag = token.components().first {
-          let parser = try findTag(name: tag)
-          nodes.append(try parser(self, token))
-        }
-      case .comment:
-        continue
-      }
-    }
-
-    return nodes
-  }
-
-  public func nextToken() -> Token? {
-    if tokens.count > 0 {
-      return tokens.remove(at: 0)
-    }
-
-    return nil
-  }
-
-  public func prependToken(_ token:Token) {
-    tokens.insert(token, at: 0)
-  }
-
-  func findTag(name: String) throws -> Extension.TagParser {
-    for ext in environment.extensions {
-      if let filter = ext.tags[name] {
-        return filter
-      }
-    }
-
-    throw TemplateSyntaxError("Unknown template tag '\(name)'")
-  }
-
-  func findFilter(_ name: String) throws -> FilterType {
-    for ext in environment.extensions {
-      if let filter = ext.filters[name] {
-        return filter
-      }
-    }
-
-    throw TemplateSyntaxError("Unknown filter '\(name)'")
-  }
-
-  public func compileFilter(_ token: String) throws -> Resolvable {
-    return try FilterExpression(token: token, parser: self)
-  }
-
-}

Sources/Stencil/Context.swift

@@ -0,0 +1,111 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+/// A container for template variables.
+public class Context {
+  var dictionaries: [[String: Any?]]
+
+  /// The context's environment, such as registered extensions, classes, …
+  public let environment: Environment
+
+  init(dictionaries: [[String: Any?]], environment: Environment) {
+    self.dictionaries = dictionaries
+    self.environment = environment
+  }
+
+  /// Create a context from a dictionary (and an env.)
+  ///
+  /// - Parameters:
+  ///   - dictionary: The context's data
+  ///   - environment: Environment such as extensions, …
+  public convenience init(dictionary: [String: Any] = [:], environment: Environment? = nil) {
+    self.init(
+      dictionaries: dictionary.isEmpty ? [] : [dictionary],
+      environment: environment ?? Environment()
+    )
+  }
+
+  /// Access variables in this context by name
+  public subscript(key: String) -> Any? {
+    /// Retrieves a variable's value, starting at the current context and going upwards
+    get {
+      for dictionary in Array(dictionaries.reversed()) {
+        if let value = dictionary[key] {
+          return value
+        }
+      }
+
+      return nil
+    }
+
+    /// Set a variable in the current context, deleting the variable if it's nil
+    set(value) {
+      if var dictionary = dictionaries.popLast() {
+        dictionary[key] = value
+        dictionaries.append(dictionary)
+      }
+    }
+  }
+
+  /// Push a new level into the Context
+  ///
+  /// - Parameters:
+  ///   - dictionary: The new level data
+  fileprivate func push(_ dictionary: [String: Any] = [:]) {
+    dictionaries.append(dictionary)
+  }
+
+  /// Pop the last level off of the Context
+  ///
+  /// - returns: The popped level
+  fileprivate func pop() -> [String: Any?]? {
+    dictionaries.popLast()
+  }
+
+  /// Push a new level onto the context for the duration of the execution of the given closure
+  ///
+  /// - Parameters:
+  ///   - dictionary: The new level data
+  ///   - closure: The closure to execute
+  /// - returns: Return value of the closure
+  public func push<Result>(dictionary: [String: Any] = [:], closure: (() throws -> Result)) rethrows -> Result {
+    push(dictionary)
+    defer { _ = pop() }
+    return try closure()
+  }
+
+  /// Flatten all levels of context data into 1, merging duplicate variables
+  /// 
+  /// - returns: All collected variables
+  public func flatten() -> [String: Any] {
+    var accumulator: [String: Any] = [:]
+
+    for dictionary in dictionaries {
+      for (key, value) in dictionary {
+        if let value = value {
+          accumulator.updateValue(value, forKey: key)
+        }
+      }
+    }
+
+    return accumulator
+  }
+
+  /// Cache result of block by its name in the context top-level, so that it can be later rendered
+  /// via `{{ block.name }}`
+  ///
+  /// - Parameters:
+  ///   - name: The name of the stored block
+  ///   - content: The block's rendered content
+  public func cacheBlock(_ name: String, content: String) {
+    if var block = dictionaries.first?["block"] as? [String: String] {
+      block[name] = content
+      dictionaries[0]["block"] = block
+    } else {
+      dictionaries.insert(["block": [name: content]], at: 0)
+    }
+  }
+}

Sources/Stencil/DynamicMemberLookup.swift

@@ -0,0 +1,24 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+/// Marker protocol so we can know which types support `@dynamicMemberLookup`. Add this to your own types that support
+/// lookup by String.
+public protocol DynamicMemberLookup {
+  /// Get a value for a given `String` key
+  subscript(dynamicMember member: String) -> Any? { get }
+}
+
+public extension DynamicMemberLookup where Self: RawRepresentable {
+  /// Get a value for a given `String` key
+  subscript(dynamicMember member: String) -> Any? {
+    switch member {
+    case "rawValue":
+      return rawValue
+    default:
+      return nil
+    }
+  }
+}

Sources/Stencil/Environment.swift

@@ -0,0 +1,90 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+/// Container for environment data, such as registered extensions
+public struct Environment {
+  /// The class for loading new templates
+  public let templateClass: Template.Type
+  /// List of registered extensions
+  public var extensions: [Extension]
+  /// How to handle whitespace
+  public var trimBehaviour: TrimBehaviour
+  /// Mechanism for loading new files
+  public var loader: Loader?
+
+  /// Basic initializer
+  ///
+  /// - Parameters:
+  ///  - loader: Mechanism for loading new files
+  ///  - extensions: List of extension containers
+  ///  - templateClass: Class for newly loaded templates
+  ///  - trimBehaviour: How to handle whitespace
+  public init(
+    loader: Loader? = nil,
+    extensions: [Extension] = [],
+    templateClass: Template.Type = Template.self,
+    trimBehaviour: TrimBehaviour = .nothing
+  ) {
+    self.templateClass = templateClass
+    self.loader = loader
+    self.extensions = extensions + [DefaultExtension()]
+    self.trimBehaviour = trimBehaviour
+  }
+
+  /// Load a template with the given name
+  ///
+  /// - Parameters:
+  ///  - name: Name of the template
+  /// - returns: Loaded template instance
+  public func loadTemplate(name: String) throws -> Template {
+    if let loader = loader {
+      return try loader.loadTemplate(name: name, environment: self)
+    } else {
+      throw TemplateDoesNotExist(templateNames: [name], loader: nil)
+    }
+  }
+
+  /// Load a template with the given names
+  ///
+  /// - Parameters:
+  ///  - names: Names of the template
+  /// - returns: Loaded template instance
+  public func loadTemplate(names: [String]) throws -> Template {
+    if let loader = loader {
+      return try loader.loadTemplate(names: names, environment: self)
+    } else {
+      throw TemplateDoesNotExist(templateNames: names, loader: nil)
+    }
+  }
+
+  /// Render a template with the given name, providing some data
+  ///
+  /// - Parameters:
+  ///  - name: Name of the template
+  ///  - context: Data for rendering
+  /// - returns: Rendered output
+  public func renderTemplate(name: String, context: [String: Any] = [:]) throws -> String {
+    let template = try loadTemplate(name: name)
+    return try render(template: template, context: context)
+  }
+
+  /// Render the given template string, providing some data
+  ///
+  /// - Parameters:
+  ///  - string: Template string
+  ///  - context: Data for rendering
+  /// - returns: Rendered output
+  public func renderTemplate(string: String, context: [String: Any] = [:]) throws -> String {
+    let template = templateClass.init(templateString: string, environment: self)
+    return try render(template: template, context: context)
+  }
+
+  func render(template: Template, context: [String: Any]) throws -> String {
+    // update template environment as it can be created from string literal with default environment
+    template.environment = self
+    return try template.render(context)
+  }
+}

Sources/Stencil/Errors.swift

@@ -0,0 +1,87 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+public class TemplateDoesNotExist: Error, CustomStringConvertible {
+  let templateNames: [String]
+  let loader: Loader?
+
+  public init(templateNames: [String], loader: Loader? = nil) {
+    self.templateNames = templateNames
+    self.loader = loader
+  }
+
+  public var description: String {
+    let templates = templateNames.joined(separator: ", ")
+
+    if let loader = loader {
+      return "Template named `\(templates)` does not exist in loader \(loader)"
+    }
+
+    return "Template named `\(templates)` does not exist. No loaders found"
+  }
+}
+
+public struct TemplateSyntaxError: Error, Equatable, CustomStringConvertible {
+  public let reason: String
+  public var description: String { reason }
+  public internal(set) var token: Token?
+  public internal(set) var stackTrace: [Token]
+  public var templateName: String? { token?.sourceMap.filename }
+  var allTokens: [Token] {
+    stackTrace + (token.map { [$0] } ?? [])
+  }
+
+  public init(reason: String, token: Token? = nil, stackTrace: [Token] = []) {
+    self.reason = reason
+    self.stackTrace = stackTrace
+    self.token = token
+  }
+
+  public init(_ description: String) {
+    self.init(reason: description)
+  }
+}
+
+extension Error {
+  func withToken(_ token: Token?) -> Error {
+    if var error = self as? TemplateSyntaxError {
+      error.token = error.token ?? token
+      return error
+    } else {
+      return TemplateSyntaxError(reason: "\(self)", token: token)
+    }
+  }
+}
+
+public protocol ErrorReporter: AnyObject {
+  func renderError(_ error: Error) -> String
+}
+
+open class SimpleErrorReporter: ErrorReporter {
+  open func renderError(_ error: Error) -> String {
+    guard let templateError = error as? TemplateSyntaxError else { return error.localizedDescription }
+
+    func describe(token: Token) -> String {
+      let templateName = token.sourceMap.filename ?? ""
+      let location = token.sourceMap.location
+      let highlight = """
+        \(String(Array(repeating: " ", count: location.lineOffset)))\
+        ^\(String(Array(repeating: "~", count: max(token.contents.count - 1, 0))))
+        """
+
+      return """
+        \(templateName)\(location.lineNumber):\(location.lineOffset): error: \(templateError.reason)
+        \(location.content)
+        \(highlight)
+        """
+    }
+
+	var descriptions = templateError.stackTrace.reduce(into: []) { $0.append(describe(token: $1)) }
+    let description = templateError.token.map(describe(token:)) ?? templateError.reason
+    descriptions.append(description)
+    return descriptions.joined(separator: "\n")
+  }
+}

Sources/Stencil/Expression.swift

@@ -1,18 +1,27 @@
-protocol Expression: CustomStringConvertible {
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+public protocol Expression: CustomStringConvertible, Resolvable {
   func evaluate(context: Context) throws -> Bool
 }
 
+extension Expression {
+  func resolve(_ context: Context) throws -> Any? {
+    try "\(evaluate(context: context))"
+  }
+}
 
 protocol InfixOperator: Expression {
   init(lhs: Expression, rhs: Expression)
 }
 
-
 protocol PrefixOperator: Expression {
   init(expression: Expression)
 }
 
-
 final class StaticExpression: Expression, CustomStringConvertible {
   let value: Bool
 
@@ -21,15 +30,14 @@ final class StaticExpression: Expression, CustomStringConvertible {
   }
 
   func evaluate(context: Context) throws -> Bool {
-    return value
+    value
   }
 
   var description: String {
-    return "\(value)"
+    "\(value)"
   }
 }
 
-
 final class VariableExpression: Expression, CustomStringConvertible {
   let variable: Resolvable
 
@@ -38,17 +46,21 @@ final class VariableExpression: Expression, CustomStringConvertible {
   }
 
   var description: String {
-    return "(variable: \(variable))"
+    "(variable: \(variable))"
+  }
+
+  func resolve(_ context: Context) throws -> Any? {
+    try variable.resolve(context)
   }
 
   /// Resolves a variable in the given context as boolean
-  func resolve(context: Context, variable: Resolvable) throws -> Bool {
+  func evaluate(context: Context) throws -> Bool {
     let result = try variable.resolve(context)
     var truthy = false
 
     if let result = result as? [Any] {
       truthy = !result.isEmpty
-    } else if let result = result as? [String:Any] {
+    } else if let result = result as? [String: Any] {
       truthy = !result.isEmpty
     } else if let result = result as? Bool {
       truthy = result
@@ -62,13 +74,8 @@ final class VariableExpression: Expression, CustomStringConvertible {
 
     return truthy
   }
-
-  func evaluate(context: Context) throws -> Bool {
-    return try resolve(context: context, variable: variable)
-  }
 }
 
-
 final class NotExpression: Expression, PrefixOperator, CustomStringConvertible {
   let expression: Expression
 
@@ -77,44 +84,47 @@ final class NotExpression: Expression, PrefixOperator, CustomStringConvertible {
   }
 
   var description: String {
-    return "not \(expression)"
+    "not \(expression)"
   }
 
   func evaluate(context: Context) throws -> Bool {
-    return try !expression.evaluate(context: context)
+    try !expression.evaluate(context: context)
   }
 }
 
 final class InExpression: Expression, InfixOperator, CustomStringConvertible {
   let lhs: Expression
   let rhs: Expression
-  
+
   init(lhs: Expression, rhs: Expression) {
     self.lhs = lhs
     self.rhs = rhs
   }
-  
+
   var description: String {
-    return "(\(lhs) in \(rhs))"
+    "(\(lhs) in \(rhs))"
   }
-  
+
   func evaluate(context: Context) throws -> Bool {
     if let lhs = lhs as? VariableExpression, let rhs = rhs as? VariableExpression {
       let lhsValue = try lhs.variable.resolve(context)
       let rhsValue = try rhs.variable.resolve(context)
-      
+
       if let lhs = lhsValue as? AnyHashable, let rhs = rhsValue as? [AnyHashable] {
         return rhs.contains(lhs)
+      } else if let lhs = lhsValue as? Int, let rhs = rhsValue as? CountableClosedRange<Int> {
+        return rhs.contains(lhs)
+      } else if let lhs = lhsValue as? Int, let rhs = rhsValue as? CountableRange<Int> {
+        return rhs.contains(lhs)
       } else if let lhs = lhsValue as? String, let rhs = rhsValue as? String {
         return rhs.contains(lhs)
       } else if lhsValue == nil && rhsValue == nil {
         return true
       }
     }
-    
+
     return false
   }
-  
 }
 
 final class OrExpression: Expression, InfixOperator, CustomStringConvertible {
@@ -127,7 +137,7 @@ final class OrExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 
   var description: String {
-    return "(\(lhs) or \(rhs))"
+    "(\(lhs) or \(rhs))"
   }
 
   func evaluate(context: Context) throws -> Bool {
@@ -140,7 +150,6 @@ final class OrExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 }
 
-
 final class AndExpression: Expression, InfixOperator, CustomStringConvertible {
   let lhs: Expression
   let rhs: Expression
@@ -151,7 +160,7 @@ final class AndExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 
   var description: String {
-    return "(\(lhs) and \(rhs))"
+    "(\(lhs) and \(rhs))"
   }
 
   func evaluate(context: Context) throws -> Bool {
@@ -164,7 +173,6 @@ final class AndExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 }
 
-
 class EqualityExpression: Expression, InfixOperator, CustomStringConvertible {
   let lhs: Expression
   let rhs: Expression
@@ -175,7 +183,7 @@ class EqualityExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 
   var description: String {
-    return "(\(lhs) == \(rhs))"
+    "(\(lhs) == \(rhs))"
   }
 
   func evaluate(context: Context) throws -> Bool {
@@ -200,7 +208,6 @@ class EqualityExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 }
 
-
 class NumericExpression: Expression, InfixOperator, CustomStringConvertible {
   let lhs: Expression
   let rhs: Expression
@@ -211,7 +218,7 @@ class NumericExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 
   var description: String {
-    return "(\(lhs) \(op) \(rhs))"
+    "(\(lhs) \(symbol) \(rhs))"
   }
 
   func evaluate(context: Context) throws -> Bool {
@@ -229,103 +236,98 @@ class NumericExpression: Expression, InfixOperator, CustomStringConvertible {
     return false
   }
 
-  var op: String {
+  var symbol: String {
-    return ""
+    ""
   }
 
   func compare(lhs: Number, rhs: Number) -> Bool {
-    return false
+    false
   }
 }
 
-
 class MoreThanExpression: NumericExpression {
-  override var op: String {
+  override var symbol: String {
-    return ">"
+    ">"
   }
 
   override func compare(lhs: Number, rhs: Number) -> Bool {
-    return lhs > rhs
+    lhs > rhs
   }
 }
 
-
 class MoreThanEqualExpression: NumericExpression {
-  override var op: String {
+  override var symbol: String {
-    return ">="
+    ">="
   }
 
   override func compare(lhs: Number, rhs: Number) -> Bool {
-    return lhs >= rhs
+    lhs >= rhs
   }
 }
 
-
 class LessThanExpression: NumericExpression {
-  override var op: String {
+  override var symbol: String {
-    return "<"
+    "<"
   }
 
   override func compare(lhs: Number, rhs: Number) -> Bool {
-    return lhs < rhs
+    lhs < rhs
   }
 }
 
-
 class LessThanEqualExpression: NumericExpression {
-  override var op: String {
+  override var symbol: String {
-    return "<="
+    "<="
   }
 
   override func compare(lhs: Number, rhs: Number) -> Bool {
-    return lhs <= rhs
+    lhs <= rhs
   }
 }
 
-
 class InequalityExpression: EqualityExpression {
   override var description: String {
-    return "(\(lhs) != \(rhs))"
+    "(\(lhs) != \(rhs))"
   }
 
   override func evaluate(context: Context) throws -> Bool {
-    return try !super.evaluate(context: context)
+    try !super.evaluate(context: context)
   }
 }
 
-
+// swiftlint:disable:next cyclomatic_complexity
 func toNumber(value: Any) -> Number? {
-    if let value = value as? Float {
+  if let value = value as? Float {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? Double {
+  } else if let value = value as? Double {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? UInt {
+  } else if let value = value as? UInt {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? Int {
+  } else if let value = value as? Int {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? Int8 {
+  } else if let value = value as? Int8 {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? Int16 {
+  } else if let value = value as? Int16 {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? Int32 {
+  } else if let value = value as? Int32 {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? Int64 {
+  } else if let value = value as? Int64 {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? UInt8 {
+  } else if let value = value as? UInt8 {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? UInt16 {
+  } else if let value = value as? UInt16 {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? UInt32 {
+  } else if let value = value as? UInt32 {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? UInt64 {
+  } else if let value = value as? UInt64 {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? Number {
+  } else if let value = value as? Number {
-        return value
+    return value
-    } else if let value = value as? Float64 {
+  } else if let value = value as? Float64 {
-        return Number(value)
+    return Number(value)
-    } else if let value = value as? Float32 {
+  } else if let value = value as? Float32 {
-        return Number(value)
+    return Number(value)
-    }
+  }
 
-    return nil
+  return nil
 }

Sources/Stencil/Extension.swift

@@ -1,9 +1,17 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+/// Container for registered tags and filters
 open class Extension {
   typealias TagParser = (TokenParser, Token) throws -> NodeType
-  var tags = [String: TagParser]()
 
+  var tags = [String: TagParser]()
   var filters = [String: Filter]()
 
+  /// Simple initializer
   public init() {
   }
 
@@ -14,9 +22,19 @@ open class Extension {
 
   /// Registers a simple template tag with a name and a handler
   public func registerSimpleTag(_ name: String, handler: @escaping (Context) throws -> String) {
-    registerTag(name, parser: { parser, token in
+    registerTag(name) { _, token in
-      return SimpleNode(handler: handler)
+      SimpleNode(token: token, handler: handler)
-    })
+    }
+  }
+
+  /// Registers boolean filter with it's negative counterpart
+  public func registerFilter(name: String, negativeFilterName: String, filter: @escaping (Any?) throws -> Bool?) {
+    // swiftlint:disable:previous discouraged_optional_boolean
+    filters[name] = .simple(filter)
+    filters[negativeFilterName] = .simple { value in
+      guard let result = try filter(value) else { return nil }
+      return !result
+    }
   }
 
   /// Registers a template filter with the given name
@@ -26,11 +44,15 @@ open class Extension {
 
   /// Registers a template filter with the given name
   public func registerFilter(_ name: String, filter: @escaping (Any?, [Any?]) throws -> Any?) {
+    filters[name] = .arguments { value, args, _ in try filter(value, args) }
+  }
+
+  /// Registers a template filter with the given name
+  public func registerFilter(_ name: String, filter: @escaping (Any?, [Any?], Context) throws -> Any?) {
     filters[name] = .arguments(filter)
   }
 }
 
-
 class DefaultExtension: Extension {
   override init() {
     super.init()
@@ -40,11 +62,13 @@ class DefaultExtension: Extension {
 
   fileprivate func registerDefaultTags() {
     registerTag("for", parser: ForNode.parse)
+    registerTag("break", parser: LoopTerminationNode.parse)
+    registerTag("continue", parser: LoopTerminationNode.parse)
     registerTag("if", parser: IfNode.parse)
     registerTag("ifnot", parser: IfNode.parse_ifnot)
-#if !os(Linux)
+    #if !os(Linux)
-    registerTag("now", parser: NowNode.parse)
+      registerTag("now", parser: NowNode.parse)
-#endif
+    #endif
     registerTag("include", parser: IncludeNode.parse)
     registerTag("extends", parser: ExtendsNode.parse)
     registerTag("block", parser: BlockNode.parse)
@@ -57,28 +81,29 @@ class DefaultExtension: Extension {
     registerFilter("uppercase", filter: uppercase)
     registerFilter("lowercase", filter: lowercase)
     registerFilter("join", filter: joinFilter)
+    registerFilter("split", filter: splitFilter)
+    registerFilter("indent", filter: indentFilter)
+    registerFilter("filter", filter: filterFilter)
   }
 }
 
-
 protocol FilterType {
-  func invoke(value: Any?, arguments: [Any?]) throws -> Any?
+  func invoke(value: Any?, arguments: [Any?], context: Context) throws -> Any?
 }
 
 enum Filter: FilterType {
   case simple(((Any?) throws -> Any?))
-  case arguments(((Any?, [Any?]) throws -> Any?))
+  case arguments(((Any?, [Any?], Context) throws -> Any?))
 
-  func invoke(value: Any?, arguments: [Any?]) throws -> Any? {
+  func invoke(value: Any?, arguments: [Any?], context: Context) throws -> Any? {
     switch self {
     case let .simple(filter):
       if !arguments.isEmpty {
-        throw TemplateSyntaxError("cannot invoke filter with an argument")
+        throw TemplateSyntaxError("Can't invoke filter with an argument")
       }
-
       return try filter(value)
     case let .arguments(filter):
-      return try filter(value, arguments)
+      return try filter(value, arguments, context)
     }
   }
 }

Sources/Stencil/FilterTag.swift

@@ -1,9 +1,16 @@
-class FilterNode : NodeType {
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+class FilterNode: NodeType {
   let resolvable: Resolvable
   let nodes: [NodeType]
+  let token: Token?
 
   class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
-    let bits = token.components()
+    let bits = token.components
 
     guard bits.count == 2 else {
       throw TemplateSyntaxError("'filter' tag takes one argument, the filter expression")
@@ -15,21 +22,21 @@ class FilterNode : NodeType {
       throw TemplateSyntaxError("`endfilter` was not found.")
     }
 
-    let resolvable = try parser.compileFilter("filter_value|\(bits[1])")
+    let resolvable = try parser.compileFilter("filter_value|\(bits[1])", containedIn: token)
-    return FilterNode(nodes: blocks, resolvable: resolvable)
+    return FilterNode(nodes: blocks, resolvable: resolvable, token: token)
   }
 
-  init(nodes: [NodeType], resolvable: Resolvable) {
+  init(nodes: [NodeType], resolvable: Resolvable, token: Token) {
     self.nodes = nodes
     self.resolvable = resolvable
+    self.token = token
   }
 
   func render(_ context: Context) throws -> String {
     let value = try renderNodes(nodes, context)
 
     return try context.push(dictionary: ["filter_value": value]) {
-      return try VariableNode(variable: resolvable).render(context)
+      try VariableNode(variable: resolvable, token: token).render(context)
     }
   }
 }
-

Sources/Stencil/Filters.swift

@@ -0,0 +1,139 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+func capitalise(_ value: Any?) -> Any? {
+  if let array = value as? [Any?] {
+    return array.map { stringify($0).capitalized }
+  } else {
+    return stringify(value).capitalized
+  }
+}
+
+func uppercase(_ value: Any?) -> Any? {
+  if let array = value as? [Any?] {
+    return array.map { stringify($0).uppercased() }
+  } else {
+    return stringify(value).uppercased()
+  }
+}
+
+func lowercase(_ value: Any?) -> Any? {
+  if let array = value as? [Any?] {
+    return array.map { stringify($0).lowercased() }
+  } else {
+    return stringify(value).lowercased()
+  }
+}
+
+func defaultFilter(value: Any?, arguments: [Any?]) -> Any? {
+  // value can be optional wrapping nil, so this way we check for underlying value
+  if let value = value, String(describing: value) != "nil" {
+    return value
+  }
+
+  for argument in arguments {
+    if let argument = argument {
+      return argument
+    }
+  }
+
+  return nil
+}
+
+func joinFilter(value: Any?, arguments: [Any?]) throws -> Any? {
+  guard arguments.count < 2 else {
+    throw TemplateSyntaxError("'join' filter takes at most one argument")
+  }
+
+  let separator = stringify(arguments.first ?? "")
+
+  if let value = value as? [Any] {
+    return value
+      .map(stringify)
+      .joined(separator: separator)
+  }
+
+  return value
+}
+
+func splitFilter(value: Any?, arguments: [Any?]) throws -> Any? {
+  guard arguments.count < 2 else {
+    throw TemplateSyntaxError("'split' filter takes at most one argument")
+  }
+
+  let separator = stringify(arguments.first ?? " ")
+  if let value = value as? String {
+    return value.components(separatedBy: separator)
+  }
+
+  return value
+}
+
+func indentFilter(value: Any?, arguments: [Any?]) throws -> Any? {
+  guard arguments.count <= 3 else {
+    throw TemplateSyntaxError("'indent' filter can take at most 3 arguments")
+  }
+
+  var indentWidth = 4
+  if !arguments.isEmpty {
+    guard let value = arguments[0] as? Int else {
+      throw TemplateSyntaxError(
+        """
+        'indent' filter width argument must be an Integer (\(String(describing: arguments[0])))
+        """
+      )
+    }
+    indentWidth = value
+  }
+
+  var indentationChar = " "
+  if arguments.count > 1 {
+    guard let value = arguments[1] as? String else {
+      throw TemplateSyntaxError(
+        """
+        'indent' filter indentation argument must be a String (\(String(describing: arguments[1]))
+        """
+      )
+    }
+    indentationChar = value
+  }
+
+  var indentFirst = false
+  if arguments.count > 2 {
+    guard let value = arguments[2] as? Bool else {
+      throw TemplateSyntaxError("'indent' filter indentFirst argument must be a Bool")
+    }
+    indentFirst = value
+  }
+
+  let indentation = [String](repeating: indentationChar, count: indentWidth).joined()
+  return indent(stringify(value), indentation: indentation, indentFirst: indentFirst)
+}
+
+func indent(_ content: String, indentation: String, indentFirst: Bool) -> String {
+  guard !indentation.isEmpty else { return content }
+
+  var lines = content.components(separatedBy: .newlines)
+  let firstLine = (indentFirst ? indentation : "") + lines.removeFirst()
+  let result = lines.reduce(into: [firstLine]) { result, line in
+    result.append(line.isEmpty ? "" : "\(indentation)\(line)")
+  }
+  return result.joined(separator: "\n")
+}
+
+func filterFilter(value: Any?, arguments: [Any?], context: Context) throws -> Any? {
+  guard let value = value else { return nil }
+  guard arguments.count == 1 else {
+    throw TemplateSyntaxError("'filter' filter takes one argument")
+  }
+
+  let attribute = stringify(arguments[0])
+
+  let expr = try context.environment.compileFilter("$0|\(attribute)")
+  return try context.push(dictionary: ["$0": value]) {
+    try expr.resolve(context)
+  }
+}

Sources/Stencil/ForTag.swift

@@ -0,0 +1,280 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import Foundation
+
+class ForNode: NodeType {
+  let resolvable: Resolvable
+  let loopVariables: [String]
+  let nodes: [NodeType]
+  let emptyNodes: [NodeType]
+  let `where`: Expression?
+  let label: String?
+  let token: Token?
+
+  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
+    var components = token.components
+
+    var label: String?
+    if components.first?.hasSuffix(":") == true {
+      label = String(components.removeFirst().dropLast())
+    }
+
+    func hasToken(_ token: String, at index: Int) -> Bool {
+      components.count > (index + 1) && components[index] == token
+    }
+
+    func endsOrHasToken(_ token: String, at index: Int) -> Bool {
+      components.count == index || hasToken(token, at: index)
+    }
+
+    guard hasToken("in", at: 2) && endsOrHasToken("where", at: 4) else {
+      throw TemplateSyntaxError("'for' statements should use the syntax: `for <x> in <y> [where <condition>]`.")
+    }
+
+    let loopVariables = components[1]
+      .split(separator: ",")
+      .map(String.init)
+      .map { $0.trim(character: " ") }
+
+    let resolvable = try parser.compileResolvable(components[3], containedIn: token)
+
+    let `where` = hasToken("where", at: 4)
+      ? try parser.compileExpression(components: Array(components.suffix(from: 5)), token: token)
+      : nil
+
+    let forNodes = try parser.parse(until(["endfor", "empty"]))
+
+    guard let token = parser.nextToken() else {
+      throw TemplateSyntaxError("`endfor` was not found.")
+    }
+
+    var emptyNodes = [NodeType]()
+    if token.contents == "empty" {
+      emptyNodes = try parser.parse(until(["endfor"]))
+      _ = parser.nextToken()
+    }
+
+    return ForNode(
+      resolvable: resolvable,
+      loopVariables: loopVariables,
+      nodes: forNodes,
+      emptyNodes: emptyNodes,
+      where: `where`,
+      label: label,
+      token: token
+    )
+  }
+
+  init(
+    resolvable: Resolvable,
+    loopVariables: [String],
+    nodes: [NodeType],
+    emptyNodes: [NodeType],
+    where: Expression? = nil,
+    label: String? = nil,
+    token: Token? = nil
+  ) {
+    self.resolvable = resolvable
+    self.loopVariables = loopVariables
+    self.nodes = nodes
+    self.emptyNodes = emptyNodes
+    self.where = `where`
+    self.label = label
+    self.token = token
+  }
+
+  func render(_ context: Context) throws -> String {
+    var values = try resolve(context)
+
+    if let `where` = self.where {
+      values = try values.filter { item -> Bool in
+        try push(value: item, context: context) {
+          try `where`.evaluate(context: context)
+        }
+      }
+    }
+
+    if !values.isEmpty {
+      let count = values.count
+      var result = ""
+
+      // collect parent loop contexts
+      let parentLoopContexts = (context["forloop"] as? [String: Any])?
+        .filter { ($1 as? [String: Any])?["label"] != nil } ?? [:]
+
+      for (index, item) in zip(0..., values) {
+        var forContext: [String: Any] = [
+          "first": index == 0,
+          "last": index == (count - 1),
+          "counter": index + 1,
+          "counter0": index,
+          "length": count
+        ]
+        if let label = label {
+          forContext["label"] = label
+          forContext[label] = forContext
+        }
+        forContext.merge(parentLoopContexts) { lhs, _ in lhs }
+
+        var shouldBreak = false
+        result += try context.push(dictionary: ["forloop": forContext]) {
+          defer {
+            // if outer loop should be continued we should break from current loop
+            if let shouldContinueLabel = context[LoopTerminationNode.continueContextKey] as? String {
+              shouldBreak = shouldContinueLabel != label || label == nil
+            } else {
+              shouldBreak = context[LoopTerminationNode.breakContextKey] != nil
+            }
+          }
+          return try push(value: item, context: context) {
+            try renderNodes(nodes, context)
+          }
+        }
+
+        if shouldBreak {
+          break
+        }
+      }
+
+      return result
+    } else {
+      return try context.push {
+        try renderNodes(emptyNodes, context)
+      }
+    }
+  }
+
+  private func push<Result>(value: Any, context: Context, closure: () throws -> (Result)) throws -> Result {
+    if loopVariables.isEmpty {
+      return try context.push {
+        try closure()
+      }
+    }
+
+    let valueMirror = Mirror(reflecting: value)
+    if case .tuple? = valueMirror.displayStyle {
+      if loopVariables.count > Int(valueMirror.children.count) {
+        throw TemplateSyntaxError("Tuple '\(value)' has less values than loop variables")
+      }
+      var variablesContext = [String: Any]()
+      valueMirror.children.prefix(loopVariables.count).enumerated().forEach { offset, element in
+        if loopVariables[offset] != "_" {
+          variablesContext[loopVariables[offset]] = element.value
+        }
+      }
+
+      return try context.push(dictionary: variablesContext) {
+        try closure()
+      }
+    }
+
+    return try context.push(dictionary: [loopVariables.first ?? "": value]) {
+      try closure()
+    }
+  }
+
+  private func resolve(_ context: Context) throws -> [Any] {
+    let resolved = try resolvable.resolve(context)
+
+    var values: [Any]
+    if let dictionary = resolved as? [String: Any], !dictionary.isEmpty {
+      values = dictionary.sorted { $0.key < $1.key }
+    } else if let array = resolved as? [Any] {
+      values = array
+    } else if let range = resolved as? CountableClosedRange<Int> {
+      values = Array(range)
+    } else if let range = resolved as? CountableRange<Int> {
+      values = Array(range)
+    } else if let resolved = resolved {
+      let mirror = Mirror(reflecting: resolved)
+      switch mirror.displayStyle {
+      case .struct, .tuple:
+        values = Array(mirror.children)
+      case .class:
+        var children = Array(mirror.children)
+        var currentMirror: Mirror? = mirror
+        while let superclassMirror = currentMirror?.superclassMirror {
+          children.append(contentsOf: superclassMirror.children)
+          currentMirror = superclassMirror
+        }
+        values = Array(children)
+      default:
+        values = []
+      }
+    } else {
+      values = []
+    }
+
+    return values
+  }
+}
+
+struct LoopTerminationNode: NodeType {
+  static let breakContextKey = "_internal_forloop_break"
+  static let continueContextKey = "_internal_forloop_continue"
+
+  let name: String
+  let label: String?
+  let token: Token?
+
+  var contextKey: String {
+    "_internal_forloop_\(name)"
+  }
+
+  private init(name: String, label: String? = nil, token: Token? = nil) {
+    self.name = name
+    self.label = label
+    self.token = token
+  }
+
+  static func parse(_ parser: TokenParser, token: Token) throws -> LoopTerminationNode {
+    let components = token.components
+
+    guard components.count <= 2 else {
+      throw TemplateSyntaxError("'\(token.contents)' can accept only one parameter")
+    }
+    guard parser.hasOpenedForTag() else {
+      throw TemplateSyntaxError("'\(token.contents)' can be used only inside loop body")
+    }
+
+    return LoopTerminationNode(name: components[0], label: components.count == 2 ? components[1] : nil, token: token)
+  }
+
+  func render(_ context: Context) throws -> String {
+    let offset = zip(0..., context.dictionaries).reversed().first { _, dictionary in
+      guard let forContext = dictionary["forloop"] as? [String: Any],
+        dictionary["forloop"] != nil else { return false }
+
+      if let label = label {
+        return label == forContext["label"] as? String
+      } else {
+        return true
+      }
+    }?.0
+
+    if let offset = offset {
+      context.dictionaries[offset][contextKey] = label ?? true
+    } else if let label = label {
+      throw TemplateSyntaxError("No loop labeled '\(label)' is currently running")
+    } else {
+      throw TemplateSyntaxError("No loop is currently running")
+    }
+
+    return ""
+  }
+}
+
+private extension TokenParser {
+  func hasOpenedForTag() -> Bool {
+    var openForCount = 0
+    for parsedToken in parsedTokens.reversed() where parsedToken.kind == .block {
+      if parsedToken.components.first == "endfor" { openForCount -= 1 }
+      if parsedToken.components.first == "for" { openForCount += 1 }
+    }
+    return openForCount > 0
+  }
+}

Sources/Stencil/IfTag.swift

@@ -0,0 +1,319 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+enum Operator {
+  case infix(String, Int, InfixOperator.Type)
+  case prefix(String, Int, PrefixOperator.Type)
+
+  var name: String {
+    switch self {
+    case .infix(let name, _, _):
+      return name
+    case .prefix(let name, _, _):
+      return name
+    }
+  }
+
+  static let all: [Operator] = [
+    .infix("in", 5, InExpression.self),
+    .infix("or", 6, OrExpression.self),
+    .infix("and", 7, AndExpression.self),
+    .prefix("not", 8, NotExpression.self),
+    .infix("==", 10, EqualityExpression.self),
+    .infix("!=", 10, InequalityExpression.self),
+    .infix(">", 10, MoreThanExpression.self),
+    .infix(">=", 10, MoreThanEqualExpression.self),
+    .infix("<", 10, LessThanExpression.self),
+    .infix("<=", 10, LessThanEqualExpression.self)
+  ]
+}
+
+func findOperator(name: String) -> Operator? {
+  for `operator` in Operator.all where `operator`.name == name {
+    return `operator`
+  }
+
+  return nil
+}
+
+indirect enum IfToken {
+  case infix(name: String, bindingPower: Int, operatorType: InfixOperator.Type)
+  case prefix(name: String, bindingPower: Int, operatorType: PrefixOperator.Type)
+  case variable(Resolvable)
+  case subExpression(Expression)
+  case end
+
+  var bindingPower: Int {
+    switch self {
+    case .infix(_, let bindingPower, _):
+      return bindingPower
+    case .prefix(_, let bindingPower, _):
+      return bindingPower
+    case .variable:
+      return 0
+    case .subExpression:
+      return 0
+    case .end:
+      return 0
+    }
+  }
+
+  func nullDenotation(parser: IfExpressionParser) throws -> Expression {
+    switch self {
+    case .infix(let name, _, _):
+      throw TemplateSyntaxError("'if' expression error: infix operator '\(name)' doesn't have a left hand side")
+    case .prefix(_, let bindingPower, let operatorType):
+      let expression = try parser.expression(bindingPower: bindingPower)
+      return operatorType.init(expression: expression)
+    case .variable(let variable):
+      return VariableExpression(variable: variable)
+    case .subExpression(let expression):
+      return expression
+    case .end:
+      throw TemplateSyntaxError("'if' expression error: end")
+    }
+  }
+
+  func leftDenotation(left: Expression, parser: IfExpressionParser) throws -> Expression {
+    switch self {
+    case .infix(_, let bindingPower, let operatorType):
+      let right = try parser.expression(bindingPower: bindingPower)
+      return operatorType.init(lhs: left, rhs: right)
+    case .prefix(let name, _, _):
+      throw TemplateSyntaxError("'if' expression error: prefix operator '\(name)' was called with a left hand side")
+    case .variable(let variable):
+      throw TemplateSyntaxError("'if' expression error: variable '\(variable)' was called with a left hand side")
+    case .subExpression:
+      throw TemplateSyntaxError("'if' expression error: sub expression was called with a left hand side")
+    case .end:
+      throw TemplateSyntaxError("'if' expression error: end")
+    }
+  }
+
+  var isEnd: Bool {
+    switch self {
+    case .end:
+      return true
+    default:
+      return false
+    }
+  }
+}
+
+final class IfExpressionParser {
+  let tokens: [IfToken]
+  var position: Int = 0
+
+  private init(tokens: [IfToken]) {
+    self.tokens = tokens
+  }
+
+  static func parser(components: [String], environment: Environment, token: Token) throws -> IfExpressionParser {
+    try IfExpressionParser(components: ArraySlice(components), environment: environment, token: token)
+  }
+
+  private init(components: ArraySlice<String>, environment: Environment, token: Token) throws {
+    var parsedComponents = Set<Int>()
+    var bracketsBalance = 0
+    self.tokens = try zip(components.indices, components).compactMap { index, component in
+      guard !parsedComponents.contains(index) else { return nil }
+
+      if component == "(" {
+        bracketsBalance += 1
+        let (expression, parsedCount) = try Self.subExpression(
+          from: components.suffix(from: index + 1),
+          environment: environment,
+          token: token
+        )
+        parsedComponents.formUnion(Set(index...(index + parsedCount)))
+        return .subExpression(expression)
+      } else if component == ")" {
+        bracketsBalance -= 1
+        if bracketsBalance < 0 {
+          throw TemplateSyntaxError("'if' expression error: missing opening bracket")
+        }
+        parsedComponents.insert(index)
+        return nil
+      } else {
+        parsedComponents.insert(index)
+        if let `operator` = findOperator(name: component) {
+          switch `operator` {
+          case .infix(let name, let bindingPower, let operatorType):
+            return .infix(name: name, bindingPower: bindingPower, operatorType: operatorType)
+          case .prefix(let name, let bindingPower, let operatorType):
+            return .prefix(name: name, bindingPower: bindingPower, operatorType: operatorType)
+          }
+        }
+        return .variable(try environment.compileResolvable(component, containedIn: token))
+      }
+    }
+  }
+
+  private static func subExpression(
+    from components: ArraySlice<String>,
+    environment: Environment,
+    token: Token
+  ) throws -> (Expression, Int) {
+    var bracketsBalance = 1
+    let subComponents = components.prefix { component in
+      if component == "(" {
+        bracketsBalance += 1
+      } else if component == ")" {
+        bracketsBalance -= 1
+      }
+      return bracketsBalance != 0
+    }
+    if bracketsBalance > 0 {
+      throw TemplateSyntaxError("'if' expression error: missing closing bracket")
+    }
+
+    let expressionParser = try IfExpressionParser(components: subComponents, environment: environment, token: token)
+    let expression = try expressionParser.parse()
+    return (expression, subComponents.count)
+  }
+
+  var currentToken: IfToken {
+    if tokens.count > position {
+      return tokens[position]
+    }
+
+    return .end
+  }
+
+  var nextToken: IfToken {
+    position += 1
+    return currentToken
+  }
+
+  func parse() throws -> Expression {
+    let expression = try self.expression()
+
+    if !currentToken.isEnd {
+      throw TemplateSyntaxError("'if' expression error: dangling token")
+    }
+
+    return expression
+  }
+
+  func expression(bindingPower: Int = 0) throws -> Expression {
+    var token = currentToken
+    position += 1
+
+    var left = try token.nullDenotation(parser: self)
+
+    while bindingPower < currentToken.bindingPower {
+      token = currentToken
+      position += 1
+      left = try token.leftDenotation(left: left, parser: self)
+    }
+
+    return left
+  }
+}
+
+/// Represents an if condition and the associated nodes when the condition
+/// evaluates
+final class IfCondition {
+  let expression: Expression?
+  let nodes: [NodeType]
+
+  init(expression: Expression?, nodes: [NodeType]) {
+    self.expression = expression
+    self.nodes = nodes
+  }
+
+  func render(_ context: Context) throws -> String {
+    try context.push {
+      try renderNodes(nodes, context)
+    }
+  }
+}
+
+class IfNode: NodeType {
+  let conditions: [IfCondition]
+  let token: Token?
+
+  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
+    var components = token.components
+    components.removeFirst()
+
+    let expression = try parser.compileExpression(components: components, token: token)
+    let nodes = try parser.parse(until(["endif", "elif", "else"]))
+    var conditions: [IfCondition] = [
+      IfCondition(expression: expression, nodes: nodes)
+    ]
+
+    var nextToken = parser.nextToken()
+    while let current = nextToken, current.contents.hasPrefix("elif") {
+      var components = current.components
+      components.removeFirst()
+      let expression = try parser.compileExpression(components: components, token: current)
+
+      let nodes = try parser.parse(until(["endif", "elif", "else"]))
+      nextToken = parser.nextToken()
+      conditions.append(IfCondition(expression: expression, nodes: nodes))
+    }
+
+    if let current = nextToken, current.contents == "else" {
+      conditions.append(IfCondition(expression: nil, nodes: try parser.parse(until(["endif"]))))
+      nextToken = parser.nextToken()
+    }
+
+    guard let current = nextToken, current.contents == "endif" else {
+      throw TemplateSyntaxError("`endif` was not found.")
+    }
+
+    return IfNode(conditions: conditions, token: token)
+  }
+
+  class func parse_ifnot(_ parser: TokenParser, token: Token) throws -> NodeType {
+    var components = token.components
+    guard components.count == 2 else {
+      throw TemplateSyntaxError("'ifnot' statements should use the following syntax 'ifnot condition'.")
+    }
+    components.removeFirst()
+    var trueNodes = [NodeType]()
+    var falseNodes = [NodeType]()
+
+    let expression = try parser.compileExpression(components: components, token: token)
+    falseNodes = try parser.parse(until(["endif", "else"]))
+
+    guard let token = parser.nextToken() else {
+      throw TemplateSyntaxError("`endif` was not found.")
+    }
+
+    if token.contents == "else" {
+      trueNodes = try parser.parse(until(["endif"]))
+      _ = parser.nextToken()
+    }
+
+    return IfNode(conditions: [
+      IfCondition(expression: expression, nodes: trueNodes),
+      IfCondition(expression: nil, nodes: falseNodes)
+    ], token: token)
+  }
+
+  init(conditions: [IfCondition], token: Token? = nil) {
+    self.conditions = conditions
+    self.token = token
+  }
+
+  func render(_ context: Context) throws -> String {
+    for condition in conditions {
+      if let expression = condition.expression {
+        let truthy = try expression.evaluate(context: context)
+
+        if truthy {
+          return try condition.render(context)
+        }
+      } else {
+        return try condition.render(context)
+      }
+    }
+
+    return ""
+  }
+}

Sources/Stencil/Include.swift

@@ -0,0 +1,56 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import PathKit
+
+class IncludeNode: NodeType {
+  let templateName: Variable
+  let includeContext: String?
+  let token: Token?
+
+  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
+    let bits = token.components
+
+    guard bits.count == 2 || bits.count == 3 else {
+      throw TemplateSyntaxError(
+        """
+        'include' tag requires one argument, the template file to be included. \
+        A second optional argument can be used to specify the context that will \
+        be passed to the included file
+        """
+      )
+    }
+
+    return IncludeNode(templateName: Variable(bits[1]), includeContext: bits.count == 3 ? bits[2] : nil, token: token)
+  }
+
+  init(templateName: Variable, includeContext: String? = nil, token: Token) {
+    self.templateName = templateName
+    self.includeContext = includeContext
+    self.token = token
+  }
+
+  func render(_ context: Context) throws -> String {
+    guard let templateName = try self.templateName.resolve(context) as? String else {
+      throw TemplateSyntaxError("'\(self.templateName)' could not be resolved as a string")
+    }
+
+    let template = try context.environment.loadTemplate(name: templateName)
+
+    do {
+      let subContext = includeContext.flatMap { context[$0] as? [String: Any] } ?? [:]
+      return try context.push(dictionary: subContext) {
+        try template.render(context)
+      }
+    } catch {
+      if let error = error as? TemplateSyntaxError {
+        throw TemplateSyntaxError(reason: error.reason, stackTrace: error.allTokens)
+      } else {
+        throw error
+      }
+    }
+  }
+}

Sources/Stencil/Inheritance.swift

@@ -0,0 +1,164 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+class BlockContext {
+  class var contextKey: String { "block_context" }
+
+  // contains mapping of block names to their nodes and templates where they are defined
+  var blocks: [String: [BlockNode]]
+
+  init(blocks: [String: BlockNode]) {
+    self.blocks = [:]
+    blocks.forEach { self.blocks[$0.key] = [$0.value] }
+  }
+
+  func push(_ block: BlockNode, forKey blockName: String) {
+    if var blocks = blocks[blockName] {
+      blocks.append(block)
+      self.blocks[blockName] = blocks
+    } else {
+      self.blocks[blockName] = [block]
+    }
+  }
+
+  func pop(_ blockName: String) -> BlockNode? {
+    if var blocks = blocks[blockName] {
+      let block = blocks.removeFirst()
+      if blocks.isEmpty {
+        self.blocks.removeValue(forKey: blockName)
+      } else {
+        self.blocks[blockName] = blocks
+      }
+      return block
+    } else {
+      return nil
+    }
+  }
+}
+
+extension Collection {
+  func any(_ closure: (Iterator.Element) -> Bool) -> Iterator.Element? {
+    for element in self where closure(element) {
+      return element
+    }
+
+    return nil
+  }
+}
+
+class ExtendsNode: NodeType {
+  let templateName: Variable
+  let blocks: [String: BlockNode]
+  let token: Token?
+
+  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
+    let bits = token.components
+
+    guard bits.count == 2 else {
+      throw TemplateSyntaxError("'extends' takes one argument, the template file to be extended")
+    }
+
+    let parsedNodes = try parser.parse()
+    guard (parsedNodes.any { $0 is ExtendsNode }) == nil else {
+      throw TemplateSyntaxError("'extends' cannot appear more than once in the same template")
+    }
+
+    let blockNodes = parsedNodes.compactMap { $0 as? BlockNode }
+    let nodes = blockNodes.reduce(into: [String: BlockNode]()) { accumulator, node in
+      accumulator[node.name] = node
+    }
+
+    return ExtendsNode(templateName: Variable(bits[1]), blocks: nodes, token: token)
+  }
+
+  init(templateName: Variable, blocks: [String: BlockNode], token: Token) {
+    self.templateName = templateName
+    self.blocks = blocks
+    self.token = token
+  }
+
+  func render(_ context: Context) throws -> String {
+    guard let templateName = try self.templateName.resolve(context) as? String else {
+      throw TemplateSyntaxError("'\(self.templateName)' could not be resolved as a string")
+    }
+
+    let baseTemplate = try context.environment.loadTemplate(name: templateName)
+
+    let blockContext: BlockContext
+    if let currentBlockContext = context[BlockContext.contextKey] as? BlockContext {
+      blockContext = currentBlockContext
+      for (name, block) in blocks {
+        blockContext.push(block, forKey: name)
+      }
+    } else {
+      blockContext = BlockContext(blocks: blocks)
+    }
+
+    do {
+      // pushes base template and renders it's content
+      // block_context contains all blocks from child templates
+      return try context.push(dictionary: [BlockContext.contextKey: blockContext]) {
+        try baseTemplate.render(context)
+      }
+    } catch {
+      // if error template is already set (see catch in BlockNode)
+      // and it happend in the same template as current template
+      // there is no need to wrap it in another error
+      if let error = error as? TemplateSyntaxError, error.templateName != token?.sourceMap.filename {
+        throw TemplateSyntaxError(reason: error.reason, stackTrace: error.allTokens)
+      } else {
+        throw error
+      }
+    }
+  }
+}
+
+class BlockNode: NodeType {
+  let name: String
+  let nodes: [NodeType]
+  let token: Token?
+
+  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
+    let bits = token.components
+
+    guard bits.count == 2 else {
+      throw TemplateSyntaxError("'block' tag takes one argument, the block name")
+    }
+
+    let blockName = bits[1]
+    let nodes = try parser.parse(until(["endblock"]))
+    _ = parser.nextToken()
+    return BlockNode(name: blockName, nodes: nodes, token: token)
+  }
+
+  init(name: String, nodes: [NodeType], token: Token) {
+    self.name = name
+    self.nodes = nodes
+    self.token = token
+  }
+
+  func render(_ context: Context) throws -> String {
+    if let blockContext = context[BlockContext.contextKey] as? BlockContext, let child = blockContext.pop(name) {
+      let childContext: [String: Any] = [
+        BlockContext.contextKey: blockContext,
+        "block": ["super": try self.render(context)]
+      ]
+
+      // render extension node
+      do {
+        return try context.push(dictionary: childContext) {
+          try child.render(context)
+        }
+      } catch {
+        throw error.withToken(child.token)
+      }
+    }
+
+    let result = try renderNodes(nodes, context)
+    context.cacheBlock(name, content: result)
+    return result
+  }
+}

Sources/Stencil/KeyPath.swift

@@ -0,0 +1,118 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import Foundation
+
+/// A structure used to represent a template variable, and to resolve it in a given context.
+final class KeyPath {
+  private var components = [String]()
+  private var current = ""
+  private var partialComponents = [String]()
+  private var subscriptLevel = 0
+
+  let variable: String
+  let context: Context
+
+  // Split the keypath string and resolve references if possible
+  init(_ variable: String, in context: Context) {
+    self.variable = variable
+    self.context = context
+  }
+
+  func parse() throws -> [String] {
+    defer {
+      components = []
+      current = ""
+      partialComponents = []
+      subscriptLevel = 0
+    }
+
+    for character in variable {
+      switch character {
+      case "." where subscriptLevel == 0:
+        try foundSeparator()
+      case "[":
+        try openBracket()
+      case "]":
+        try closeBracket()
+      default:
+        try addCharacter(character)
+      }
+    }
+    try finish()
+
+    return components
+  }
+
+  private func foundSeparator() throws {
+    if !current.isEmpty {
+      partialComponents.append(current)
+    }
+
+    guard !partialComponents.isEmpty else {
+      throw TemplateSyntaxError("Unexpected '.' in variable '\(variable)'")
+    }
+
+    components += partialComponents
+    current = ""
+    partialComponents = []
+  }
+
+  // when opening the first bracket, we must have a partial component
+  private func openBracket() throws {
+    guard !partialComponents.isEmpty || !current.isEmpty else {
+      throw TemplateSyntaxError("Unexpected '[' in variable '\(variable)'")
+    }
+
+    if subscriptLevel > 0 {
+      current.append("[")
+    } else if !current.isEmpty {
+      partialComponents.append(current)
+      current = ""
+    }
+
+    subscriptLevel += 1
+  }
+
+  // for a closing bracket at root level, try to resolve the reference
+  private func closeBracket() throws {
+    guard subscriptLevel > 0 else {
+      throw TemplateSyntaxError("Unbalanced ']' in variable '\(variable)'")
+    }
+
+    if subscriptLevel > 1 {
+      current.append("]")
+    } else if !current.isEmpty,
+      let value = try Variable(current).resolve(context) {
+      partialComponents.append("\(value)")
+      current = ""
+    } else {
+      throw TemplateSyntaxError("Unable to resolve subscript '\(current)' in variable '\(variable)'")
+    }
+
+    subscriptLevel -= 1
+  }
+
+  private func addCharacter(_ character: Character) throws {
+    guard partialComponents.isEmpty || subscriptLevel > 0 else {
+      throw TemplateSyntaxError("Unexpected character '\(character)' in variable '\(variable)'")
+    }
+
+    current.append(character)
+  }
+
+  private func finish() throws {
+    // check if we have a last piece
+    if !current.isEmpty {
+      partialComponents.append(current)
+    }
+    components += partialComponents
+
+    guard subscriptLevel == 0 else {
+      throw TemplateSyntaxError("Unbalanced subscript brackets in variable '\(variable)'")
+    }
+  }
+}

Sources/Stencil/LazyValueWrapper.swift

@@ -0,0 +1,63 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+/// Used to lazily set context data. Useful for example if you have some data that requires heavy calculations, and may
+/// not be used in every render possiblity.
+public final class LazyValueWrapper {
+  private let closure: (Context) throws -> Any
+  private let context: Context?
+  private var cachedValue: Any?
+
+  /// Create a wrapper that'll use a **reference** to the current context.
+  /// This means when the closure is evaluated, it'll use the **active** context at that moment.
+  ///
+  /// - Parameters:
+  ///   - closure: The closure to lazily evaluate
+  public init(closure: @escaping (Context) throws -> Any) {
+    self.context = nil
+    self.closure = closure
+  }
+
+  /// Create a wrapper that'll create a **copy** of the current context.
+  /// This means when the closure is evaluated, it'll use the context **as it was** when this wrapper was created.
+  ///
+  /// - Parameters:
+  ///   - context: The context to use during evaluation
+  ///   - closure: The closure to lazily evaluate
+  /// - Note: This will use more memory than the other `init` as it needs to keep a copy of the full context around.
+  public init(copying context: Context, closure: @escaping (Context) throws -> Any) {
+    self.context = Context(dictionaries: context.dictionaries, environment: context.environment)
+    self.closure = closure
+  }
+
+  /// Shortcut for creating a lazy wrapper when you don't need access to the Stencil context.
+  ///
+  /// - Parameters:
+  ///   - closure: The closure to lazily evaluate
+  public init(_ closure: @autoclosure @escaping () throws -> Any) {
+    self.context = nil
+    self.closure = { _ in try closure() }
+  }
+}
+
+extension LazyValueWrapper {
+  func value(context: Context) throws -> Any {
+    if let value = cachedValue {
+      return value
+    } else {
+      let value = try closure(self.context ?? context)
+      cachedValue = value
+      return value
+    }
+  }
+}
+
+extension LazyValueWrapper: Resolvable {
+  public func resolve(_ context: Context) throws -> Any? {
+    let value = try self.value(context: context)
+    return try (value as? Resolvable)?.resolve(context) ?? value
+  }
+}

Sources/Stencil/Lexer.swift

@@ -0,0 +1,262 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import Foundation
+
+typealias Line = (content: String, number: UInt, range: Range<String.Index>)
+
+struct Lexer {
+  let templateName: String?
+  let templateString: String
+  let lines: [Line]
+
+  /// The potential token start characters. In a template these appear after a
+  /// `{` character, for example `{{`, `{%`, `{#`, ...
+  private static let tokenChars: [Unicode.Scalar] = ["{", "%", "#"]
+
+  /// The minimum length of a tag
+  private static let tagLength = 2
+
+  /// The token end characters, corresponding to their token start characters.
+  /// For example, a variable token starts with `{{` and ends with `}}`
+  private static let tokenCharMap: [Unicode.Scalar: Unicode.Scalar] = [
+    "{": "}",
+    "%": "%",
+    "#": "#"
+  ]
+
+  /// Characters controlling whitespace trimming behaviour
+  private static let behaviourMap: [Character: WhitespaceBehaviour.Behaviour] = [
+    "+": .keep,
+    "-": .trim
+  ]
+
+  init(templateName: String? = nil, templateString: String) {
+    self.templateName = templateName
+    self.templateString = templateString
+
+    self.lines = zip(1..., templateString.components(separatedBy: .newlines)).compactMap { index, line in
+      guard !line.isEmpty,
+        let range = templateString.range(of: line) else { return nil }
+      return (content: line, number: UInt(index), range)
+    }
+  }
+
+  private func behaviour(string: String, tagLength: Int) -> WhitespaceBehaviour {
+    let leftIndex = string.index(string.startIndex, offsetBy: tagLength, limitedBy: string.endIndex)
+    let rightIndex = string.index(string.endIndex, offsetBy: -(tagLength + 1), limitedBy: string.startIndex)
+
+    return WhitespaceBehaviour(
+      leading: Self.behaviourMap[leftIndex.map { string[$0] } ?? " "] ?? .unspecified,
+      trailing: Self.behaviourMap[rightIndex.map { string[$0] } ?? " "] ?? .unspecified
+    )
+  }
+
+  /// Create a token that will be passed on to the parser, with the given
+  /// content and a range. The content will be tested to see if it's a
+  /// `variable`, a `block` or a `comment`, otherwise it'll default to a simple
+  /// `text` token.
+  ///
+  /// - Parameters:
+  ///   - string: The content string of the token
+  ///   - range: The range within the template content, used for smart
+  ///            error reporting
+  func createToken(string: String, at range: Range<String.Index>) -> Token {
+    func strip(length: (Int, Int) = (Self.tagLength, Self.tagLength)) -> String {
+      guard string.count > (length.0 + length.1) else { return "" }
+      let trimmed = String(string.dropFirst(length.0).dropLast(length.1))
+        .components(separatedBy: "\n")
+        .filter { !$0.isEmpty }
+        .map { $0.trim(character: " ") }
+        .joined(separator: " ")
+      return trimmed
+    }
+
+    if string.hasPrefix("{{") || string.hasPrefix("{%") || string.hasPrefix("{#") {
+      let behaviour = string.hasPrefix("{%") ? behaviour(string: string, tagLength: Self.tagLength) : .unspecified
+      let stripLengths = (
+        Self.tagLength + (behaviour.leading != .unspecified ? 1 : 0),
+        Self.tagLength + (behaviour.trailing != .unspecified ? 1 : 0)
+      )
+
+      let value = strip(length: stripLengths)
+      let range = templateString.range(of: value, range: range) ?? range
+      let location = rangeLocation(range)
+      let sourceMap = SourceMap(filename: templateName, location: location)
+
+      if string.hasPrefix("{{") {
+        return .variable(value: value, at: sourceMap)
+      } else if string.hasPrefix("{%") {
+        return .block(value: strip(length: stripLengths), at: sourceMap, whitespace: behaviour)
+      } else if string.hasPrefix("{#") {
+        return .comment(value: value, at: sourceMap)
+      }
+    }
+
+    let location = rangeLocation(range)
+    let sourceMap = SourceMap(filename: templateName, location: location)
+    return .text(value: string, at: sourceMap)
+  }
+
+  /// Transforms the template into a list of tokens, that will eventually be
+  /// passed on to the parser.
+  ///
+  /// - Returns: The list of tokens (see `createToken(string: at:)`).
+  func tokenize() -> [Token] {
+    var tokens: [Token] = []
+
+    let scanner = Scanner(templateString)
+    while !scanner.isEmpty {
+      if let (char, text) = scanner.scanForTokenStart(Self.tokenChars) {
+        if !text.isEmpty {
+          tokens.append(createToken(string: text, at: scanner.range))
+        }
+
+        guard let end = Self.tokenCharMap[char] else { continue }
+        let result = scanner.scanForTokenEnd(end)
+        tokens.append(createToken(string: result, at: scanner.range))
+      } else {
+        tokens.append(createToken(string: scanner.content, at: scanner.range))
+        scanner.content = ""
+      }
+    }
+
+    return tokens
+  }
+
+  /// Finds the line matching the given range (for a token)
+  ///
+  /// - Parameter range: The range to search for.
+  /// - Returns: The content for that line, the line number and offset within
+  ///            the line.
+  func rangeLocation(_ range: Range<String.Index>) -> ContentLocation {
+    guard let line = self.lines.first(where: { $0.range.contains(range.lowerBound) }) else {
+      return ("", 0, 0)
+    }
+    let offset = templateString.distance(from: line.range.lowerBound, to: range.lowerBound)
+    return (line.content, line.number, offset)
+  }
+}
+
+class Scanner {
+  let originalContent: String
+  var content: String
+  var range: Range<String.UnicodeScalarView.Index>
+
+  /// The start delimiter for a token.
+  private static let tokenStartDelimiter: Unicode.Scalar = "{"
+  /// And the corresponding end delimiter for a token.
+  private static let tokenEndDelimiter: Unicode.Scalar = "}"
+
+  init(_ content: String) {
+    self.originalContent = content
+    self.content = content
+    range = content.unicodeScalars.startIndex..<content.unicodeScalars.startIndex
+  }
+
+  var isEmpty: Bool {
+    content.isEmpty
+  }
+
+  /// Scans for the end of a token, with a specific ending character. If we're
+  /// searching for the end of a block token `%}`, this method receives a `%`.
+  /// The scanner will search for that `%` followed by a `}`.
+  ///
+  /// Note: if the end of a token is found, the `content` and `range`
+  /// properties are updated to reflect this. `content` will be set to what
+  /// remains of the template after the token. `range` will be set to the range
+  /// of the token within the template.
+  ///
+  /// - Parameter tokenChar: The token end character to search for.
+  /// - Returns: The content of a token, or "" if no token end was found.
+  func scanForTokenEnd(_ tokenChar: Unicode.Scalar) -> String {
+    var foundChar = false
+
+    for (index, char) in zip(0..., content.unicodeScalars) {
+      if foundChar && char == Self.tokenEndDelimiter {
+        let result = String(content.unicodeScalars.prefix(index + 1))
+        content = String(content.unicodeScalars.dropFirst(index + 1))
+        range = range.upperBound..<originalContent.unicodeScalars.index(range.upperBound, offsetBy: index + 1)
+        return result
+      } else {
+        foundChar = (char == tokenChar)
+      }
+    }
+
+    content = ""
+    return ""
+  }
+
+  /// Scans for the start of a token, with a list of potential starting
+  /// characters. To scan for the start of variables (`{{`), blocks (`{%`) and
+  /// comments (`{#`), this method receives the characters `{`, `%` and `#`.
+  /// The scanner will search for a `{`, followed by one of the search
+  /// characters. It will give the found character, and the content that came
+  /// before the token.
+  ///
+  /// Note: if the start of a token is found, the `content` and `range`
+  /// properties are updated to reflect this. `content` will be set to what
+  /// remains of the template starting with the token. `range` will be set to
+  /// the start of the token within the template.
+  ///
+  /// - Parameter tokenChars: List of token start characters to search for.
+  /// - Returns: The found token start character, together with the content
+  ///            before the token, or nil of no token start was found.
+  func scanForTokenStart(_ tokenChars: [Unicode.Scalar]) -> (Unicode.Scalar, String)? {
+    var foundBrace = false
+
+    range = range.upperBound..<range.upperBound
+    for (index, char) in zip(0..., content.unicodeScalars) {
+      if foundBrace && tokenChars.contains(char) {
+        let result = String(content.unicodeScalars.prefix(index - 1))
+        content = String(content.unicodeScalars.dropFirst(index - 1))
+        range = range.upperBound..<originalContent.unicodeScalars.index(range.upperBound, offsetBy: index - 1)
+        return (char, result)
+      } else {
+        foundBrace = (char == Self.tokenStartDelimiter)
+      }
+    }
+
+    return nil
+  }
+}
+
+extension String {
+  func findFirstNot(character: Character) -> String.Index? {
+    var index = startIndex
+
+    while index != endIndex {
+      if character != self[index] {
+        return index
+      }
+      index = self.index(after: index)
+    }
+
+    return nil
+  }
+
+  func findLastNot(character: Character) -> String.Index? {
+    var index = self.index(before: endIndex)
+
+    while index != startIndex {
+      if character != self[index] {
+        return self.index(after: index)
+      }
+      index = self.index(before: index)
+    }
+
+    return nil
+  }
+
+  func trim(character: Character) -> String {
+    let first = findFirstNot(character: character) ?? startIndex
+    let last = findLastNot(character: character) ?? endIndex
+    return String(self[first..<last])
+  }
+}
+
+/// Location in some content (text)
+public typealias ContentLocation = (content: String, lineNumber: UInt, lineOffset: Int)

Sources/Stencil/Loader.swift

@@ -1,14 +1,22 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Foundation
 import PathKit
 
-
+/// Type used for loading a template
 public protocol Loader {
+  /// Load a template with the given name
   func loadTemplate(name: String, environment: Environment) throws -> Template
+  /// Load a template with the given list of names
   func loadTemplate(names: [String], environment: Environment) throws -> Template
 }
 
-
 extension Loader {
+  /// Default implementation, tries to load the first template that exists from the list of given names
   public func loadTemplate(names: [String], environment: Environment) throws -> Template {
     for name in names {
       do {
@@ -24,7 +32,6 @@ extension Loader {
   }
 }
 
-
 // A class for loading a template from disk
 public class FileSystemLoader: Loader, CustomStringConvertible {
   public let paths: [Path]
@@ -34,13 +41,13 @@ public class FileSystemLoader: Loader, CustomStringConvertible {
   }
 
   public init(bundle: [Bundle]) {
-    self.paths = bundle.map {
+    self.paths = bundle.map { bundle in
-      return Path($0.bundlePath)
+      Path(bundle.bundlePath)
     }
   }
 
   public var description: String {
-    return "FileSystemLoader(\(paths))"
+    "FileSystemLoader(\(paths))"
   }
 
   public func loadTemplate(name: String, environment: Environment) throws -> Template {
@@ -74,7 +81,6 @@ public class FileSystemLoader: Loader, CustomStringConvertible {
   }
 }
 
-
 public class DictionaryLoader: Loader {
   public let templates: [String: String]
 
@@ -101,7 +107,6 @@ public class DictionaryLoader: Loader {
   }
 }
 
-
 extension Path {
   func safeJoin(path: Path) throws -> Path {
     let newPath = self + path
@@ -114,7 +119,6 @@ extension Path {
   }
 }
 
-
 class SuspiciousFileOperation: Error {
   let basePath: Path
   let path: Path
@@ -125,6 +129,6 @@ class SuspiciousFileOperation: Error {
   }
 
   var description: String {
-    return "Path `\(path)` is located outside of base path `\(basePath)`"
+    "Path `\(path)` is located outside of base path `\(basePath)`"
   }
 }

Sources/Stencil/Node.swift

@@ -0,0 +1,189 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import Foundation
+
+/// Represents a parsed node
+public protocol NodeType {
+  /// Render the node in the given context
+  func render(_ context: Context) throws -> String
+
+  /// Reference to this node's token
+  var token: Token? { get }
+}
+
+/// Render the collection of nodes in the given context
+public func renderNodes(_ nodes: [NodeType], _ context: Context) throws -> String {
+  var result = ""
+
+  for node in nodes {
+    do {
+      result += try node.render(context)
+    } catch {
+      throw error.withToken(node.token)
+    }
+
+    let shouldBreak = context[LoopTerminationNode.breakContextKey] != nil
+    let shouldContinue = context[LoopTerminationNode.continueContextKey] != nil
+
+    if shouldBreak || shouldContinue {
+      break
+    }
+  }
+
+  return result
+}
+
+/// Simple node, used for triggering a closure during rendering
+public class SimpleNode: NodeType {
+  public let handler: (Context) throws -> String
+  public let token: Token?
+
+  public init(token: Token, handler: @escaping (Context) throws -> String) {
+    self.token = token
+    self.handler = handler
+  }
+
+  public func render(_ context: Context) throws -> String {
+    try handler(context)
+  }
+}
+
+/// Represents a block of text, renders the text
+public class TextNode: NodeType {
+  public let text: String
+  public let token: Token?
+  public let trimBehaviour: TrimBehaviour
+
+  public init(text: String, trimBehaviour: TrimBehaviour = .nothing) {
+    self.text = text
+    self.token = nil
+    self.trimBehaviour = trimBehaviour
+  }
+
+  public func render(_ context: Context) throws -> String {
+    var string = self.text
+    if trimBehaviour.leading != .nothing, !string.isEmpty {
+      let range = NSRange(..<string.endIndex, in: string)
+      string = TrimBehaviour.leadingRegex(trim: trimBehaviour.leading)
+        .stringByReplacingMatches(in: string, options: [], range: range, withTemplate: "")
+    }
+    if trimBehaviour.trailing != .nothing, !string.isEmpty {
+      let range = NSRange(..<string.endIndex, in: string)
+      string = TrimBehaviour.trailingRegex(trim: trimBehaviour.trailing)
+        .stringByReplacingMatches(in: string, options: [], range: range, withTemplate: "")
+    }
+    return string
+  }
+}
+
+/// Representing something that can be resolved in a context
+public protocol Resolvable {
+  /// Try to resolve this with the given context
+  func resolve(_ context: Context) throws -> Any?
+}
+
+/// Represents a variable, renders the variable, may have conditional expressions.
+public class VariableNode: NodeType {
+  public let variable: Resolvable
+  public var token: Token?
+  let condition: Expression?
+  let elseExpression: Resolvable?
+
+  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
+    let components = token.components
+
+    func hasToken(_ token: String, at index: Int) -> Bool {
+      components.count > (index + 1) && components[index] == token
+    }
+    func compileResolvable(_ components: [String], containedIn token: Token) throws -> Resolvable {
+      try (try? parser.compileExpression(components: components, token: token)) ??
+        parser.compileFilter(components.joined(separator: " "), containedIn: token)
+    }
+
+    let variable: Resolvable
+    let condition: Expression?
+    let elseExpression: Resolvable?
+
+    if hasToken("if", at: 1) {
+      variable = try compileResolvable([components[0]], containedIn: token)
+
+      let components = components.suffix(from: 2)
+      if let elseIndex = components.firstIndex(of: "else") {
+        condition = try parser.compileExpression(components: Array(components.prefix(upTo: elseIndex)), token: token)
+        let elseToken = Array(components.suffix(from: elseIndex.advanced(by: 1)))
+        elseExpression = try compileResolvable(elseToken, containedIn: token)
+      } else {
+        condition = try parser.compileExpression(components: Array(components), token: token)
+        elseExpression = nil
+      }
+    } else if !components.isEmpty {
+      variable = try compileResolvable(components, containedIn: token)
+      condition = nil
+      elseExpression = nil
+    } else {
+      throw TemplateSyntaxError(reason: "Missing variable name", token: token)
+    }
+
+    return VariableNode(variable: variable, token: token, condition: condition, elseExpression: elseExpression)
+  }
+
+  public init(variable: Resolvable, token: Token? = nil) {
+    self.variable = variable
+    self.token = token
+    self.condition = nil
+    self.elseExpression = nil
+  }
+
+  init(variable: Resolvable, token: Token? = nil, condition: Expression?, elseExpression: Resolvable?) {
+    self.variable = variable
+    self.token = token
+    self.condition = condition
+    self.elseExpression = elseExpression
+  }
+
+  public init(variable: String, token: Token? = nil) {
+    self.variable = Variable(variable)
+    self.token = token
+    self.condition = nil
+    self.elseExpression = nil
+  }
+
+  public func render(_ context: Context) throws -> String {
+    if let condition = self.condition, try condition.evaluate(context: context) == false {
+      return try elseExpression?.resolve(context).map(stringify) ?? ""
+    }
+
+    let result = try variable.resolve(context)
+    return stringify(result)
+  }
+}
+
+func stringify(_ result: Any?) -> String {
+  if let result = result as? String {
+    return result
+  } else if let array = result as? [Any?] {
+    return unwrap(array).description
+  } else if let result = result as? CustomStringConvertible {
+    return result.description
+  } else if let result = result as? NSObject {
+    return result.description
+  }
+
+  return ""
+}
+
+func unwrap(_ array: [Any?]) -> [Any] {
+  array.map { (item: Any?) -> Any in
+    if let item = item {
+      if let items = item as? [Any?] {
+        return unwrap(items)
+      } else {
+        return item
+      }
+    } else { return item as Any }
+  }
+}

Sources/Stencil/NowTag.swift

@@ -1,43 +1,50 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 #if !os(Linux)
 import Foundation
 
+class NowNode: NodeType {
+  let format: Variable
+  let token: Token?
 
-class NowNode : NodeType {
+  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
-  let format:Variable
+    var format: Variable?
 
-  class func parse(_ parser:TokenParser, token:Token) throws -> NodeType {
+    let components = token.components
-    var format:Variable?
-
-    let components = token.components()
     guard components.count <= 2 else {
-      throw TemplateSyntaxError("'now' tags may only have one argument: the format string `\(token.contents)`.")
+      throw TemplateSyntaxError("'now' tags may only have one argument: the format string.")
     }
     if components.count == 2 {
       format = Variable(components[1])
     }
 
-    return NowNode(format:format)
+    return NowNode(format: format, token: token)
   }
 
-  init(format:Variable?) {
+  init(format: Variable?, token: Token? = nil) {
     self.format = format ?? Variable("\"yyyy-MM-dd 'at' HH:mm\"")
+    self.token = token
   }
 
   func render(_ context: Context) throws -> String {
     let date = Date()
     let format = try self.format.resolve(context)
-    var formatter:DateFormatter?
 
+    var formatter: DateFormatter
     if let format = format as? DateFormatter {
       formatter = format
     } else if let format = format as? String {
       formatter = DateFormatter()
-      formatter!.dateFormat = format
+      formatter.dateFormat = format
     } else {
       return ""
     }
 
-    return formatter!.string(from: date)
+    return formatter.string(from: date)
   }
 }
 #endif

Sources/Stencil/Parser.swift

@@ -0,0 +1,278 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+/// Creates a checker that will stop parsing if it encounters a list of tags.
+/// Useful for example for scanning until a given "end"-node.
+public func until(_ tags: [String]) -> ((TokenParser, Token) -> Bool) {
+  { _, token in
+    if let name = token.components.first {
+      for tag in tags where name == tag {
+        return true
+      }
+    }
+
+    return false
+  }
+}
+
+/// A class for parsing an array of tokens and converts them into a collection of Node's
+public class TokenParser {
+  /// Parser for finding a kind of node
+  public typealias TagParser = (TokenParser, Token) throws -> NodeType
+
+  fileprivate var tokens: [Token]
+  fileprivate(set) var parsedTokens: [Token] = []
+  fileprivate let environment: Environment
+  fileprivate var previousWhiteSpace: WhitespaceBehaviour.Behaviour?
+
+  /// Simple initializer
+  public init(tokens: [Token], environment: Environment) {
+    self.tokens = tokens
+    self.environment = environment
+  }
+
+  /// Parse the given tokens into nodes
+  public func parse() throws -> [NodeType] {
+    try parse(nil)
+  }
+
+  /// Parse nodes until a specific "something" is detected, determined by the provided closure.
+  /// Combine this with the `until(:)` function above to scan nodes until a given token.
+  public func parse(_ parseUntil: ((_ parser: TokenParser, _ token: Token) -> (Bool))?) throws -> [NodeType] {
+    var nodes = [NodeType]()
+
+    while !tokens.isEmpty {
+      guard let token = nextToken() else { break }
+
+      switch token.kind {
+      case .text:
+        nodes.append(TextNode(text: token.contents, trimBehaviour: trimBehaviour))
+      case .variable:
+        previousWhiteSpace = nil
+        try nodes.append(VariableNode.parse(self, token: token))
+      case .block:
+        previousWhiteSpace = token.whitespace?.trailing
+        if let parseUntil = parseUntil, parseUntil(self, token) {
+          prependToken(token)
+          return nodes
+        }
+
+        if var tag = token.components.first {
+          do {
+            // special case for labeled tags (such as for loops)
+            if tag.hasSuffix(":") && token.components.count >= 2 {
+              tag = token.components[1]
+            }
+
+            let parser = try environment.findTag(name: tag)
+            let node = try parser(self, token)
+            nodes.append(node)
+          } catch {
+            throw error.withToken(token)
+          }
+        }
+      case .comment:
+        previousWhiteSpace = nil
+        continue
+      }
+    }
+
+    return nodes
+  }
+
+  /// Pop the next token (returning it)
+  public func nextToken() -> Token? {
+    if !tokens.isEmpty {
+      let nextToken = tokens.remove(at: 0)
+      parsedTokens.append(nextToken)
+      return nextToken
+    }
+
+    return nil
+  }
+
+  func peekWhitespace() -> WhitespaceBehaviour.Behaviour? {
+    tokens.first?.whitespace?.leading
+  }
+
+  /// Insert a token 
+  public func prependToken(_ token: Token) {
+    tokens.insert(token, at: 0)
+    if parsedTokens.last == token {
+      parsedTokens.removeLast()
+    }
+  }
+
+  /// Create filter expression from a string contained in provided token
+  public func compileFilter(_ filterToken: String, containedIn token: Token) throws -> Resolvable {
+    try environment.compileFilter(filterToken, containedIn: token)
+  }
+
+  /// Create boolean expression from components contained in provided token
+  public func compileExpression(components: [String], token: Token) throws -> Expression {
+    try environment.compileExpression(components: components, containedIn: token)
+  }
+
+  /// Create resolvable (i.e. range variable or filter expression) from a string contained in provided token
+  public func compileResolvable(_ token: String, containedIn containingToken: Token) throws -> Resolvable {
+    try environment.compileResolvable(token, containedIn: containingToken)
+  }
+
+  private var trimBehaviour: TrimBehaviour {
+    var behaviour: TrimBehaviour = .nothing
+
+    if let leading = previousWhiteSpace {
+      if leading == .unspecified {
+        behaviour.leading = environment.trimBehaviour.trailing
+      } else {
+        behaviour.leading = leading == .trim ? .whitespaceAndNewLines : .nothing
+      }
+    }
+    if let trailing = peekWhitespace() {
+      if trailing == .unspecified {
+        behaviour.trailing = environment.trimBehaviour.leading
+      } else {
+        behaviour.trailing = trailing == .trim ? .whitespaceAndNewLines : .nothing
+      }
+    }
+
+    return behaviour
+  }
+}
+
+extension Environment {
+  func findTag(name: String) throws -> Extension.TagParser {
+    for ext in extensions {
+      if let filter = ext.tags[name] {
+        return filter
+      }
+    }
+
+    throw TemplateSyntaxError("Unknown template tag '\(name)'")
+  }
+
+  func findFilter(_ name: String) throws -> FilterType {
+    for ext in extensions {
+      if let filter = ext.filters[name] {
+        return filter
+      }
+    }
+
+    let suggestedFilters = self.suggestedFilters(for: name)
+    if suggestedFilters.isEmpty {
+      throw TemplateSyntaxError("Unknown filter '\(name)'.")
+    } else {
+      throw TemplateSyntaxError(
+        """
+        Unknown filter '\(name)'. \
+        Found similar filters: \(suggestedFilters.map { "'\($0)'" }.joined(separator: ", ")).
+        """
+      )
+    }
+  }
+
+  private func suggestedFilters(for name: String) -> [String] {
+    let allFilters = extensions.flatMap { $0.filters.keys }
+
+    let filtersWithDistance = allFilters
+      .map { (filterName: $0, distance: $0.levenshteinDistance(name)) }
+      // do not suggest filters which names are shorter than the distance
+      .filter { $0.filterName.count > $0.distance }
+    guard let minDistance = filtersWithDistance.min(by: { $0.distance < $1.distance })?.distance else {
+      return []
+    }
+    // suggest all filters with the same distance
+    return filtersWithDistance.filter { $0.distance == minDistance }.map { $0.filterName }
+  }
+
+  /// Create filter expression from a string
+  public func compileFilter(_ token: String) throws -> Resolvable {
+    try FilterExpression(token: token, environment: self)
+  }
+
+  /// Create filter expression from a string contained in provided token
+  public func compileFilter(_ filterToken: String, containedIn containingToken: Token) throws -> Resolvable {
+    do {
+      return try FilterExpression(token: filterToken, environment: self)
+    } catch {
+      guard var syntaxError = error as? TemplateSyntaxError, syntaxError.token == nil else {
+        throw error
+      }
+      // find offset of filter in the containing token so that only filter is highligted, not the whole token
+      if let filterTokenRange = containingToken.contents.range(of: filterToken) {
+        var location = containingToken.sourceMap.location
+        location.lineOffset += containingToken.contents.distance(
+          from: containingToken.contents.startIndex,
+          to: filterTokenRange.lowerBound
+        )
+        syntaxError.token = .variable(
+          value: filterToken,
+          at: SourceMap(filename: containingToken.sourceMap.filename, location: location)
+        )
+      } else {
+        syntaxError.token = containingToken
+      }
+      throw syntaxError
+    }
+  }
+
+  /// Create resolvable (i.e. range variable or filter expression) from a string
+  public func compileResolvable(_ token: String) throws -> Resolvable {
+    try RangeVariable(token, environment: self)
+      ?? compileFilter(token)
+  }
+
+  /// Create resolvable (i.e. range variable or filter expression) from a string contained in provided token
+  public func compileResolvable(_ token: String, containedIn containingToken: Token) throws -> Resolvable {
+    try RangeVariable(token, environment: self, containedIn: containingToken)
+      ?? compileFilter(token, containedIn: containingToken)
+  }
+
+  /// Create boolean expression from components contained in provided token
+  public func compileExpression(components: [String], containedIn token: Token) throws -> Expression {
+    try IfExpressionParser.parser(components: components, environment: self, token: token).parse()
+  }
+}
+
+// https://en.wikipedia.org/wiki/Levenshtein_distance#Iterative_with_two_matrix_rows
+extension String {
+  subscript(_ index: Int) -> Character {
+    self[self.index(self.startIndex, offsetBy: index)]
+  }
+
+  func levenshteinDistance(_ target: String) -> Int {
+    // create two work vectors of integer distances
+    var last, current: [Int]
+
+    // initialize v0 (the previous row of distances)
+    // this row is A[0][i]: edit distance for an empty s
+    // the distance is just the number of characters to delete from t
+    last = [Int](0...target.count)
+    current = [Int](repeating: 0, count: target.count + 1)
+
+    for selfIndex in 0..<self.count {
+      // calculate v1 (current row distances) from the previous row v0
+
+      // first element of v1 is A[i+1][0]
+      //   edit distance is delete (i+1) chars from s to match empty t
+      current[0] = selfIndex + 1
+
+      // use formula to fill in the rest of the row
+      for targetIndex in 0..<target.count {
+        current[targetIndex + 1] = Swift.min(
+          last[targetIndex + 1] + 1,
+          current[targetIndex] + 1,
+          last[targetIndex] + (self[selfIndex] == target[targetIndex] ? 0 : 1)
+        )
+      }
+
+      // copy v1 (current row) to v0 (previous row) for next iteration
+      last = current
+    }
+
+    return current[target.count]
+  }
+}

Sources/Stencil/Template.swift

@@ -1,14 +1,24 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Foundation
 import PathKit
 
 #if os(Linux)
+// swiftlint:disable:next prefixed_toplevel_constant
 let NSFileNoSuchFileError = 4
 #endif
 
 /// A class representing a template
 open class Template: ExpressibleByStringLiteral {
-  let environment: Environment
+  let templateString: String
-  let tokens: [Token]
+  var environment: Environment
+
+  /// The list of parsed (lexed) tokens
+  public let tokens: [Token]
 
   /// The name of the loaded Template if the Template was loaded from a Loader
   public let name: String?
@@ -17,25 +27,26 @@ open class Template: ExpressibleByStringLiteral {
   public required init(templateString: String, environment: Environment? = nil, name: String? = nil) {
     self.environment = environment ?? Environment()
     self.name = name
+    self.templateString = templateString
 
-    let lexer = Lexer(templateString: templateString)
+    let lexer = Lexer(templateName: name, templateString: templateString)
     tokens = lexer.tokenize()
   }
 
   /// Create a template with the given name inside the given bundle
   @available(*, deprecated, message: "Use Environment/FileSystemLoader instead")
-  public convenience init(named:String, inBundle bundle:Bundle? = nil) throws {
+  public convenience init(named: String, inBundle bundle: Bundle? = nil) throws {
-    let useBundle = bundle ??  Bundle.main
+    let useBundle = bundle ?? Bundle.main
     guard let url = useBundle.url(forResource: named, withExtension: nil) else {
       throw NSError(domain: NSCocoaErrorDomain, code: NSFileNoSuchFileError, userInfo: nil)
     }
 
-    try self.init(URL:url)
+    try self.init(URL: url)
   }
 
   /// Create a template with a file found at the given URL
   @available(*, deprecated, message: "Use Environment/FileSystemLoader instead")
-  public convenience init(URL:Foundation.URL) throws {
+  public convenience init(URL: Foundation.URL) throws {
     try self.init(path: Path(URL.path))
   }
 
@@ -48,30 +59,31 @@ open class Template: ExpressibleByStringLiteral {
   // MARK: ExpressibleByStringLiteral
 
   // Create a templaVte with a template string literal
-  public convenience required init(stringLiteral value: String) {
+  public required convenience init(stringLiteral value: String) {
     self.init(templateString: value)
   }
 
   // Create a template with a template string literal
-  public convenience required init(extendedGraphemeClusterLiteral value: StringLiteralType) {
+  public required convenience init(extendedGraphemeClusterLiteral value: StringLiteralType) {
     self.init(stringLiteral: value)
   }
 
   // Create a template with a template string literal
-  public convenience required init(unicodeScalarLiteral value: StringLiteralType) {
+  public required convenience init(unicodeScalarLiteral value: StringLiteralType) {
     self.init(stringLiteral: value)
   }
 
   /// Render the given template with a context
-  func render(_ context: Context) throws -> String {
+  public func render(_ context: Context) throws -> String {
     let context = context
     let parser = TokenParser(tokens: tokens, environment: context.environment)
     let nodes = try parser.parse()
     return try renderNodes(nodes, context)
   }
 
+  // swiftlint:disable discouraged_optional_collection
   /// Render the given template
   open func render(_ dictionary: [String: Any]? = nil) throws -> String {
-    return try render(Context(dictionary: dictionary, environment: environment))
+    try render(Context(dictionary: dictionary ?? [:], environment: environment))
   }
 }

Sources/Stencil/Tokenizer.swift

@@ -0,0 +1,160 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import Foundation
+
+extension String {
+  /// Split a string by a separator leaving quoted phrases together
+  func smartSplit(separator: Character = " ") -> [String] {
+    var word = ""
+    var components: [String] = []
+    var separate: Character = separator
+    var singleQuoteCount = 0
+    var doubleQuoteCount = 0
+
+    for character in self {
+      if character == "'" {
+        singleQuoteCount += 1
+      } else if character == "\"" {
+        doubleQuoteCount += 1
+      }
+
+      if character == separate {
+        if separate != separator {
+          word.append(separate)
+        } else if (singleQuoteCount.isMultiple(of: 2) || doubleQuoteCount.isMultiple(of: 2)) && !word.isEmpty {
+          appendWord(word, to: &components)
+          word = ""
+        }
+
+        separate = separator
+      } else {
+        if separate == separator && (character == "'" || character == "\"") {
+          separate = character
+        }
+        word.append(character)
+      }
+    }
+
+    if !word.isEmpty {
+      appendWord(word, to: &components)
+    }
+
+    return components
+  }
+
+  private func appendWord(_ word: String, to components: inout [String]) {
+    let specialCharacters = ",|:"
+
+    if !components.isEmpty {
+      if let precedingChar = components.last?.last, specialCharacters.contains(precedingChar) {
+        // special case for labeled for-loops
+        if components.count == 1 && word == "for" {
+          components.append(word)
+        } else {
+          components[components.count - 1] += word
+        }
+      } else if specialCharacters.contains(word) {
+        components[components.count - 1] += word
+      } else if word != "(" && word.first == "(" || word != ")" && word.first == ")" {
+        components.append(String(word.prefix(1)))
+        appendWord(String(word.dropFirst()), to: &components)
+      } else if word != "(" && word.last == "(" || word != ")" && word.last == ")" {
+        appendWord(String(word.dropLast()), to: &components)
+        components.append(String(word.suffix(1)))
+      } else {
+        components.append(word)
+      }
+    } else {
+      components.append(word)
+    }
+  }
+}
+
+public struct SourceMap: Equatable {
+  public let filename: String?
+  public let location: ContentLocation
+
+  init(filename: String? = nil, location: ContentLocation = ("", 0, 0)) {
+    self.filename = filename
+    self.location = location
+  }
+
+  static let unknown = SourceMap()
+
+  public static func == (lhs: SourceMap, rhs: SourceMap) -> Bool {
+    lhs.filename == rhs.filename && lhs.location == rhs.location
+  }
+}
+
+public struct WhitespaceBehaviour: Equatable {
+  public enum Behaviour {
+    case unspecified
+    case trim
+    case keep
+  }
+
+  let leading: Behaviour
+  let trailing: Behaviour
+
+  public static let unspecified = WhitespaceBehaviour(leading: .unspecified, trailing: .unspecified)
+}
+
+public class Token: Equatable {
+  public enum Kind: Equatable {
+    /// A token representing a piece of text.
+    case text
+    /// A token representing a variable.
+    case variable
+    /// A token representing a comment.
+    case comment
+    /// A token representing a template block.
+    case block
+  }
+
+  public let contents: String
+  public let kind: Kind
+  public let sourceMap: SourceMap
+  public var whitespace: WhitespaceBehaviour?
+
+  /// Returns the underlying value as an array seperated by spaces
+  public private(set) lazy var components: [String] = self.contents.smartSplit()
+
+  init(contents: String, kind: Kind, sourceMap: SourceMap, whitespace: WhitespaceBehaviour? = nil) {
+    self.contents = contents
+    self.kind = kind
+    self.sourceMap = sourceMap
+    self.whitespace = whitespace
+  }
+
+  /// A token representing a piece of text.
+  public static func text(value: String, at sourceMap: SourceMap) -> Token {
+    Token(contents: value, kind: .text, sourceMap: sourceMap)
+  }
+
+  /// A token representing a variable.
+  public static func variable(value: String, at sourceMap: SourceMap) -> Token {
+    Token(contents: value, kind: .variable, sourceMap: sourceMap)
+  }
+
+  /// A token representing a comment.
+  public static func comment(value: String, at sourceMap: SourceMap) -> Token {
+    Token(contents: value, kind: .comment, sourceMap: sourceMap)
+  }
+
+  /// A token representing a template block.
+  public static func block(
+    value: String,
+    at sourceMap: SourceMap,
+    whitespace: WhitespaceBehaviour = .unspecified
+  ) -> Token {
+    Token(contents: value, kind: .block, sourceMap: sourceMap, whitespace: whitespace)
+  }
+
+  public static func == (lhs: Token, rhs: Token) -> Bool {
+    lhs.contents == rhs.contents && lhs.kind == rhs.kind && lhs.sourceMap == rhs.sourceMap
+  }
+}

Sources/Stencil/TrimBehaviour.swift

@@ -0,0 +1,76 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import Foundation
+
+public struct TrimBehaviour: Equatable {
+  var leading: Trim
+  var trailing: Trim
+
+  public enum Trim {
+    /// nothing
+    case nothing
+
+    /// tabs and spaces
+    case whitespace
+
+    /// tabs and spaces and a single new line
+    case whitespaceAndOneNewLine
+
+    /// all tabs spaces and newlines
+    case whitespaceAndNewLines
+  }
+
+  public init(leading: Trim, trailing: Trim) {
+    self.leading = leading
+    self.trailing = trailing
+  }
+
+  /// doesn't touch newlines
+  public static let nothing = TrimBehaviour(leading: .nothing, trailing: .nothing)
+
+  /// removes whitespace before a block and whitespace and a single newline after a block
+  public static let smart = TrimBehaviour(leading: .whitespace, trailing: .whitespaceAndOneNewLine)
+
+  /// removes all whitespace and newlines before and after a block
+  public static let all = TrimBehaviour(leading: .whitespaceAndNewLines, trailing: .whitespaceAndNewLines)
+
+  static func leadingRegex(trim: Trim) -> NSRegularExpression {
+    switch trim {
+    case .nothing:
+      fatalError("No RegularExpression for none")
+    case .whitespace:
+      return Self.leadingWhitespace
+    case .whitespaceAndOneNewLine:
+      return Self.leadingWhitespaceAndOneNewLine
+    case .whitespaceAndNewLines:
+      return Self.leadingWhitespaceAndNewlines
+    }
+  }
+
+  static func trailingRegex(trim: Trim) -> NSRegularExpression {
+    switch trim {
+    case .nothing:
+      fatalError("No RegularExpression for none")
+    case .whitespace:
+      return Self.trailingWhitespace
+    case .whitespaceAndOneNewLine:
+      return Self.trailingWhitespaceAndOneNewLine
+    case .whitespaceAndNewLines:
+      return Self.trailingWhitespaceAndNewLines
+    }
+  }
+
+  // swiftlint:disable force_try
+  private static let leadingWhitespaceAndNewlines = try! NSRegularExpression(pattern: "^\\s+")
+  private static let trailingWhitespaceAndNewLines = try! NSRegularExpression(pattern: "\\s+$")
+
+  private static let leadingWhitespaceAndOneNewLine = try! NSRegularExpression(pattern: "^[ \t]*\n")
+  private static let trailingWhitespaceAndOneNewLine = try! NSRegularExpression(pattern: "\n[ \t]*$")
+
+  private static let leadingWhitespace = try! NSRegularExpression(pattern: "^[ \t]*")
+  private static let trailingWhitespace = try! NSRegularExpression(pattern: "[ \t]*$")
+}

Sources/Stencil/Variable.swift

@@ -0,0 +1,291 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import Foundation
+
+typealias Number = Float
+
+class FilterExpression: Resolvable {
+  let filters: [(FilterType, [Variable])]
+  let variable: Variable
+
+  init(token: String, environment: Environment) throws {
+    let bits = token.smartSplit(separator: "|").map { String($0).trim(character: " ") }
+    if bits.isEmpty {
+      throw TemplateSyntaxError("Variable tags must include at least 1 argument")
+    }
+
+    variable = Variable(bits[0])
+    let filterBits = bits[bits.indices.suffix(from: 1)]
+
+    do {
+      filters = try filterBits.map { bit in
+        let (name, arguments) = parseFilterComponents(token: bit)
+        let filter = try environment.findFilter(name)
+        return (filter, arguments)
+      }
+    } catch {
+      filters = []
+      throw error
+    }
+  }
+
+  func resolve(_ context: Context) throws -> Any? {
+    let result = try variable.resolve(context)
+
+    return try filters.reduce(result) { value, filter in
+      let arguments = try filter.1.map { try $0.resolve(context) }
+      return try filter.0.invoke(value: value, arguments: arguments, context: context)
+    }
+  }
+}
+
+/// A structure used to represent a template variable, and to resolve it in a given context.
+public struct Variable: Equatable, Resolvable {
+  public let variable: String
+
+  /// Create a variable with a string representing the variable
+  public init(_ variable: String) {
+    self.variable = variable
+  }
+
+  /// Resolve the variable in the given context
+  public func resolve(_ context: Context) throws -> Any? {
+    if variable.count > 1 &&
+      ((variable.hasPrefix("'") && variable.hasSuffix("'")) || (variable.hasPrefix("\"") && variable.hasSuffix("\""))) {
+      // String literal
+      return String(variable[variable.index(after: variable.startIndex) ..< variable.index(before: variable.endIndex)])
+    }
+
+    // Number literal
+    if let int = Int(variable) {
+      return int
+    }
+    if let number = Number(variable) {
+      return number
+    }
+    // Boolean literal
+    if let bool = Bool(variable) {
+      return bool
+    }
+
+    var current: Any? = context
+    for bit in try lookup(context) {
+      current = resolve(bit: bit, context: current)
+
+      if current == nil {
+        return nil
+      } else if let lazyCurrent = current as? LazyValueWrapper {
+        current = try lazyCurrent.value(context: context)
+      }
+    }
+
+    if let resolvable = current as? Resolvable {
+      current = try resolvable.resolve(context)
+    } else if let node = current as? NodeType {
+      current = try node.render(context)
+    }
+
+    return normalize(current)
+  }
+
+  // Split the lookup string and resolve references if possible
+  private func lookup(_ context: Context) throws -> [String] {
+    let keyPath = KeyPath(variable, in: context)
+    return try keyPath.parse()
+  }
+
+  // Try to resolve a partial keypath for the given context
+  private func resolve(bit: String, context: Any?) -> Any? {
+    let context = normalize(context)
+
+    if let context = context as? Context {
+      return context[bit]
+    } else if let dictionary = context as? [String: Any] {
+      return resolve(bit: bit, dictionary: dictionary)
+    } else if let array = context as? [Any] {
+      return resolve(bit: bit, collection: array)
+    } else if let string = context as? String {
+      return resolve(bit: bit, collection: string)
+    } else if let value = context as? DynamicMemberLookup {
+      return value[dynamicMember: bit]
+    } else if let object = context as? NSObject {  // NSKeyValueCoding
+      #if !canImport(ObjectiveC)
+        return nil
+      #else
+        if object.responds(to: Selector(bit)) {
+          return object.value(forKey: bit)
+        }
+      #endif
+    } else if let value = context {
+      return Mirror(reflecting: value).getValue(for: bit)
+    }
+
+    return nil
+  }
+
+  // Try to resolve a partial keypath for the given dictionary
+  private func resolve(bit: String, dictionary: [String: Any]) -> Any? {
+    if bit == "count" {
+      return dictionary.count
+    } else {
+      return dictionary[bit]
+    }
+  }
+
+  // Try to resolve a partial keypath for the given collection
+  private func resolve<T: Collection>(bit: String, collection: T) -> Any? {
+    if let index = Int(bit) {
+      if index >= 0 && index < collection.count {
+        return collection[collection.index(collection.startIndex, offsetBy: index)]
+      } else {
+        return nil
+      }
+    } else if bit == "first" {
+      return collection.first
+    } else if bit == "last" {
+      return collection[collection.index(collection.endIndex, offsetBy: -1)]
+    } else if bit == "count" {
+      return collection.count
+    } else {
+      return nil
+    }
+  }
+}
+
+/// A structure used to represet range of two integer values expressed as `from...to`.
+/// Values should be numbers (they will be converted to integers).
+/// Rendering this variable produces array from range `from...to`.
+/// If `from` is more than `to` array will contain values of reversed range.
+public struct RangeVariable: Resolvable {
+  public let from: Resolvable
+  // swiftlint:disable:next identifier_name
+  public let to: Resolvable
+
+  public init?(_ token: String, environment: Environment) throws {
+    let components = token.components(separatedBy: "...")
+    guard components.count == 2 else {
+      return nil
+    }
+
+    self.from = try environment.compileFilter(components[0])
+    self.to = try environment.compileFilter(components[1])
+  }
+
+  public init?(_ token: String, environment: Environment, containedIn containingToken: Token) throws {
+    let components = token.components(separatedBy: "...")
+    guard components.count == 2 else {
+      return nil
+    }
+
+    self.from = try environment.compileFilter(components[0], containedIn: containingToken)
+    self.to = try environment.compileFilter(components[1], containedIn: containingToken)
+  }
+
+  public func resolve(_ context: Context) throws -> Any? {
+    let lowerResolved = try from.resolve(context)
+    let upperResolved = try to.resolve(context)
+
+    guard let lower = lowerResolved.flatMap(toNumber(value:)).flatMap(Int.init) else {
+      throw TemplateSyntaxError("'from' value is not an Integer (\(lowerResolved ?? "nil"))")
+    }
+
+    guard let upper = upperResolved.flatMap(toNumber(value:)).flatMap(Int.init) else {
+      throw TemplateSyntaxError("'to' value is not an Integer (\(upperResolved ?? "nil") )")
+    }
+
+    let range = min(lower, upper)...max(lower, upper)
+    return lower > upper ? Array(range.reversed()) : Array(range)
+  }
+}
+
+func normalize(_ current: Any?) -> Any? {
+  if let current = current as? Normalizable {
+    return current.normalize()
+  }
+
+  return current
+}
+
+protocol Normalizable {
+  func normalize() -> Any?
+}
+
+extension Array: Normalizable {
+  func normalize() -> Any? {
+    map { $0 as Any }
+  }
+}
+
+// swiftlint:disable:next legacy_objc_type
+extension NSArray: Normalizable {
+  func normalize() -> Any? {
+    map { $0 as Any }
+  }
+}
+
+extension Dictionary: Normalizable {
+  func normalize() -> Any? {
+    var dictionary: [String: Any] = [:]
+
+    for (key, value) in self {
+      if let key = key as? String {
+        dictionary[key] = Stencil.normalize(value)
+      } else if let key = key as? CustomStringConvertible {
+        dictionary[key.description] = Stencil.normalize(value)
+      }
+    }
+
+    return dictionary
+  }
+}
+
+func parseFilterComponents(token: String) -> (String, [Variable]) {
+  var components = token.smartSplit(separator: ":")
+  let name = components.removeFirst().trim(character: " ")
+  let variables = components
+    .joined(separator: ":")
+    .smartSplit(separator: ",")
+    .map { Variable($0.trim(character: " ")) }
+  return (name, variables)
+}
+
+extension Mirror {
+  func getValue(for key: String) -> Any? {
+    let result = descendant(key) ?? Int(key).flatMap { descendant($0) }
+    if result == nil {
+      // go through inheritance chain to reach superclass properties
+      return superclassMirror?.getValue(for: key)
+    } else if let result = result {
+      guard String(describing: result) != "nil" else {
+        // mirror returns non-nil value even for nil-containing properties
+        // so we have to check if its value is actually nil or not
+        return nil
+      }
+      if let result = (result as? AnyOptional)?.wrapped {
+        return result
+      } else {
+        return result
+      }
+    }
+    return result
+  }
+}
+
+protocol AnyOptional {
+  var wrapped: Any? { get }
+}
+
+extension Optional: AnyOptional {
+  var wrapped: Any? {
+    switch self {
+    case let .some(value):
+      return value
+    case .none:
+      return nil
+    }
+  }
+}

Sources/Tokenizer.swift

@@ -1,99 +0,0 @@
-import Foundation
-
-
-extension String {
-  /// Split a string by a separator leaving quoted phrases together
-  func smartSplit(separator: Character = " ") -> [String] {
-    var word = ""
-    var components: [String] = []
-    var separate: Character = separator
-    var singleQuoteCount = 0
-    var doubleQuoteCount = 0
-
-    for character in self.characters {
-      if character == "'" { singleQuoteCount += 1 }
-      else if character == "\"" { doubleQuoteCount += 1 }
-
-      if character == separate {
-
-        if separate != separator {
-          word.append(separate)
-        } else if singleQuoteCount % 2 == 0 && doubleQuoteCount % 2 == 0 && !word.isEmpty {
-          components.append(word)
-          word = ""
-        }
-
-        separate = separator
-      } else {
-        if separate == separator && (character == "'" || character == "\"") {
-          separate = character
-        }
-        word.append(character)
-      }
-    }
-
-    if !word.isEmpty {
-      components.append(word)
-    }
-
-    return components
-  }
-}
-
-
-public enum Token : Equatable {
-  /// A token representing a piece of text.
-  case text(value: String)
-
-  /// A token representing a variable.
-  case variable(value: String)
-
-  /// A token representing a comment.
-  case comment(value: String)
-
-  /// A token representing a template block.
-  case block(value: String)
-
-  /// Returns the underlying value as an array seperated by spaces
-  public func components() -> [String] {
-    switch self {
-    case .block(let value):
-      return value.smartSplit()
-    case .variable(let value):
-      return value.smartSplit()
-    case .text(let value):
-      return value.smartSplit()
-    case .comment(let value):
-      return value.smartSplit()
-    }
-  }
-
-  public var contents: String {
-    switch self {
-    case .block(let value):
-      return value
-    case .variable(let value):
-      return value
-    case .text(let value):
-      return value
-    case .comment(let value):
-      return value
-    }
-  }
-}
-
-
-public func == (lhs: Token, rhs: Token) -> Bool {
-  switch (lhs, rhs) {
-  case (.text(let lhsValue), .text(let rhsValue)):
-    return lhsValue == rhsValue
-  case (.variable(let lhsValue), .variable(let rhsValue)):
-    return lhsValue == rhsValue
-  case (.block(let lhsValue), .block(let rhsValue)):
-    return lhsValue == rhsValue
-  case (.comment(let lhsValue), .comment(let rhsValue)):
-    return lhsValue == rhsValue
-  default:
-    return false
-  }
-}

Sources/Variable.swift

@@ -1,181 +0,0 @@
-import Foundation
-
-
-typealias Number = Float
-
-
-class FilterExpression : Resolvable {
-  let filters: [(FilterType, [Variable])]
-  let variable: Variable
-
-  init(token: String, parser: TokenParser) throws {
-    let bits = token.characters.split(separator: "|").map({ String($0).trim(character: " ") })
-    if bits.isEmpty {
-      filters = []
-      variable = Variable("")
-      throw TemplateSyntaxError("Variable tags must include at least 1 argument")
-    }
-
-    variable = Variable(bits[0])
-    let filterBits = bits[bits.indices.suffix(from: 1)]
-
-    do {
-      filters = try filterBits.map {
-        let (name, arguments) = parseFilterComponents(token: $0)
-        let filter = try parser.findFilter(name)
-        return (filter, arguments)
-      }
-    } catch {
-      filters = []
-      throw error
-    }
-  }
-
-  func resolve(_ context: Context) throws -> Any? {
-    let result = try variable.resolve(context)
-
-    return try filters.reduce(result) { x, y in
-      let arguments = try y.1.map { try $0.resolve(context) }
-      return try y.0.invoke(value: x, arguments: arguments)
-    }
-  }
-}
-
-/// A structure used to represent a template variable, and to resolve it in a given context.
-public struct Variable : Equatable, Resolvable {
-  public let variable: String
-
-  /// Create a variable with a string representing the variable
-  public init(_ variable: String) {
-    self.variable = variable
-  }
-
-  fileprivate func lookup() -> [String] {
-    return variable.characters.split(separator: ".").map(String.init)
-  }
-
-  /// Resolve the variable in the given context
-  public func resolve(_ context: Context) throws -> Any? {
-    var current: Any? = context
-
-    if (variable.hasPrefix("'") && variable.hasSuffix("'")) || (variable.hasPrefix("\"") && variable.hasSuffix("\"")) {
-      // String literal
-      return variable[variable.characters.index(after: variable.startIndex) ..< variable.characters.index(before: variable.endIndex)]
-    }
-
-    if let number = Number(variable) {
-      // Number literal
-      return number
-    }
-
-    for bit in lookup() {
-      current = normalize(current)
-
-      if let context = current as? Context {
-        current = context[bit]
-      } else if let dictionary = current as? [String: Any] {
-        if bit == "count" {
-          current = dictionary.count
-        } else {
-          current = dictionary[bit]
-        }
-      } else if let array = current as? [Any] {
-        if let index = Int(bit) {
-          if index >= 0 && index < array.count {
-            current = array[index]
-          } else {
-            current = nil
-          }
-        } else if bit == "first" {
-          current = array.first
-        } else if bit == "last" {
-          current = array.last
-        } else if bit == "count" {
-          current = array.count
-        }
-      } else if let object = current as? NSObject {  // NSKeyValueCoding
-#if os(Linux)
-        return nil
-#else
-        current = object.value(forKey: bit)
-#endif
-      } else if let value = current {
-        let mirror = Mirror(reflecting: value)
-        current = mirror.descendant(bit)
-
-        if current == nil {
-          return nil
-          // mirror returns non-nil value even for nil-containing properties
-          // so we have to check if its value is actually nil or not
-        } else if let current = current, String(describing: current) == "nil" {
-          return nil
-        }
-      } else {
-        return nil
-      }
-    }
-
-    if let resolvable = current as? Resolvable {
-      current = try resolvable.resolve(context)
-    } else if let node = current as? NodeType {
-      current = try node.render(context)
-    }
-
-    return normalize(current)
-  }
-}
-
-public func ==(lhs: Variable, rhs: Variable) -> Bool {
-  return lhs.variable == rhs.variable
-}
-
-
-func normalize(_ current: Any?) -> Any? {
-  if let current = current as? Normalizable {
-    return current.normalize()
-  }
-
-  return current
-}
-
-protocol Normalizable {
-  func normalize() -> Any?
-}
-
-extension Array : Normalizable {
-  func normalize() -> Any? {
-    return map { $0 as Any }
-  }
-}
-
-extension NSArray : Normalizable {
-  func normalize() -> Any? {
-    return map { $0 as Any }
-  }
-}
-
-extension Dictionary : Normalizable {
-  func normalize() -> Any? {
-    var dictionary: [String: Any] = [:]
-
-    for (key, value) in self {
-      if let key = key as? String {
-        dictionary[key] = Stencil.normalize(value)
-      } else if let key = key as? CustomStringConvertible {
-        dictionary[key.description] = Stencil.normalize(value)
-      }
-    }
-
-    return dictionary
-  }
-}
-
-func parseFilterComponents(token: String) -> (String, [Variable]) {
-  var components = token.smartSplit(separator: ":")
-  let name = components.removeFirst()
-  let variables = components
-    .joined(separator: ":")
-    .smartSplit(separator: ",")
-    .map { Variable($0) }
-  return (name, variables)
-}

Stencil.podspec.json

@@ -1,6 +1,6 @@
 {
   "name": "Stencil",
-  "version": "0.10.1",
+  "version": "0.15.1",
   "summary": "Stencil is a simple and powerful template language for Swift.",
   "homepage": "https://stencil.fuller.li",
   "license": {
@@ -12,19 +12,25 @@
   },
   "social_media_url": "https://twitter.com/kylefuller",
   "source": {
-    "git": "https://github.com/kylef/Stencil.git",
+    "git": "https://github.com/stencilproject/Stencil.git",
-    "tag": "0.10.1"
+    "tag": "0.15.1"
   },
   "source_files": [
-    "Sources/*.swift"
+    "Sources/Stencil/*.swift"
   ],
   "platforms": {
     "ios": "8.0",
     "osx": "10.9",
     "tvos": "9.0"
   },
+  "cocoapods_version": ">= 1.7.0",
+  "swift_versions": [
+    "5.0"
+  ],
   "requires_arc": true,
   "dependencies": {
-    "PathKit": [ "~> 0.8.0" ]
+    "PathKit": [
+      "~> 1.0.0"
+    ]
   }
 }

Tests/LinuxMain.swift

@@ -1,3 +0,0 @@
-import StencilTests
-
-stencilTests()

Tests/StencilTests/.swiftlint.yml

@@ -0,0 +1,5 @@
+parent_config: ../../.swiftlint.yml
+
+disabled_rules: # rule identifiers to exclude from running
+  - type_body_length
+  - file_length

Tests/StencilTests/ContextSpec.swift

@@ -1,81 +1,166 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 @testable import Stencil
+import XCTest
 
+final class ContextTests: XCTestCase {
+  func testContextSubscripting() {
+    describe("Context Subscripting") { test in
+      var context = Context()
+      test.before {
+        context = Context(dictionary: ["name": "Kyle"])
+      }
 
-func testContext() {
+      test.it("allows you to get a value via subscripting") {
-  describe("Context") {
-    var context: Context!
-
-    $0.before {
-      context = Context(dictionary: ["name": "Kyle"])
-    }
-
-    $0.it("allows you to get a value via subscripting") {
-      try expect(context["name"] as? String) == "Kyle"
-    }
-
-    $0.it("allows you to set a value via subscripting") {
-      context["name"] = "Katie"
-
-      try expect(context["name"] as? String) == "Katie"
-    }
-
-    $0.it("allows you to remove a value via subscripting") {
-      context["name"] = nil
-
-      try expect(context["name"]).to.beNil()
-    }
-
-    $0.it("allows you to retrieve a value from a parent") {
-      try context.push {
         try expect(context["name"] as? String) == "Kyle"
       }
-    }
 
-    $0.it("allows you to override a parent's value") {
+      test.it("allows you to set a value via subscripting") {
-      try context.push {
         context["name"] = "Katie"
+
         try expect(context["name"] as? String) == "Katie"
       }
-    }
 
-    $0.it("allows you to pop to restore previous state") {
+      test.it("allows you to remove a value via subscripting") {
-      context.push {
-        context["name"] = "Katie"
-      }
-
-      try expect(context["name"] as? String) == "Kyle"
-    }
-
-    $0.it("allows you to remove a parent's value in a level") {
-      try context.push {
         context["name"] = nil
+
         try expect(context["name"]).to.beNil()
       }
 
-      try expect(context["name"] as? String) == "Kyle"
+      test.it("allows you to retrieve a value from a parent") {
-    }
+        try context.push {
-
+          try expect(context["name"] as? String) == "Kyle"
-    $0.it("allows you to push a dictionary and run a closure then restoring previous state") {
+        }
-      var didRun = false
-
-      try context.push(dictionary: ["name": "Katie"]) {
-        didRun = true
-        try expect(context["name"] as? String) == "Katie"
       }
 
-      try expect(didRun).to.beTrue()
+      test.it("allows you to override a parent's value") {
-      try expect(context["name"] as? String) == "Kyle"
+        try context.push {
+          context["name"] = "Katie"
+          try expect(context["name"] as? String) == "Katie"
+        }
+      }
+    }
+  }
+
+  func testContextRestoration() {
+    describe("Context Restoration") { test in
+      var context = Context()
+      test.before {
+        context = Context(dictionary: ["name": "Kyle"])
+      }
+
+      test.it("allows you to pop to restore previous state") {
+        context.push {
+          context["name"] = "Katie"
+        }
+
+        try expect(context["name"] as? String) == "Kyle"
+      }
+
+      test.it("allows you to remove a parent's value in a level") {
+        try context.push {
+          context["name"] = nil
+          try expect(context["name"]).to.beNil()
+        }
+
+        try expect(context["name"] as? String) == "Kyle"
+      }
+
+      test.it("allows you to push a dictionary and run a closure then restoring previous state") {
+        var didRun = false
+
+        try context.push(dictionary: ["name": "Katie"]) {
+          didRun = true
+          try expect(context["name"] as? String) == "Katie"
+        }
+
+        try expect(didRun).to.beTrue()
+        try expect(context["name"] as? String) == "Kyle"
+      }
+
+      test.it("allows you to flatten the context contents") {
+        try context.push(dictionary: ["test": "abc"]) {
+          let flattened = context.flatten()
+
+          try expect(flattened.count) == 2
+          try expect(flattened["name"] as? String) == "Kyle"
+          try expect(flattened["test"] as? String) == "abc"
+        }
+      }
+    }
+  }
+
+  func testContextLazyEvaluation() {
+    let ticker = Ticker()
+    var context = Context()
+    var wrapper = LazyValueWrapper("")
+
+    describe("Lazy evaluation") { test in
+      test.before {
+        ticker.count = 0
+        wrapper = LazyValueWrapper(ticker.tick())
+        context = Context(dictionary: ["name": wrapper])
+      }
+
+      test.it("Evaluates lazy data") {
+        let template = Template(templateString: "{{ name }}")
+        let result = try template.render(context)
+        try expect(result) == "Kyle"
+        try expect(ticker.count) == 1
+      }
+
+      test.it("Evaluates lazy only once") {
+        let template = Template(templateString: "{{ name }}{{ name }}")
+        let result = try template.render(context)
+        try expect(result) == "KyleKyle"
+        try expect(ticker.count) == 1
+      }
+
+      test.it("Does not evaluate lazy data when not used") {
+        let template = Template(templateString: "{{ 'Katie' }}")
+        let result = try template.render(context)
+        try expect(result) == "Katie"
+        try expect(ticker.count) == 0
+      }
+    }
+  }
+
+  func testContextLazyAccessTypes() {
+    it("Supports evaluation via context reference") {
+      let context = Context(dictionary: ["name": "Kyle"])
+      context["alias"] = LazyValueWrapper { $0["name"] ?? "" }
+      let template = Template(templateString: "{{ alias }}")
+
+      try context.push(dictionary: ["name": "Katie"]) {
+        let result = try template.render(context)
+        try expect(result) == "Katie"
+      }
     }
 
-    $0.it("allows you to flatten the context contents") {
+    it("Supports evaluation via context copy") {
-      try context.push(dictionary: ["test": "abc"]) {
+      let context = Context(dictionary: ["name": "Kyle"])
-        let flattened = context.flatten()
+      context["alias"] = LazyValueWrapper(copying: context) { $0["name"] ?? "" }
+      let template = Template(templateString: "{{ alias }}")
 
-        try expect(flattened.count) == 2
+      try context.push(dictionary: ["name": "Katie"]) {
-        try expect(flattened["name"] as? String) == "Kyle"
+        let result = try template.render(context)
-        try expect(flattened["test"] as? String) == "abc"
+        try expect(result) == "Kyle"
       }
     }
   }
 }
+
+// MARK: - Helpers
+
+private final class Ticker {
+  var count: Int = 0
+  func tick() -> String {
+    count += 1
+    return "Kyle"
+  }
+}

Tests/StencilTests/EnvironmentBaseAndChildTemplateSpec.swift

@@ -0,0 +1,131 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import PathKit
+import Spectre
+@testable import Stencil
+import XCTest
+
+final class EnvironmentBaseAndChildTemplateTests: XCTestCase {
+  private var environment = Environment(loader: ExampleLoader())
+  private var childTemplate: Template = ""
+  private var baseTemplate: Template = ""
+
+  override func setUp() {
+    super.setUp()
+
+    let path = Path(#file as String) + ".." + "fixtures"
+    let loader = FileSystemLoader(paths: [path])
+    environment = Environment(loader: loader)
+    childTemplate = ""
+    baseTemplate = ""
+  }
+
+  override func tearDown() {
+    super.tearDown()
+  }
+
+  func testSyntaxErrorInBaseTemplate() throws {
+    childTemplate = try environment.loadTemplate(name: "invalid-child-super.html")
+    baseTemplate = try environment.loadTemplate(name: "invalid-base.html")
+
+    try expectError(
+      reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+      childToken: "extends \"invalid-base.html\"",
+      baseToken: "target|unknown"
+    )
+  }
+
+  func testRuntimeErrorInBaseTemplate() throws {
+    let filterExtension = Extension()
+    filterExtension.registerFilter("unknown") {  (_: Any?) in
+      throw TemplateSyntaxError("filter error")
+    }
+    environment.extensions += [filterExtension]
+
+    childTemplate = try environment.loadTemplate(name: "invalid-child-super.html")
+    baseTemplate = try environment.loadTemplate(name: "invalid-base.html")
+
+    try expectError(
+      reason: "filter error",
+      childToken: "extends \"invalid-base.html\"",
+      baseToken: "target|unknown"
+    )
+  }
+
+  func testSyntaxErrorInChildTemplate() throws {
+    childTemplate = Template(
+      templateString: """
+      {% extends "base.html" %}
+      {% block body %}Child {{ target|unknown }}{% endblock %}
+      """,
+      environment: environment,
+      name: nil
+    )
+
+    try expectError(
+      reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+      childToken: "target|unknown",
+      baseToken: nil
+    )
+  }
+
+  func testRuntimeErrorInChildTemplate() throws {
+    let filterExtension = Extension()
+    filterExtension.registerFilter("unknown") {  (_: Any?) in
+      throw TemplateSyntaxError("filter error")
+    }
+    environment.extensions += [filterExtension]
+
+    childTemplate = Template(
+      templateString: """
+      {% extends "base.html" %}
+      {% block body %}Child {{ target|unknown }}{% endblock %}
+      """,
+      environment: environment,
+      name: nil
+    )
+
+    try expectError(
+      reason: "filter error",
+      childToken: "target|unknown",
+      baseToken: nil
+    )
+  }
+
+  private func expectError(
+    reason: String,
+    childToken: String,
+    baseToken: String?,
+    file: String = #file,
+    line: Int = #line,
+    function: String = #function
+  ) throws {
+    var expectedError = expectedSyntaxError(token: childToken, template: childTemplate, description: reason)
+    if let baseToken = baseToken {
+      expectedError.stackTrace = [
+        expectedSyntaxError(
+          token: baseToken,
+          template: baseTemplate,
+          description: reason
+        ).token
+      ].compactMap { $0 }
+    }
+    let error = try expect(
+      self.environment.render(template: self.childTemplate, context: ["target": "World"]),
+      file: file,
+      line: line,
+      function: function
+    ).toThrow() as TemplateSyntaxError
+    let reporter = SimpleErrorReporter()
+    try expect(
+      reporter.renderError(error),
+      file: file,
+      line: line,
+      function: function
+    ) == reporter.renderError(expectedError)
+  }
+}

Tests/StencilTests/EnvironmentIncludeTemplateSpec.swift

@@ -0,0 +1,94 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import PathKit
+import Spectre
+@testable import Stencil
+import XCTest
+
+final class EnvironmentIncludeTemplateTests: XCTestCase {
+  private var environment = Environment(loader: ExampleLoader())
+  private var template: Template = ""
+  private var includedTemplate: Template = ""
+
+  override func setUp() {
+    super.setUp()
+
+    let path = Path(#file as String) + ".." + "fixtures"
+    let loader = FileSystemLoader(paths: [path])
+    environment = Environment(loader: loader)
+    template = ""
+    includedTemplate = ""
+  }
+
+  override func tearDown() {
+    super.tearDown()
+  }
+
+  func testSyntaxError() throws {
+    template = Template(templateString: """
+      {% include "invalid-include.html" %}
+      """, environment: environment)
+    includedTemplate = try environment.loadTemplate(name: "invalid-include.html")
+
+    try expectError(
+      reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+      token: #"include "invalid-include.html""#,
+      includedToken: "target|unknown"
+    )
+  }
+
+  func testRuntimeError() throws {
+    let filterExtension = Extension()
+    filterExtension.registerFilter("unknown") {  (_: Any?) in
+      throw TemplateSyntaxError("filter error")
+    }
+    environment.extensions += [filterExtension]
+
+    template = Template(templateString: """
+      {% include "invalid-include.html" %}
+      """, environment: environment)
+    includedTemplate = try environment.loadTemplate(name: "invalid-include.html")
+
+    try expectError(
+      reason: "filter error",
+      token: "include \"invalid-include.html\"",
+      includedToken: "target|unknown"
+    )
+  }
+
+  private func expectError(
+    reason: String,
+    token: String,
+    includedToken: String,
+    file: String = #file,
+    line: Int = #line,
+    function: String = #function
+  ) throws {
+    var expectedError = expectedSyntaxError(token: token, template: template, description: reason)
+    expectedError.stackTrace = [
+      expectedSyntaxError(
+        token: includedToken,
+        template: includedTemplate,
+        description: reason
+      ).token
+    ].compactMap { $0 }
+
+    let error = try expect(
+      self.environment.render(template: self.template, context: ["target": "World"]),
+      file: file,
+      line: line,
+      function: function
+    ).toThrow() as TemplateSyntaxError
+    let reporter = SimpleErrorReporter()
+    try expect(
+      reporter.renderError(error),
+      file: file,
+      line: line,
+      function: function
+    ) == reporter.renderError(expectedError)
+  }
+}

Tests/StencilTests/EnvironmentSpec.swift

@@ -1,54 +1,227 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import PathKit
 import Spectre
-import Stencil
+@testable import Stencil
+import XCTest
 
+final class EnvironmentTests: XCTestCase {
+  private var environment = Environment(loader: ExampleLoader())
+  private var template: Template = ""
 
-func testEnvironment() {
+  override func setUp() {
-  describe("Environment") {
+    super.setUp()
-    let environment = Environment(loader: ExampleLoader())
 
-    $0.it("can load a template from a name") {
+    let errorExtension = Extension()
-      let template = try environment.loadTemplate(name: "example.html")
+    errorExtension.registerFilter("throw") { (_: Any?) in
+      throw TemplateSyntaxError("filter error")
+    }
+    errorExtension.registerSimpleTag("simpletag") { _ in
+      throw TemplateSyntaxError("simpletag error")
+    }
+    errorExtension.registerTag("customtag") { _, token in
+      ErrorNode(token: token)
+    }
+
+    environment = Environment(loader: ExampleLoader())
+    environment.extensions += [errorExtension]
+    template = ""
+  }
+
+  override func tearDown() {
+    super.tearDown()
+  }
+
+  func testLoading() {
+    it("can load a template from a name") {
+      let template = try self.environment.loadTemplate(name: "example.html")
       try expect(template.name) == "example.html"
     }
 
-    $0.it("can load a template from a names") {
+    it("can load a template from a names") {
-      let template = try environment.loadTemplate(names: ["first.html", "example.html"])
+      let template = try self.environment.loadTemplate(names: ["first.html", "example.html"])
       try expect(template.name) == "example.html"
     }
+  }
 
-    $0.it("can render a template from a string") {
+  func testRendering() {
-      let result = try environment.renderTemplate(string: "Hello World")
+    it("can render a template from a string") {
+      let result = try self.environment.renderTemplate(string: "Hello World")
       try expect(result) == "Hello World"
     }
 
-    $0.it("can render a template from a file") {
+    it("can render a template from a file") {
-      let result = try environment.renderTemplate(name: "example.html")
+      let result = try self.environment.renderTemplate(name: "example.html")
       try expect(result) == "Hello World!"
     }
 
-    $0.it("allows you to provide a custom template class") {
+    it("allows you to provide a custom template class") {
       let environment = Environment(loader: ExampleLoader(), templateClass: CustomTemplate.self)
       let result = try environment.renderTemplate(string: "Hello World")
 
       try expect(result) == "here"
     }
   }
-}
 
-
+  func testSyntaxError() {
-fileprivate class ExampleLoader: Loader {
+    it("reports syntax error on invalid for tag syntax") {
-  func loadTemplate(name: String, environment: Environment) throws -> Template {
+      self.template = "Hello {% for name in %}{{ name }}, {% endfor %}!"
-    if name == "example.html" {
+      try self.expectError(
-      return Template(templateString: "Hello World!", environment: environment, name: name)
+        reason: "'for' statements should use the syntax: `for <x> in <y> [where <condition>]`.",
+        token: "for name in"
+      )
     }
 
-    throw TemplateDoesNotExist(templateNames: [name], loader: self)
+    it("reports syntax error on missing endfor") {
+      self.template = "{% for name in names %}{{ name }}"
+      try self.expectError(reason: "`endfor` was not found.", token: "for name in names")
+    }
+
+    it("reports syntax error on unknown tag") {
+      self.template = "{% for name in names %}{{ name }}{% end %}"
+      try self.expectError(reason: "Unknown template tag 'end'", token: "end")
+    }
+  }
+
+  func testUnknownFilter() {
+    it("reports syntax error in for tag") {
+      self.template = "{% for name in names|unknown %}{{ name }}{% endfor %}"
+      try self.expectError(
+        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        token: "names|unknown"
+      )
+    }
+
+    it("reports syntax error in for-where tag") {
+      self.template = "{% for name in names where name|unknown %}{{ name }}{% endfor %}"
+      try self.expectError(
+        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        token: "name|unknown"
+      )
+    }
+
+    it("reports syntax error in if tag") {
+      self.template = "{% if name|unknown %}{{ name }}{% endif %}"
+      try self.expectError(
+        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        token: "name|unknown"
+      )
+    }
+
+    it("reports syntax error in elif tag") {
+      self.template = "{% if name %}{{ name }}{% elif name|unknown %}{% endif %}"
+      try self.expectError(
+        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        token: "name|unknown"
+      )
+    }
+
+    it("reports syntax error in ifnot tag") {
+      self.template = "{% ifnot name|unknown %}{{ name }}{% endif %}"
+      try self.expectError(
+        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        token: "name|unknown"
+      )
+    }
+
+    it("reports syntax error in filter tag") {
+      self.template = "{% filter unknown %}Text{% endfilter %}"
+      try self.expectError(
+        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        token: "filter unknown"
+      )
+    }
+
+    it("reports syntax error in variable tag") {
+      self.template = "{{ name|unknown }}"
+      try self.expectError(
+        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        token: "name|unknown"
+      )
+    }
+
+    it("reports error in variable tag") {
+      self.template = "{{ }}"
+      try self.expectError(reason: "Missing variable name", token: " ")
+    }
+  }
+
+  func testRenderingError() {
+    it("reports rendering error in variable filter") {
+      self.template = Template(templateString: "{{ name|throw }}", environment: self.environment)
+      try self.expectError(reason: "filter error", token: "name|throw")
+    }
+
+    it("reports rendering error in filter tag") {
+      self.template = Template(templateString: "{% filter throw %}Test{% endfilter %}", environment: self.environment)
+      try self.expectError(reason: "filter error", token: "filter throw")
+    }
+
+    it("reports rendering error in simple tag") {
+      self.template = Template(templateString: "{% simpletag %}", environment: self.environment)
+      try self.expectError(reason: "simpletag error", token: "simpletag")
+    }
+
+    it("reports passing argument to simple filter") {
+      self.template = "{{ name|uppercase:5 }}"
+      try self.expectError(reason: "Can't invoke filter with an argument", token: "name|uppercase:5")
+    }
+
+    it("reports rendering error in custom tag") {
+      self.template = Template(templateString: "{% customtag %}", environment: self.environment)
+      try self.expectError(reason: "Custom Error", token: "customtag")
+    }
+
+    it("reports rendering error in for body") {
+      self.template = Template(templateString: """
+        {% for name in names %}{% customtag %}{% endfor %}
+        """, environment: self.environment)
+      try self.expectError(reason: "Custom Error", token: "customtag")
+    }
+
+    it("reports rendering error in block") {
+      self.template = Template(
+        templateString: "{% block some %}{% customtag %}{% endblock %}",
+        environment: self.environment
+      )
+      try self.expectError(reason: "Custom Error", token: "customtag")
+    }
+  }
+
+  private func expectError(
+    reason: String,
+    token: String,
+    file: String = #file,
+    line: Int = #line,
+    function: String = #function
+  ) throws {
+    let expectedError = expectedSyntaxError(token: token, template: template, description: reason)
+
+    let error = try expect(
+      self.environment.render(template: self.template, context: ["names": ["Bob", "Alice"], "name": "Bob"]),
+      file: file,
+      line: line,
+      function: function
+    ).toThrow() as TemplateSyntaxError
+    let reporter = SimpleErrorReporter()
+    try expect(
+      reporter.renderError(error),
+      file: file,
+      line: line,
+      function: function
+    ) == reporter.renderError(expectedError)
   }
 }
 
+// MARK: - Helpers
 
-class CustomTemplate: Template {
+private class CustomTemplate: Template {
+  // swiftlint:disable discouraged_optional_collection
   override func render(_ dictionary: [String: Any]? = nil) throws -> String {
-    return "here"
+    "here"
   }
 }

Tests/StencilTests/ExpressionSpec.swift

@@ -1,300 +1,361 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 @testable import Stencil
+import XCTest
 
+final class ExpressionsTests: XCTestCase {
+  private let parser = TokenParser(tokens: [], environment: Environment())
 
-func testExpressions() {
+  private func makeExpression(_ components: [String]) -> Expression {
-  describe("Expression") {
+    do {
-    let parser = TokenParser(tokens: [], environment: Environment())
+      let parser = try IfExpressionParser.parser(
-
+        components: components,
-    $0.describe("VariableExpression") {
+        environment: Environment(),
-      let expression = VariableExpression(variable: Variable("value"))
+        token: .text(value: "", at: .unknown)
-
+      )
-      $0.it("evaluates to true when value is not nil") {
+      return try parser.parse()
-        let context = Context(dictionary: ["value": "known"])
+    } catch {
-        try expect(try expression.evaluate(context: context)).to.beTrue()
+      fatalError(error.localizedDescription)
-      }
-
-      $0.it("evaluates to false when value is unset") {
-        let context = Context()
-        try expect(try expression.evaluate(context: context)).to.beFalse()
-      }
-
-      $0.it("evaluates to true when array variable is not empty") {
-        let items: [[String: Any]] = [["key":"key1","value":42],["key":"key2","value":1337]]
-        let context = Context(dictionary: ["value": [items]])
-        try expect(try expression.evaluate(context: context)).to.beTrue()
-      }
-
-      $0.it("evaluates to false when array value is empty") {
-        let emptyItems = [[String: Any]]()
-        let context = Context(dictionary: ["value": emptyItems])
-        try expect(try expression.evaluate(context: context)).to.beFalse()
-      }
-
-      $0.it("evaluates to false when dictionary value is empty") {
-        let emptyItems = [String:Any]()
-        let context = Context(dictionary: ["value": emptyItems])
-        try expect(try expression.evaluate(context: context)).to.beFalse()
-      }
-
-      $0.it("evaluates to false when Array<Any> value is empty") {
-        let context = Context(dictionary: ["value": ([] as [Any])])
-        try expect(try expression.evaluate(context: context)).to.beFalse()
-      }
-
-      $0.it("evaluates to true when integer value is above 0") {
-        let context = Context(dictionary: ["value": 1])
-        try expect(try expression.evaluate(context: context)).to.beTrue()
-      }
-
-      $0.it("evaluates to true with string") {
-        let context = Context(dictionary: ["value": "test"])
-        try expect(try expression.evaluate(context: context)).to.beTrue()
-      }
-
-      $0.it("evaluates to false when empty string") {
-        let context = Context(dictionary: ["value": ""])
-        try expect(try expression.evaluate(context: context)).to.beFalse()
-      }
-
-      $0.it("evaluates to false when integer value is below 0 or below") {
-        let context = Context(dictionary: ["value": 0])
-        try expect(try expression.evaluate(context: context)).to.beFalse()
-
-        let negativeContext = Context(dictionary: ["value": 0])
-        try expect(try expression.evaluate(context: negativeContext)).to.beFalse()
-      }
-
-      $0.it("evaluates to true when float value is above 0") {
-        let context = Context(dictionary: ["value": Float(0.5)])
-        try expect(try expression.evaluate(context: context)).to.beTrue()
-      }
-
-      $0.it("evaluates to false when float is 0 or below") {
-        let context = Context(dictionary: ["value": Float(0)])
-        try expect(try expression.evaluate(context: context)).to.beFalse()
-      }
-
-      $0.it("evaluates to true when double value is above 0") {
-        let context = Context(dictionary: ["value": Double(0.5)])
-        try expect(try expression.evaluate(context: context)).to.beTrue()
-      }
-
-      $0.it("evaluates to false when double is 0 or below") {
-        let context = Context(dictionary: ["value": Double(0)])
-        try expect(try expression.evaluate(context: context)).to.beFalse()
-      }
-
-      $0.it("evaluates to false when uint is 0") {
-        let context = Context(dictionary: ["value": UInt(0)])
-        try expect(try expression.evaluate(context: context)).to.beFalse()
-      }
-    }
-
-    $0.describe("NotExpression") {
-      $0.it("returns truthy for positive expressions") {
-        let expression = NotExpression(expression: StaticExpression(value: true))
-        try expect(expression.evaluate(context: Context())).to.beFalse()
-      }
-
-      $0.it("returns falsy for negative expressions") {
-        let expression = NotExpression(expression: StaticExpression(value: false))
-        try expect(expression.evaluate(context: Context())).to.beTrue()
-      }
-    }
-
-    $0.describe("expression parsing") {
-      $0.it("can parse a variable expression") {
-        let expression = try parseExpression(components: ["value"], tokenParser: parser)
-        try expect(expression.evaluate(context: Context())).to.beFalse()
-        try expect(expression.evaluate(context: Context(dictionary: ["value": true]))).to.beTrue()
-      }
-
-      $0.it("can parse a not expression") {
-        let expression = try parseExpression(components: ["not", "value"], tokenParser: parser)
-        try expect(expression.evaluate(context: Context())).to.beTrue()
-        try expect(expression.evaluate(context: Context(dictionary: ["value": true]))).to.beFalse()
-      }
-
-      $0.describe("and expression") {
-        let expression = try! parseExpression(components: ["lhs", "and", "rhs"], tokenParser: parser)
-
-        $0.it("evaluates to false with lhs false") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": false, "rhs": true]))).to.beFalse()
-        }
-
-        $0.it("evaluates to false with rhs false") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": false]))).to.beFalse()
-        }
-
-        $0.it("evaluates to false with lhs and rhs false") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": false, "rhs": false]))).to.beFalse()
-        }
-
-        $0.it("evaluates to true with lhs and rhs true") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": true]))).to.beTrue()
-        }
-      }
-
-      $0.describe("or expression") {
-        let expression = try! parseExpression(components: ["lhs", "or", "rhs"], tokenParser: parser)
-
-        $0.it("evaluates to true with lhs true") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": false]))).to.beTrue()
-        }
-
-        $0.it("evaluates to true with rhs true") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": false, "rhs": true]))).to.beTrue()
-        }
-
-        $0.it("evaluates to true with lhs and rhs true") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": true]))).to.beTrue()
-        }
-
-        $0.it("evaluates to false with lhs and rhs false") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": false, "rhs": false]))).to.beFalse()
-        }
-      }
-
-      $0.describe("equality expression") {
-        let expression = try! parseExpression(components: ["lhs", "==", "rhs"], tokenParser: parser)
-
-        $0.it("evaluates to true with equal lhs/rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": "a"]))).to.beTrue()
-        }
-
-        $0.it("evaluates to false with non equal lhs/rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": "b"]))).to.beFalse()
-        }
-
-        $0.it("evaluates to true with nils") {
-          try expect(expression.evaluate(context: Context(dictionary: [:]))).to.beTrue()
-        }
-
-        $0.it("evaluates to true with numbers") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 1, "rhs": 1.0]))).to.beTrue()
-        }
-
-        $0.it("evaluates to false with non equal numbers") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 1, "rhs": 1.1]))).to.beFalse()
-        }
-
-        $0.it("evaluates to true with booleans") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": true]))).to.beTrue()
-        }
-
-        $0.it("evaluates to false with falsy booleans") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": false]))).to.beFalse()
-        }
-
-        $0.it("evaluates to false with different types") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": 1]))).to.beFalse()
-        }
-      }
-
-      $0.describe("inequality expression") {
-        let expression = try! parseExpression(components: ["lhs", "!=", "rhs"], tokenParser: parser)
-
-        $0.it("evaluates to true with inequal lhs/rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": "b"]))).to.beTrue()
-        }
-
-        $0.it("evaluates to false with equal lhs/rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": "b", "rhs": "b"]))).to.beFalse()
-        }
-      }
-
-      $0.describe("more than expression") {
-        let expression = try! parseExpression(components: ["lhs", ">", "rhs"], tokenParser: parser)
-
-        $0.it("evaluates to true with lhs > rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 4]))).to.beTrue()
-        }
-
-        $0.it("evaluates to false with lhs == rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5.0]))).to.beFalse()
-        }
-      }
-
-      $0.describe("more than equal expression") {
-        let expression = try! parseExpression(components: ["lhs", ">=", "rhs"], tokenParser: parser)
-
-        $0.it("evaluates to true with lhs == rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5]))).to.beTrue()
-        }
-
-        $0.it("evaluates to false with lhs < rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5.1]))).to.beFalse()
-        }
-      }
-
-      $0.describe("less than expression") {
-        let expression = try! parseExpression(components: ["lhs", "<", "rhs"], tokenParser: parser)
-
-        $0.it("evaluates to true with lhs < rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 4, "rhs": 4.5]))).to.beTrue()
-        }
-
-        $0.it("evaluates to false with lhs == rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5.0]))).to.beFalse()
-        }
-      }
-
-      $0.describe("less than equal expression") {
-        let expression = try! parseExpression(components: ["lhs", "<=", "rhs"], tokenParser: parser)
-
-        $0.it("evaluates to true with lhs == rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5]))).to.beTrue()
-        }
-
-        $0.it("evaluates to false with lhs > rhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.1, "rhs": 5.0]))).to.beFalse()
-        }
-      }
-
-      $0.describe("multiple expression") {
-        let expression = try! parseExpression(components: ["one", "or", "two", "and", "not", "three"], tokenParser: parser)
-
-        $0.it("evaluates to true with one") {
-          try expect(expression.evaluate(context: Context(dictionary: ["one": true]))).to.beTrue()
-        }
-
-        $0.it("evaluates to true with one and three") {
-          try expect(expression.evaluate(context: Context(dictionary: ["one": true, "three": true]))).to.beTrue()
-        }
-
-        $0.it("evaluates to true with two") {
-          try expect(expression.evaluate(context: Context(dictionary: ["two": true]))).to.beTrue()
-        }
-
-        $0.it("evaluates to false with two and three") {
-          try expect(expression.evaluate(context: Context(dictionary: ["two": true, "three": true]))).to.beFalse()
-        }
-
-        $0.it("evaluates to false with two and three") {
-          try expect(expression.evaluate(context: Context(dictionary: ["two": true, "three": true]))).to.beFalse()
-        }
-
-        $0.it("evaluates to false with nothing") {
-          try expect(expression.evaluate(context: Context())).to.beFalse()
-        }
-      }
-      
-      $0.describe("in expression") {
-        let expression = try! parseExpression(components: ["lhs", "in", "rhs"], tokenParser: parser)
-        
-        $0.it("evaluates to true when rhs contains lhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 1, "rhs": [1, 2, 3]]))).to.beTrue()
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": ["a", "b", "c"]]))).to.beTrue()
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": "abc"]))).to.beTrue()
-        }
-        
-        $0.it("evaluates to false when rhs does not contain lhs") {
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": 1, "rhs": [2, 3, 4]]))).to.beFalse()
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": ["b", "c", "d"]]))).to.beFalse()
-          try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": "bcd"]))).to.beFalse()
-        }
-      }
     }
   }
+
+  func testTrueExpressions() {
+    let expression = VariableExpression(variable: Variable("value"))
+
+    it("evaluates to true when value is not nil") {
+      let context = Context(dictionary: ["value": "known"])
+      try expect(try expression.evaluate(context: context)).to.beTrue()
+    }
+
+    it("evaluates to true when array variable is not empty") {
+      let items: [[String: Any]] = [["key": "key1", "value": 42], ["key": "key2", "value": 1_337]]
+      let context = Context(dictionary: ["value": [items]])
+      try expect(try expression.evaluate(context: context)).to.beTrue()
+    }
+
+    it("evaluates to false when dictionary value is empty") {
+      let emptyItems = [String: Any]()
+      let context = Context(dictionary: ["value": emptyItems])
+      try expect(try expression.evaluate(context: context)).to.beFalse()
+    }
+
+    it("evaluates to true when integer value is above 0") {
+      let context = Context(dictionary: ["value": 1])
+      try expect(try expression.evaluate(context: context)).to.beTrue()
+    }
+
+    it("evaluates to true with string") {
+      let context = Context(dictionary: ["value": "test"])
+      try expect(try expression.evaluate(context: context)).to.beTrue()
+    }
+
+    it("evaluates to true when float value is above 0") {
+      let context = Context(dictionary: ["value": Float(0.5)])
+      try expect(try expression.evaluate(context: context)).to.beTrue()
+    }
+
+    it("evaluates to true when double value is above 0") {
+      let context = Context(dictionary: ["value": Double(0.5)])
+      try expect(try expression.evaluate(context: context)).to.beTrue()
+    }
+  }
+
+  func testFalseExpressions() {
+    let expression = VariableExpression(variable: Variable("value"))
+
+    it("evaluates to false when value is unset") {
+      let context = Context()
+      try expect(try expression.evaluate(context: context)).to.beFalse()
+    }
+
+    it("evaluates to false when array value is empty") {
+      let emptyItems = [[String: Any]]()
+      let context = Context(dictionary: ["value": emptyItems])
+      try expect(try expression.evaluate(context: context)).to.beFalse()
+    }
+
+    it("evaluates to false when dictionary value is empty") {
+      let emptyItems = [String: Any]()
+      let context = Context(dictionary: ["value": emptyItems])
+      try expect(try expression.evaluate(context: context)).to.beFalse()
+    }
+
+    it("evaluates to false when Array<Any> value is empty") {
+      let context = Context(dictionary: ["value": ([] as [Any])])
+      try expect(try expression.evaluate(context: context)).to.beFalse()
+    }
+
+    it("evaluates to false when empty string") {
+      let context = Context(dictionary: ["value": ""])
+      try expect(try expression.evaluate(context: context)).to.beFalse()
+    }
+
+    it("evaluates to false when integer value is below 0 or below") {
+      let context = Context(dictionary: ["value": 0])
+      try expect(try expression.evaluate(context: context)).to.beFalse()
+
+      let negativeContext = Context(dictionary: ["value": -1])
+      try expect(try expression.evaluate(context: negativeContext)).to.beFalse()
+    }
+
+    it("evaluates to false when float is 0 or below") {
+      let context = Context(dictionary: ["value": Float(0)])
+      try expect(try expression.evaluate(context: context)).to.beFalse()
+    }
+
+    it("evaluates to false when double is 0 or below") {
+      let context = Context(dictionary: ["value": Double(0)])
+      try expect(try expression.evaluate(context: context)).to.beFalse()
+    }
+
+    it("evaluates to false when uint is 0") {
+      let context = Context(dictionary: ["value": UInt(0)])
+      try expect(try expression.evaluate(context: context)).to.beFalse()
+    }
+  }
+
+  func testNotExpression() {
+    it("returns truthy for positive expressions") {
+      let expression = NotExpression(expression: VariableExpression(variable: Variable("true")))
+      try expect(expression.evaluate(context: Context())).to.beFalse()
+    }
+
+    it("returns falsy for negative expressions") {
+      let expression = NotExpression(expression: VariableExpression(variable: Variable("false")))
+      try expect(expression.evaluate(context: Context())).to.beTrue()
+    }
+  }
+
+  func testExpressionParsing() {
+    it("can parse a variable expression") {
+      let expression = self.makeExpression(["value"])
+      try expect(expression.evaluate(context: Context())).to.beFalse()
+      try expect(expression.evaluate(context: Context(dictionary: ["value": true]))).to.beTrue()
+    }
+
+    it("can parse a not expression") {
+      let expression = self.makeExpression(["not", "value"])
+      try expect(expression.evaluate(context: Context())).to.beTrue()
+      try expect(expression.evaluate(context: Context(dictionary: ["value": true]))).to.beFalse()
+    }
+  }
+
+  func testAndExpression() {
+    let expression = makeExpression(["lhs", "and", "rhs"])
+
+    it("evaluates to false with lhs false") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": false, "rhs": true]))).to.beFalse()
+    }
+
+    it("evaluates to false with rhs false") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": false]))).to.beFalse()
+    }
+
+    it("evaluates to false with lhs and rhs false") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": false, "rhs": false]))).to.beFalse()
+    }
+
+    it("evaluates to true with lhs and rhs true") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": true]))).to.beTrue()
+    }
+  }
+
+  func testOrExpression() {
+    let expression = makeExpression(["lhs", "or", "rhs"])
+
+    it("evaluates to true with lhs true") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": false]))).to.beTrue()
+    }
+
+    it("evaluates to true with rhs true") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": false, "rhs": true]))).to.beTrue()
+    }
+
+    it("evaluates to true with lhs and rhs true") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": true]))).to.beTrue()
+    }
+
+    it("evaluates to false with lhs and rhs false") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": false, "rhs": false]))).to.beFalse()
+    }
+  }
+
+  func testEqualityExpression() {
+    let expression = makeExpression(["lhs", "==", "rhs"])
+
+    it("evaluates to true with equal lhs/rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": "a"]))).to.beTrue()
+    }
+
+    it("evaluates to false with non equal lhs/rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": "b"]))).to.beFalse()
+    }
+
+    it("evaluates to true with nils") {
+      try expect(expression.evaluate(context: Context(dictionary: [:]))).to.beTrue()
+    }
+
+    it("evaluates to true with numbers") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": 1, "rhs": 1.0]))).to.beTrue()
+    }
+
+    it("evaluates to false with non equal numbers") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": 1, "rhs": 1.1]))).to.beFalse()
+    }
+
+    it("evaluates to true with booleans") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": true]))).to.beTrue()
+    }
+
+    it("evaluates to false with falsy booleans") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": false]))).to.beFalse()
+    }
+
+    it("evaluates to false with different types") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": true, "rhs": 1]))).to.beFalse()
+    }
+  }
+
+  func testInequalityExpression() {
+    let expression = makeExpression(["lhs", "!=", "rhs"])
+
+    it("evaluates to true with inequal lhs/rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": "a", "rhs": "b"]))).to.beTrue()
+    }
+
+    it("evaluates to false with equal lhs/rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": "b", "rhs": "b"]))).to.beFalse()
+    }
+  }
+
+  func testMoreThanExpression() {
+    let expression = makeExpression(["lhs", ">", "rhs"])
+
+    it("evaluates to true with lhs > rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 4]))).to.beTrue()
+    }
+
+    it("evaluates to false with lhs == rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5.0]))).to.beFalse()
+    }
+  }
+
+  func testMoreThanEqualExpression() {
+    let expression = makeExpression(["lhs", ">=", "rhs"])
+
+    it("evaluates to true with lhs == rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5]))).to.beTrue()
+    }
+
+    it("evaluates to false with lhs < rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5.1]))).to.beFalse()
+    }
+  }
+
+  func testLessThanExpression() {
+    let expression = makeExpression(["lhs", "<", "rhs"])
+
+    it("evaluates to true with lhs < rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": 4, "rhs": 4.5]))).to.beTrue()
+    }
+
+    it("evaluates to false with lhs == rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5.0]))).to.beFalse()
+    }
+  }
+
+  func testLessThanEqualExpression() {
+    let expression = makeExpression(["lhs", "<=", "rhs"])
+
+    it("evaluates to true with lhs == rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.0, "rhs": 5]))).to.beTrue()
+    }
+
+    it("evaluates to false with lhs > rhs") {
+      try expect(expression.evaluate(context: Context(dictionary: ["lhs": 5.1, "rhs": 5.0]))).to.beFalse()
+    }
+  }
+
+  func testMultipleExpressions() {
+    let expression = makeExpression(["one", "or", "two", "and", "not", "three"])
+
+    it("evaluates to true with one") {
+      try expect(expression.evaluate(context: Context(dictionary: ["one": true]))).to.beTrue()
+    }
+
+    it("evaluates to true with one and three") {
+      try expect(expression.evaluate(context: Context(dictionary: ["one": true, "three": true]))).to.beTrue()
+    }
+
+    it("evaluates to true with two") {
+      try expect(expression.evaluate(context: Context(dictionary: ["two": true]))).to.beTrue()
+    }
+
+    it("evaluates to false with two and three") {
+      try expect(expression.evaluate(context: Context(dictionary: ["two": true, "three": true]))).to.beFalse()
+    }
+
+    it("evaluates to false with two and three") {
+      try expect(expression.evaluate(context: Context(dictionary: ["two": true, "three": true]))).to.beFalse()
+    }
+
+    it("evaluates to false with nothing") {
+      try expect(expression.evaluate(context: Context())).to.beFalse()
+    }
+  }
+
+  func testTrueInExpression() throws {
+    let expression = makeExpression(["lhs", "in", "rhs"])
+
+    try expect(expression.evaluate(context: Context(dictionary: [
+      "lhs": 1,
+      "rhs": [1, 2, 3]
+    ]))).to.beTrue()
+    try expect(expression.evaluate(context: Context(dictionary: [
+      "lhs": "a",
+      "rhs": ["a", "b", "c"]
+    ]))).to.beTrue()
+    try expect(expression.evaluate(context: Context(dictionary: [
+      "lhs": "a",
+      "rhs": "abc"
+    ]))).to.beTrue()
+    try expect(expression.evaluate(context: Context(dictionary: [
+      "lhs": 1,
+      "rhs": 1...3
+    ]))).to.beTrue()
+    try expect(expression.evaluate(context: Context(dictionary: [
+      "lhs": 1,
+      "rhs": 1..<3
+    ]))).to.beTrue()
+  }
+
+  func testFalseInExpression() throws {
+    let expression = makeExpression(["lhs", "in", "rhs"])
+
+    try expect(expression.evaluate(context: Context(dictionary: [
+      "lhs": 1,
+      "rhs": [2, 3, 4]
+    ]))).to.beFalse()
+    try expect(expression.evaluate(context: Context(dictionary: [
+      "lhs": "a",
+      "rhs": ["b", "c", "d"]
+    ]))).to.beFalse()
+    try expect(expression.evaluate(context: Context(dictionary: [
+      "lhs": "a",
+      "rhs": "bcd"
+    ]))).to.beFalse()
+    try expect(expression.evaluate(context: Context(dictionary: [
+      "lhs": 4,
+      "rhs": 1...3
+    ]))).to.beFalse()
+    try expect(expression.evaluate(context: Context(dictionary: [
+      "lhs": 3,
+      "rhs": 1..<3
+    ]))).to.beFalse()
+  }
 }

Tests/StencilTests/FilterSpec.swift

@@ -1,12 +1,18 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 @testable import Stencil
+import XCTest
 
-
+final class FilterTests: XCTestCase {
-func testFilter() {
+  func testRegistration() {
-  describe("template filters") {
     let context: [String: Any] = ["name": "Kyle"]
 
-    $0.it("allows you to register a custom filter") {
+    it("allows you to register a custom filter") {
       let template = Template(templateString: "{{ name|repeat }}")
 
       let repeatExtension = Extension()
@@ -18,149 +24,440 @@ func testFilter() {
         return nil
       }
 
-      let result = try template.render(Context(dictionary: context, environment: Environment(extensions: [repeatExtension])))
+      let result = try template.render(Context(
+        dictionary: context,
+        environment: Environment(extensions: [repeatExtension])
+      ))
       try expect(result) == "Kyle Kyle"
     }
 
-    $0.it("allows you to register a custom filter which accepts single argument") {
+    it("allows you to register boolean filters") {
-      let template = Template(templateString: "{{ name|repeat:'value1, \"value2\"' }}")
-
       let repeatExtension = Extension()
-      repeatExtension.registerFilter("repeat") { value, arguments in
+      repeatExtension.registerFilter(name: "isPositive", negativeFilterName: "isNotPositive") { (value: Any?) in
-        if !arguments.isEmpty {
+        if let value = value as? Int {
-          return "\(value!) \(value!) with args \(arguments.first!!)"
+          return value > 0
         }
-
         return nil
       }
 
-      let result = try template.render(Context(dictionary: context, environment: Environment(extensions: [repeatExtension])))
+      let result = try Template(templateString: "{{ value|isPositive }}")
-      try expect(result) == "Kyle Kyle with args value1, \"value2\""
+        .render(Context(dictionary: ["value": 1], environment: Environment(extensions: [repeatExtension])))
+      try expect(result) == "true"
+
+      let negativeResult = try Template(templateString: "{{ value|isNotPositive }}")
+        .render(Context(dictionary: ["value": -1], environment: Environment(extensions: [repeatExtension])))
+      try expect(negativeResult) == "true"
     }
 
-    $0.it("allows you to register a custom filter which accepts several arguments") {
+    it("allows you to register a custom which throws") {
-        let template = Template(templateString: "{{ name|repeat:'value\"1\"',\"value'2'\",'(key, value)' }}")
-
-        let repeatExtension = Extension()
-        repeatExtension.registerFilter("repeat") { value, arguments in
-            if !arguments.isEmpty {
-                return "\(value!) \(value!) with args 0: \(arguments[0]!), 1: \(arguments[1]!), 2: \(arguments[2]!)"
-            }
-
-            return nil
-        }
-
-        let result = try template.render(Context(dictionary: context, environment: Environment(extensions: [repeatExtension])))
-        try expect(result) == "Kyle Kyle with args 0: value\"1\", 1: value'2', 2: (key, value)"
-    }
-
-    $0.it("allows you to register a custom which throws") {
       let template = Template(templateString: "{{ name|repeat }}")
       let repeatExtension = Extension()
-      repeatExtension.registerFilter("repeat") { (value: Any?) in
+      repeatExtension.registerFilter("repeat") { (_: Any?) in
         throw TemplateSyntaxError("No Repeat")
       }
 
       let context = Context(dictionary: context, environment: Environment(extensions: [repeatExtension]))
-      try expect(try template.render(context)).toThrow(TemplateSyntaxError("No Repeat"))
+      try expect(try template.render(context))
+        .toThrow(TemplateSyntaxError(reason: "No Repeat", token: template.tokens.first))
     }
 
-    $0.it("allows you to override a default filter") {
+    it("throws when you pass arguments to simple filter") {
-      let template = Template(templateString: "{{ name|join }}")
-
-      let repeatExtension = Extension()
-      repeatExtension.registerFilter("join") { (value: Any?) in
-        return "joined"
-      }
-
-      let result = try template.render(Context(dictionary: context, environment: Environment(extensions: [repeatExtension])))
-      try expect(result) == "joined"
-    }
-
-    $0.it("allows whitespace in expression") {
-      let template = Template(templateString: "{{ name | uppercase }}")
-      let result = try template.render(Context(dictionary: ["name": "kyle"]))
-      try expect(result) == "KYLE"
-    }
-
-    $0.it("throws when you pass arguments to simple filter") {
       let template = Template(templateString: "{{ name|uppercase:5 }}")
       try expect(try template.render(Context(dictionary: ["name": "kyle"]))).toThrow()
     }
   }
 
+  func testRegistrationOverrideDefault() throws {
+    let template = Template(templateString: "{{ name|join }}")
+    let context: [String: Any] = ["name": "Kyle"]
 
-  describe("capitalize filter") {
+    let repeatExtension = Extension()
-    let template = Template(templateString: "{{ name|capitalize }}")
+    repeatExtension.registerFilter("join") { (_: Any?) in
+      "joined"
+    }
 
-    $0.it("capitalizes a string") {
+    let result = try template.render(Context(
+      dictionary: context,
+      environment: Environment(extensions: [repeatExtension])
+    ))
+    try expect(result) == "joined"
+  }
+
+  func testRegistrationWithArguments() {
+    let context: [String: Any] = ["name": "Kyle"]
+
+    it("allows you to register a custom filter which accepts single argument") {
+      let template = Template(templateString: """
+        {{ name|repeat:'value1, "value2"' }}
+        """)
+
+      let repeatExtension = Extension()
+      repeatExtension.registerFilter("repeat") { value, arguments in
+        guard let value = value,
+          let argument = arguments.first else { return nil }
+
+        return "\(value) \(value) with args \(argument ?? "")"
+      }
+
+      let result = try template.render(Context(
+        dictionary: context,
+        environment: Environment(extensions: [repeatExtension])
+      ))
+      try expect(result) == """
+        Kyle Kyle with args value1, "value2"
+        """
+    }
+
+    it("allows you to register a custom filter which accepts several arguments") {
+      let template = Template(templateString: """
+        {{ name|repeat:'value"1"',"value'2'",'(key, value)' }}
+        """)
+
+      let repeatExtension = Extension()
+      repeatExtension.registerFilter("repeat") { value, arguments in
+        guard let value = value else { return nil }
+        let args = arguments.compactMap { $0 }
+        return "\(value) \(value) with args 0: \(args[0]), 1: \(args[1]), 2: \(args[2])"
+      }
+
+      let result = try template.render(Context(
+        dictionary: context,
+        environment: Environment(extensions: [repeatExtension])
+      ))
+      try expect(result) == """
+        Kyle Kyle with args 0: value"1", 1: value'2', 2: (key, value)
+        """
+    }
+
+    it("allows whitespace in expression") {
+      let template = Template(templateString: """
+        {{ value | join : ", " }}
+        """)
+      let result = try template.render(Context(dictionary: ["value": ["One", "Two"]]))
+      try expect(result) == "One, Two"
+    }
+  }
+
+  func testStringFilters() {
+    it("transforms a string to be capitalized") {
+      let template = Template(templateString: "{{ name|capitalize }}")
       let result = try template.render(Context(dictionary: ["name": "kyle"]))
       try expect(result) == "Kyle"
     }
-  }
 
-
+    it("transforms a string to be uppercase") {
-  describe("uppercase filter") {
+      let template = Template(templateString: "{{ name|uppercase }}")
-    let template = Template(templateString: "{{ name|uppercase }}")
-
-    $0.it("transforms a string to be uppercase") {
       let result = try template.render(Context(dictionary: ["name": "kyle"]))
       try expect(result) == "KYLE"
     }
-  }
 
-  describe("lowercase filter") {
+    it("transforms a string to be lowercase") {
-    let template = Template(templateString: "{{ name|lowercase }}")
+      let template = Template(templateString: "{{ name|lowercase }}")
-
-    $0.it("transforms a string to be lowercase") {
       let result = try template.render(Context(dictionary: ["name": "Kyle"]))
       try expect(result) == "kyle"
     }
   }
 
-  describe("default filter") {
+  func testStringFiltersWithArrays() {
-    let template = Template(templateString: "Hello {{ name|default:\"World\" }}")
+    it("transforms a string to be capitalized") {
+      let template = Template(templateString: "{{ names|capitalize }}")
+      let result = try template.render(Context(dictionary: ["names": ["kyle", "kyle"]]))
+      try expect(result) == """
+        ["Kyle", "Kyle"]
+        """
+    }
 
-    $0.it("shows the variable value") {
+    it("transforms a string to be uppercase") {
+      let template = Template(templateString: "{{ names|uppercase }}")
+      let result = try template.render(Context(dictionary: ["names": ["kyle", "kyle"]]))
+      try expect(result) == """
+        ["KYLE", "KYLE"]
+        """
+    }
+
+    it("transforms a string to be lowercase") {
+      let template = Template(templateString: "{{ names|lowercase }}")
+      let result = try template.render(Context(dictionary: ["names": ["Kyle", "Kyle"]]))
+      try expect(result) == """
+        ["kyle", "kyle"]
+        """
+    }
+  }
+
+  func testDefaultFilter() {
+    let template = Template(templateString: """
+      Hello {{ name|default:"World" }}
+      """)
+
+    it("shows the variable value") {
       let result = try template.render(Context(dictionary: ["name": "Kyle"]))
       try expect(result) == "Hello Kyle"
     }
 
-    $0.it("shows the default value") {
+    it("shows the default value") {
       let result = try template.render(Context(dictionary: [:]))
       try expect(result) == "Hello World"
     }
 
-    $0.it("supports multiple defaults") {
+    it("supports multiple defaults") {
-      let template = Template(templateString: "Hello {{ name|default:a,b,c,\"World\" }}")
+      let template = Template(templateString: """
+        Hello {{ name|default:a,b,c,"World" }}
+        """)
       let result = try template.render(Context(dictionary: [:]))
       try expect(result) == "Hello World"
     }
+
+    it("can use int as default") {
+      let template = Template(templateString: "{{ value|default:1 }}")
+      let result = try template.render(Context(dictionary: [:]))
+      try expect(result) == "1"
+    }
+
+    it("can use float as default") {
+      let template = Template(templateString: "{{ value|default:1.5 }}")
+      let result = try template.render(Context(dictionary: [:]))
+      try expect(result) == "1.5"
+    }
+
+    it("checks for underlying nil value correctly") {
+      let template = Template(templateString: """
+        Hello {{ user.name|default:"anonymous" }}
+        """)
+      let nilName: String? = nil
+      let user: [String: Any?] = ["name": nilName]
+      let result = try template.render(Context(dictionary: ["user": user]))
+      try expect(result) == "Hello anonymous"
+    }
   }
 
-  describe("join filter") {
+  func testJoinFilter() {
-    let template = Template(templateString: "{{ value|join:\", \" }}")
+    let template = Template(templateString: """
+      {{ value|join:", " }}
+      """)
 
-    $0.it("joins a collection of strings") {
+    it("joins a collection of strings") {
       let result = try template.render(Context(dictionary: ["value": ["One", "Two"]]))
       try expect(result) == "One, Two"
     }
 
-    $0.it("joins a mixed-type collection") {
+    it("joins a mixed-type collection") {
       let result = try template.render(Context(dictionary: ["value": ["One", 2, true, 10.5, "Five"]]))
       try expect(result) == "One, 2, true, 10.5, Five"
     }
 
-    $0.it("can join by non string") {
+    it("can join by non string") {
-      let template = Template(templateString: "{{ value|join:separator }}")
+      let template = Template(templateString: """
+        {{ value|join:separator }}
+        """)
       let result = try template.render(Context(dictionary: ["value": ["One", "Two"], "separator": true]))
       try expect(result) == "OnetrueTwo"
     }
 
-    $0.it("can join without arguments") {
+    it("can join without arguments") {
-      let template = Template(templateString: "{{ value|join }}")
+      let template = Template(templateString: """
+        {{ value|join }}
+        """)
       let result = try template.render(Context(dictionary: ["value": ["One", "Two"]]))
       try expect(result) == "OneTwo"
     }
   }
+
+  func testSplitFilter() {
+    let template = Template(templateString: """
+      {{ value|split:", " }}
+      """)
+
+    it("split a string into array") {
+      let result = try template.render(Context(dictionary: ["value": "One, Two"]))
+      try expect(result) == """
+        ["One", "Two"]
+        """
+    }
+
+    it("can split without arguments") {
+      let template = Template(templateString: """
+        {{ value|split }}
+        """)
+      let result = try template.render(Context(dictionary: ["value": "One, Two"]))
+      try expect(result) == """
+        ["One,", "Two"]
+        """
+    }
+  }
+
+  func testFilterSuggestion() {
+    it("made for unknown filter") {
+      let template = Template(templateString: "{{ value|unknownFilter }}")
+      let filterExtension = Extension()
+      filterExtension.registerFilter("knownFilter") { value, _ in value }
+
+      try self.expectError(
+        reason: "Unknown filter 'unknownFilter'. Found similar filters: 'knownFilter'.",
+        token: "value|unknownFilter",
+        template: template,
+        extension: filterExtension
+      )
+    }
+
+    it("made for multiple similar filters") {
+      let template = Template(templateString: "{{ value|lowerFirst }}")
+      let filterExtension = Extension()
+      filterExtension.registerFilter("lowerFirstWord") { value, _ in value }
+      filterExtension.registerFilter("lowerFirstLetter") { value, _ in value }
+
+      try self.expectError(
+        reason: "Unknown filter 'lowerFirst'. Found similar filters: 'lowerFirstWord', 'lowercase'.",
+        token: "value|lowerFirst",
+        template: template,
+        extension: filterExtension
+      )
+    }
+
+    it("not made when can't find similar filter") {
+      let template = Template(templateString: "{{ value|unknownFilter }}")
+      let filterExtension = Extension()
+      filterExtension.registerFilter("lowerFirstWord") { value, _ in value }
+
+      try self.expectError(
+        reason: "Unknown filter 'unknownFilter'. Found similar filters: 'lowerFirstWord'.",
+        token: "value|unknownFilter",
+        template: template,
+        extension: filterExtension
+      )
+    }
+  }
+
+  func testIndentContent() throws {
+    let template = Template(templateString: """
+      {{ value|indent:2 }}
+      """)
+    let result = try template.render(Context(dictionary: [
+      "value": """
+      One
+      Two
+      """
+    ]))
+    try expect(result) == """
+      One
+        Two
+      """
+  }
+
+  func testIndentWithArbitraryCharacter() throws {
+    let template = Template(templateString: """
+      {{ value|indent:2,"\t" }}
+      """)
+    let result = try template.render(Context(dictionary: [
+      "value": """
+      One
+      Two
+      """
+    ]))
+    try expect(result) == """
+      One
+      \t\tTwo
+      """
+  }
+
+  func testIndentFirstLine() throws {
+    let template = Template(templateString: """
+      {{ value|indent:2," ",true }}
+      """)
+    let result = try template.render(Context(dictionary: [
+      "value": """
+      One
+      Two
+      """
+    ]))
+    // swiftlint:disable indentation_width
+    try expect(result) == """
+        One
+        Two
+      """
+    // swiftlint:enable indentation_width
+  }
+
+  func testIndentNotEmptyLines() throws {
+    let template = Template(templateString: """
+      {{ value|indent }}
+      """)
+    let result = try template.render(Context(dictionary: [
+      "value": """
+      One
+
+
+      Two
+
+
+      """
+    ]))
+    // swiftlint:disable indentation_width
+    try expect(result) == """
+      One
+
+
+          Two
+
+
+      """
+    // swiftlint:enable indentation_width
+  }
+
+  func testDynamicFilters() throws {
+    it("can apply dynamic filter") {
+      let template = Template(templateString: "{{ name|filter:somefilter }}")
+      let result = try template.render(Context(dictionary: ["name": "Jhon", "somefilter": "uppercase"]))
+      try expect(result) == "JHON"
+    }
+
+    it("can apply dynamic filter on array") {
+      let template = Template(templateString: "{{ values|filter:joinfilter }}")
+      let result = try template.render(Context(dictionary: ["values": [1, 2, 3], "joinfilter": "join:\", \""]))
+      try expect(result) == "1, 2, 3"
+    }
+
+    it("throws on unknown dynamic filter") {
+      let template = Template(templateString: "{{ values|filter:unknown }}")
+      let context = Context(dictionary: ["values": [1, 2, 3], "unknown": "absurd"])
+      try expect(try template.render(context)).toThrow()
+    }
+  }
+
+  private func expectError(
+    reason: String,
+    token: String,
+    template: Template,
+    extension: Extension,
+    file: String = #file,
+    line: Int = #line,
+    function: String = #function
+  ) throws {
+    guard let range = template.templateString.range(of: token) else {
+      fatalError("Can't find '\(token)' in '\(template)'")
+    }
+
+    let environment = Environment(extensions: [`extension`])
+    let expectedError: Error = {
+      let lexer = Lexer(templateString: template.templateString)
+      let location = lexer.rangeLocation(range)
+      let sourceMap = SourceMap(filename: template.name, location: location)
+      let token = Token.block(value: token, at: sourceMap)
+      return TemplateSyntaxError(reason: reason, token: token, stackTrace: [])
+    }()
+
+    let error = try expect(
+      environment.render(template: template, context: [:]),
+      file: file,
+      line: line,
+      function: function
+    ).toThrow() as TemplateSyntaxError
+    let reporter = SimpleErrorReporter()
+
+    try expect(
+      reporter.renderError(error),
+      file: file,
+      line: line,
+      function: function
+    ) == reporter.renderError(expectedError)
+  }
 }

Tests/StencilTests/FilterTagSpec.swift

@@ -1,25 +1,60 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 import Stencil
+import XCTest
 
-
+final class FilterTagTests: XCTestCase {
-func testFilterTag() {
+  func testFilterTag() {
-  describe("Filter Tag") {
+    it("allows you to use a filter") {
-    $0.it("allows you to use a filter") {
       let template = Template(templateString: "{% filter uppercase %}Test{% endfilter %}")
       let result = try template.render()
       try expect(result) == "TEST"
     }
 
-    $0.it("allows you to chain filters") {
+    it("allows you to chain filters") {
       let template = Template(templateString: "{% filter lowercase|capitalize %}TEST{% endfilter %}")
       let result = try template.render()
       try expect(result) == "Test"
     }
 
-    $0.it("errors without a filter") {
+    it("errors without a filter") {
-      let template = Template(templateString: "{% filter %}Test{% endfilter %}")
+      let template = Template(templateString: "Some {% filter %}Test{% endfilter %}")
       try expect(try template.render()).toThrow()
     }
 
+    it("can render filters with arguments") {
+      let ext = Extension()
+      ext.registerFilter("split") { value, args in
+        guard let value = value as? String,
+          let argument = args.first as? String else { return value }
+        return value.components(separatedBy: argument)
+      }
+      let env = Environment(extensions: [ext])
+      let result = try env.renderTemplate(string: """
+        {% filter split:","|join:";"  %}{{ items|join:"," }}{% endfilter %}
+        """, context: ["items": [1, 2]])
+      try expect(result) == "1;2"
+    }
+
+    it("can render filters with quote as an argument") {
+      let ext = Extension()
+      ext.registerFilter("replace") { value, args in
+        guard let value = value as? String,
+          args.count == 2,
+          let search = args.first as? String,
+          let replacement = args.last as? String else { return value }
+        return value.replacingOccurrences(of: search, with: replacement)
+      }
+      let env = Environment(extensions: [ext])
+      let result = try env.renderTemplate(string: """
+        {% filter replace:'"',"" %}{{ items|join:"," }}{% endfilter %}
+        """, context: ["items": ["\"1\"", "\"2\""]])
+      try expect(result) == "1,2"
+    }
   }
 }

Tests/StencilTests/ForNodeSpec.swift

@@ -1,43 +1,293 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 @testable import Stencil
-import Foundation
+import XCTest
 
+final class ForNodeTests: XCTestCase {
+  private let context = Context(dictionary: [
+    "items": [1, 2, 3],
+    "anyItems": [1, 2, 3] as [Any],
+    // swiftlint:disable:next legacy_objc_type
+    "nsItems": NSArray(array: [1, 2, 3]),
+    "emptyItems": [Int](),
+    "dict": [
+      "one": "I",
+      "two": "II"
+    ],
+    "tuples": [(1, 2, 3), (4, 5, 6)]
+  ])
 
-func testForNode() {
+  func testForNode() {
-  describe("ForNode") {
+    it("renders the given nodes for each item") {
-    let context = Context(dictionary: [
-      "items": [1, 2, 3],
-      "emptyItems": [Int](),
-      "dict": [
-        "one": "I",
-        "two": "II",
-      ]
-    ])
-
-    $0.it("renders the given nodes for each item") {
       let nodes: [NodeType] = [VariableNode(variable: "item")]
       let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
-      try expect(try node.render(context)) == "123"
+      try expect(try node.render(self.context)) == "123"
     }
 
-    $0.it("renders the given empty nodes when no items found item") {
+    it("renders the given empty nodes when no items found item") {
+      let node = ForNode(
+        resolvable: Variable("emptyItems"),
+        loopVariables: ["item"],
+        nodes: [VariableNode(variable: "item")],
+        emptyNodes: [TextNode(text: "empty")]
+      )
+      try expect(try node.render(self.context)) == "empty"
+    }
+
+    it("renders a context variable of type Array<Any>") {
+      let nodes: [NodeType] = [VariableNode(variable: "item")]
+      let node = ForNode(resolvable: Variable("anyItems"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      try expect(try node.render(self.context)) == "123"
+    }
+
+    #if os(OSX)
+    it("renders a context variable of type NSArray") {
+      let nodes: [NodeType] = [VariableNode(variable: "item")]
+      let node = ForNode(resolvable: Variable("nsItems"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      try expect(try node.render(self.context)) == "123"
+    }
+    #endif
+
+    it("can render a filter with spaces") {
+      let template = Template(templateString: """
+        {% for article in ars | default: a, b , articles %}\
+        - {{ article.title }} by {{ article.author }}.
+        {% endfor %}
+        """)
+      let context = Context(dictionary: [
+        "articles": [
+          Article(title: "Migrating from OCUnit to XCTest", author: "Kyle Fuller"),
+          Article(title: "Memory Management with ARC", author: "Kyle Fuller")
+        ]
+      ])
+      let result = try template.render(context)
+
+      try expect(result) == """
+        - Migrating from OCUnit to XCTest by Kyle Fuller.
+        - Memory Management with ARC by Kyle Fuller.
+
+        """
+    }
+  }
+
+  func testLoopMetadata() {
+    it("renders the given nodes while providing if the item is first in the context") {
+      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.first")]
+      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      try expect(try node.render(self.context)) == "1true2false3false"
+    }
+
+    it("renders the given nodes while providing if the item is last in the context") {
+      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.last")]
+      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      try expect(try node.render(self.context)) == "1false2false3true"
+    }
+
+    it("renders the given nodes while providing item counter") {
+      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.counter")]
+      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      try expect(try node.render(self.context)) == "112233"
+    }
+
+    it("renders the given nodes while providing item counter") {
+      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.counter0")]
+      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      try expect(try node.render(self.context)) == "102132"
+    }
+
+    it("renders the given nodes while providing loop length") {
+      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.length")]
+      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      try expect(try node.render(self.context)) == "132333"
+    }
+  }
+
+  func testWhereExpression() {
+    it("renders the given nodes while filtering items using where expression") {
+      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.counter")]
+      let parser = TokenParser(tokens: [], environment: Environment())
+      let `where` = try parser.compileExpression(components: ["item", ">", "1"], token: .text(value: "", at: .unknown))
+      let node = ForNode(
+        resolvable: Variable("items"),
+        loopVariables: ["item"],
+        nodes: nodes,
+        emptyNodes: [],
+        where: `where`
+      )
+      try expect(try node.render(self.context)) == "2132"
+    }
+
+    it("renders the given empty nodes when all items filtered out with where expression") {
       let nodes: [NodeType] = [VariableNode(variable: "item")]
       let emptyNodes: [NodeType] = [TextNode(text: "empty")]
-      let node = ForNode(resolvable: Variable("emptyItems"), loopVariables: ["item"], nodes: nodes, emptyNodes: emptyNodes)
+      let parser = TokenParser(tokens: [], environment: Environment())
-      try expect(try node.render(context)) == "empty"
+      let `where` = try parser.compileExpression(components: ["item", "==", "0"], token: .text(value: "", at: .unknown))
+      let node = ForNode(
+        resolvable: Variable("emptyItems"),
+        loopVariables: ["item"],
+        nodes: nodes,
+        emptyNodes: emptyNodes,
+        where: `where`
+      )
+      try expect(try node.render(self.context)) == "empty"
+    }
+  }
+
+  func testArrayOfTuples() {
+    it("can iterate over all tuple values") {
+      let template = Template(templateString: """
+        {% for first,second,third in tuples %}\
+        {{ first }}, {{ second }}, {{ third }}
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        1, 2, 3
+        4, 5, 6
+
+        """
     }
 
-    $0.it("renders a context variable of type Array<Any>") {
+    it("can iterate with less number of variables") {
-      let any_context = Context(dictionary: [
+      let template = Template(templateString: """
-        "items": ([1, 2, 3] as [Any])
+        {% for first,second in tuples %}\
+        {{ first }}, {{ second }}
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        1, 2
+        4, 5
+
+        """
+    }
+
+    it("can use _ to skip variables") {
+      let template = Template(templateString: """
+        {% for first,_,third in tuples %}\
+        {{ first }}, {{ third }}
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        1, 3
+        4, 6
+
+        """
+    }
+
+    it("throws when number of variables is more than number of tuple values") {
+      let template = Template(templateString: """
+        {% for key,value,smth in dict %}{% endfor %}
+        """)
+      try expect(template.render(self.context)).toThrow()
+    }
+  }
+
+  func testIterateDictionary() {
+    it("can iterate over dictionary") {
+      let template = Template(templateString: """
+        {% for key, value in dict %}\
+        {{ key }}: {{ value }},\
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        one: I,two: II,
+        """
+    }
+
+    it("renders supports iterating over dictionary") {
+      let nodes: [NodeType] = [
+        VariableNode(variable: "key"),
+        TextNode(text: ",")
+      ]
+      let emptyNodes: [NodeType] = [TextNode(text: "empty")]
+      let node = ForNode(
+        resolvable: Variable("dict"),
+        loopVariables: ["key"],
+        nodes: nodes,
+        emptyNodes: emptyNodes
+      )
+
+      try expect(node.render(self.context)) == """
+        one,two,
+        """
+    }
+
+    it("renders supports iterating over dictionary with values") {
+      let nodes: [NodeType] = [
+        VariableNode(variable: "key"),
+        TextNode(text: "="),
+        VariableNode(variable: "value"),
+        TextNode(text: ",")
+      ]
+      let emptyNodes: [NodeType] = [TextNode(text: "empty")]
+      let node = ForNode(
+        resolvable: Variable("dict"),
+        loopVariables: ["key", "value"],
+        nodes: nodes,
+        emptyNodes: emptyNodes
+      )
+
+      try expect(node.render(self.context)) == """
+        one=I,two=II,
+        """
+    }
+  }
+
+  func testIterateUsingMirroring() {
+    let nodes: [NodeType] = [
+      VariableNode(variable: "label"),
+      TextNode(text: "="),
+      VariableNode(variable: "value"),
+      TextNode(text: "\n")
+    ]
+    let node = ForNode(
+      resolvable: Variable("item"),
+      loopVariables: ["label", "value"],
+      nodes: nodes,
+      emptyNodes: []
+    )
+
+    it("can iterate over struct properties") {
+      let context = Context(dictionary: [
+        "item": MyStruct(string: "abc", number: 123)
       ])
+      try expect(node.render(context)) == """
+        string=abc
+        number=123
 
-      let nodes: [NodeType] = [VariableNode(variable: "item")]
+        """
-      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
-      try expect(try node.render(any_context)) == "123"
     }
 
-    $0.it("renders a context variable of type CountableClosedRange<Int>") {
+    it("can iterate tuple items") {
+      let context = Context(dictionary: [
+        "item": (one: 1, two: "dva")
+      ])
+      try expect(node.render(context)) == """
+        one=1
+        two=dva
+
+        """
+    }
+
+    it("can iterate over class properties") {
+      let context = Context(dictionary: [
+        "item": MySubclass("child", "base", 1)
+      ])
+      try expect(node.render(context)) == """
+        childString=child
+        baseString=base
+        baseInt=1
+
+        """
+    }
+  }
+
+  func testIterateRange() {
+    it("renders a context variable of type CountableClosedRange<Int>") {
       let context = Context(dictionary: ["range": 1...3])
       let nodes: [NodeType] = [VariableNode(variable: "item")]
       let node = ForNode(resolvable: Variable("range"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
@@ -45,7 +295,7 @@ func testForNode() {
       try expect(try node.render(context)) == "123"
     }
 
-    $0.it("renders a context variable of type CountableRange<Int>") {
+    it("renders a context variable of type CountableRange<Int>") {
       let context = Context(dictionary: ["range": 1..<4])
       let nodes: [NodeType] = [VariableNode(variable: "item")]
       let node = ForNode(resolvable: Variable("range"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
@@ -53,119 +303,295 @@ func testForNode() {
       try expect(try node.render(context)) == "123"
     }
 
-#if os(OSX)
+    it("can iterate in range of variables") {
-    $0.it("renders a context variable of type NSArray") {
+      let template: Template = "{% for i in 1...j %}{{ i }}{% endfor %}"
-      let nsarray_context = Context(dictionary: [
+      try expect(try template.render(Context(dictionary: ["j": 3]))) == "123"
-        "items": NSArray(array: [1, 2, 3])
-      ])
-
-      let nodes: [NodeType] = [VariableNode(variable: "item")]
-      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
-      try expect(try node.render(nsarray_context)) == "123"
     }
-#endif
+  }
 
-    $0.it("renders the given nodes while providing if the item is first in the context") {
+  func testHandleInvalidInput() throws {
-      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.first")]
+    let token = Token.block(value: "for i", at: .unknown)
-      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+    let parser = TokenParser(tokens: [token], environment: Environment())
-      try expect(try node.render(context)) == "1true2false3false"
+    let error = TemplateSyntaxError(
+      reason: "'for' statements should use the syntax: `for <x> in <y> [where <condition>]`.",
+      token: token
+    )
+    try expect(try parser.parse()).toThrow(error)
+  }
+
+  func testBreak() {
+    it("can break from loop") {
+      let template = Template(templateString: """
+        {% for item in items %}\
+        {{ item }}{% break %}\
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        1
+        """
     }
 
-    $0.it("renders the given nodes while providing if the item is last in the context") {
+    it("can break from inner node") {
-      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.last")]
+      let template = Template(templateString: """
-      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+        {% for item in items %}\
-      try expect(try node.render(context)) == "1false2false3true"
+        {{ item }}\
+        {% if forloop.first %}<{% break %}>{% endif %}!\
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        1<
+        """
     }
 
-    $0.it("renders the given nodes while providing item counter") {
+    it("does not allow break outside loop") {
-      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.counter")]
+      let template = Template(templateString: "{% for item in items %}{% endfor %}{% break %}")
-      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      let error = self.expectedSyntaxError(
-      try expect(try node.render(context)) == "112233"
+        token: "break",
+        template: template,
+        description: "'break' can be used only inside loop body"
+      )
+      try expect(template.render(self.context)).toThrow(error)
+    }
+  }
+
+  func testBreakNested() {
+    it("breaks outer loop") {
+      let template = Template(templateString: """
+        {% for item in items %}\
+        outer: {{ item }}
+        {% for item in items %}\
+        inner: {{ item }}
+        {% endfor %}\
+        {% break %}\
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        outer: 1
+        inner: 1
+        inner: 2
+        inner: 3
+
+        """
     }
 
-    $0.it("renders the given nodes while providing item counter") {
+    it("breaks inner loop") {
-      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.counter0")]
+      let template = Template(templateString: """
-      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+        {% for item in items %}\
-      try expect(try node.render(context)) == "102132"
+        outer: {{ item }}
+        {% for item in items %}\
+        inner: {{ item }}
+        {% break %}\
+        {% endfor %}\
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        outer: 1
+        inner: 1
+        outer: 2
+        inner: 1
+        outer: 3
+        inner: 1
+
+        """
+    }
+  }
+
+  func testBreakLabeled() {
+    it("breaks labeled loop") {
+      let template = Template(templateString: """
+        {% outer: for item in items %}\
+        outer: {{ item }}
+        {% for item in items %}\
+        {% break outer %}\
+        inner: {{ item }}
+        {% endfor %}\
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        outer: 1
+
+        """
     }
 
-    $0.it("renders the given nodes while filtering items using where expression") {
+    it("throws when breaking with unknown label") {
-        let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.counter")]
+      let template = Template(templateString: """
-        let `where` = try parseExpression(components: ["item", ">", "1"], tokenParser: TokenParser(tokens: [], environment: Environment()))
+        {% outer: for item in items %}
-        let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [], where: `where`)
+        {% break inner %}
-        try expect(try node.render(context)) == "2132"
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)).toThrow()
+    }
+  }
+
+  func testContinue() {
+    it("can continue loop") {
+      let template = Template(templateString: """
+        {% for item in items %}\
+        {{ item }}{% continue %}!\
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == "123"
     }
 
-    $0.it("renders the given empty nodes when all items filtered out with where expression") {
+    it("can continue from inner node") {
-        let nodes: [NodeType] = [VariableNode(variable: "item")]
+      let template = Template(templateString: """
-        let emptyNodes: [NodeType] = [TextNode(text: "empty")]
+        {% for item in items %}\
-        let `where` = try parseExpression(components: ["item", "==", "0"], tokenParser: TokenParser(tokens: [], environment: Environment()))
+        {% if forloop.last %}<{% continue %}>{% endif %}!\
-        let node = ForNode(resolvable: Variable("emptyItems"), loopVariables: ["item"], nodes: nodes, emptyNodes: emptyNodes, where: `where`)
+        {{ item }}\
-        try expect(try node.render(context)) == "empty"
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == "!1!2<"
     }
 
-    $0.it("can render a filter") {
+    it("does not allow continue outside loop") {
-      let templateString = "{% for article in ars|default:articles %}" +
+      let template = Template(templateString: "{% for item in items %}{% endfor %}{% continue %}")
-        "- {{ article.title }} by {{ article.author }}.\n" +
+      let error = self.expectedSyntaxError(
-        "{% endfor %}\n"
+        token: "continue",
+        template: template,
+        description: "'continue' can be used only inside loop body"
+      )
+      try expect(template.render(self.context)).toThrow(error)
+    }
+  }
 
-      let context = Context(dictionary: [
+  func testContinueNested() {
-        "articles": [
+    it("breaks outer loop") {
-          Article(title: "Migrating from OCUnit to XCTest", author: "Kyle Fuller"),
+      let template = Template(templateString: """
-          Article(title: "Memory Management with ARC", author: "Kyle Fuller"),
+        {% for item in items %}\
-        ]
+        {% for item in items %}\
-      ])
+        inner: {{ item }}\
+        {% endfor %}
+        {% continue %}
+        outer: {{ item }}
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        inner: 1inner: 2inner: 3
+        inner: 1inner: 2inner: 3
+        inner: 1inner: 2inner: 3
 
-      let template = Template(templateString: templateString)
+        """
-      let result = try template.render(context)
-
-      let fixture = "" +
-        "- Migrating from OCUnit to XCTest by Kyle Fuller.\n" +
-        "- Memory Management with ARC by Kyle Fuller.\n" +
-        "\n"
-
-      try expect(result) == fixture
     }
 
-    $0.it("can iterate over dictionary") {
+    it("breaks inner loop") {
-      let templateString = "{% for key,value in dict %}" +
+      let template = Template(templateString: """
-        "{{ key }}: {{ value }}\n" +
+        {% for item in items %}\
-        "{% endfor %}\n"
+        {% for item in items %}\
+        {% continue %}\
+        inner: {{ item }}
+        {% endfor %}\
+        outer: {{ item }}
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        outer: 1
+        outer: 2
+        outer: 3
 
-      let template = Template(templateString: templateString)
+        """
-      let result = try template.render(context)
+    }
+  }
 
-      let fixture = "one: I\ntwo: II\n\n"
+  func testContinueLabeled() {
-      try expect(result) == fixture
+    it("continues labeled loop") {
+      let template = Template(templateString: """
+        {% outer: for item in items %}\
+        {% for item in items %}\
+        inner: {{ item }}
+        {% continue outer %}\
+        {% endfor %}\
+        outer: {{ item }}
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        inner: 1
+        inner: 1
+        inner: 1
+
+        """
     }
 
-    $0.it("renders supports iterating over dictionary") {
+    it("throws when continuing with unknown label") {
-      let nodes: [NodeType] = [VariableNode(variable: "key")]
+      let template = Template(templateString: """
-      let emptyNodes: [NodeType] = [TextNode(text: "empty")]
+        {% outer: for item in items %}
-      let node = ForNode(resolvable: Variable("dict"), loopVariables: ["key"], nodes: nodes, emptyNodes: emptyNodes, where: nil)
+        {% continue inner %}
-      try expect(try node.render(context)) == "onetwo"
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)).toThrow()
+    }
+  }
+
+  func testAccessLabeled() {
+    it("can access labeled outer loop context from inner loop") {
+      let template = Template(templateString: """
+        {% outer: for item in 1...2 %}\
+        {% for item in items %}\
+        {{ forloop.counter }}-{{ forloop.outer.counter }},\
+        {% endfor %}---\
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        1-1,2-1,3-1,---1-2,2-2,3-2,---
+        """
     }
 
-    $0.it("renders supports iterating over dictionary") {
+    it("can access labeled outer loop from double inner loop") {
-      let nodes: [NodeType] = [VariableNode(variable: "key"), VariableNode(variable: "value")]
+      let template = Template(templateString: """
-      let emptyNodes: [NodeType] = [TextNode(text: "empty")]
+        {% outer: for item in 1...2 %}{% for item in 1...2 %}\
-      let node = ForNode(resolvable: Variable("dict"), loopVariables: ["key", "value"], nodes: nodes, emptyNodes: emptyNodes, where: nil)
+        {% for item in items %}\
-      try expect(try node.render(context)) == "oneItwoII"
+        {{ forloop.counter }}-{{ forloop.outer.counter }},\
+        {% endfor %}---{% endfor %}
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        1-1,2-1,3-1,---1-1,2-1,3-1,---
+        1-2,2-2,3-2,---1-2,2-2,3-2,---
+
+        """
     }
 
-    $0.it("handles invalid input") {
+    it("can access two labeled outer loop contexts from inner loop") {
-      let tokens: [Token] = [
+      let template = Template(templateString: """
-          .block(value: "for i"),
+        {% outer1: for item in 1...2 %}{% outer2: for item in 1...2 %}\
-      ]
+        {% for item in items %}\
-      let parser = TokenParser(tokens: tokens, environment: Environment())
+        {{ forloop.counter }}-{{ forloop.outer2.counter }}-{{ forloop.outer1.counter }},\
-      let error = TemplateSyntaxError("'for' statements should use the following 'for x in y where condition' `for i`.")
+        {% endfor %}---{% endfor %}
-      try expect(try parser.parse()).toThrow(error)
+        {% endfor %}
+        """)
+      try expect(template.render(self.context)) == """
+        1-1-1,2-1-1,3-1-1,---1-2-1,2-2-1,3-2-1,---
+        1-1-2,2-1-2,3-1-2,---1-2-2,2-2-2,3-2-2,---
+
+        """
     }
   }
 }
 
+// MARK: - Helpers
 
-fileprivate struct Article {
+private struct MyStruct {
+  let string: String
+  let number: Int
+}
+
+private struct Article {
   let title: String
   let author: String
 }
+
+private class MyClass {
+  var baseString: String
+  var baseInt: Int
+  init(_ string: String, _ int: Int) {
+    baseString = string
+    baseInt = int
+  }
+}
+
+private class MySubclass: MyClass {
+  var childString: String
+  init(_ childString: String, _ string: String, _ int: Int) {
+    self.childString = childString
+    super.init(string, int)
+  }
+}

Tests/StencilTests/Helpers.swift

@@ -0,0 +1,69 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import PathKit
+import Spectre
+@testable import Stencil
+import XCTest
+
+extension Expectation {
+  @discardableResult
+  func toThrow<T: Error>() throws -> T {
+    var thrownError: Error?
+
+    do {
+      _ = try expression()
+    } catch {
+      thrownError = error
+    }
+
+    if let thrownError = thrownError {
+      if let thrownError = thrownError as? T {
+        return thrownError
+      } else {
+        throw failure("\(thrownError) is not \(T.self)")
+      }
+    } else {
+      throw failure("expression did not throw an error")
+    }
+  }
+}
+
+extension XCTestCase {
+  func expectedSyntaxError(token: String, template: Template, description: String) -> TemplateSyntaxError {
+    guard let range = template.templateString.range(of: token) else {
+      fatalError("Can't find '\(token)' in '\(template)'")
+    }
+    let lexer = Lexer(templateString: template.templateString)
+    let location = lexer.rangeLocation(range)
+    let sourceMap = SourceMap(filename: template.name, location: location)
+    let token = Token.block(value: token, at: sourceMap)
+    return TemplateSyntaxError(reason: description, token: token, stackTrace: [])
+  }
+}
+
+// MARK: - Test Types
+
+class ExampleLoader: Loader {
+  func loadTemplate(name: String, environment: Environment) throws -> Template {
+    if name == "example.html" {
+      return Template(templateString: "Hello World!", environment: environment, name: name)
+    }
+
+    throw TemplateDoesNotExist(templateNames: [name], loader: self)
+  }
+}
+
+class ErrorNode: NodeType {
+  let token: Token?
+  init(token: Token? = nil) {
+    self.token = token
+  }
+
+  func render(_ context: Context) throws -> String {
+    throw TemplateSyntaxError("Custom Error")
+  }
+}

Tests/StencilTests/IfNodeSpec.swift

@@ -1,274 +1,296 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 @testable import Stencil
+import XCTest
 
-
+final class IfNodeTests: XCTestCase {
-func testIfNode() {
+  func testParseIf() {
-  describe("IfNode") {
+    it("can parse an if block") {
-    $0.describe("parsing") {
-      $0.it("can parse an if block") {
-        let tokens: [Token] = [
-          .block(value: "if value"),
-          .text(value: "true"),
-          .block(value: "endif")
-        ]
-
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let nodes = try parser.parse()
-        let node = nodes.first as? IfNode
-
-        let conditions = node?.conditions
-        try expect(conditions?.count) == 1
-        try expect(conditions?[0].nodes.count) == 1
-        let trueNode = conditions?[0].nodes.first as? TextNode
-        try expect(trueNode?.text) == "true"
-      }
-
-      $0.it("can parse an if with else block") {
-        let tokens: [Token] = [
-          .block(value: "if value"),
-          .text(value: "true"),
-          .block(value: "else"),
-          .text(value: "false"),
-          .block(value: "endif")
-        ]
-
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let nodes = try parser.parse()
-        let node = nodes.first as? IfNode
-
-        let conditions = node?.conditions
-        try expect(conditions?.count) == 2
-
-        try expect(conditions?[0].nodes.count) == 1
-        let trueNode = conditions?[0].nodes.first as? TextNode
-        try expect(trueNode?.text) == "true"
-
-        try expect(conditions?[1].nodes.count) == 1
-        let falseNode = conditions?[1].nodes.first as? TextNode
-        try expect(falseNode?.text) == "false"
-      }
-
-      $0.it("can parse an if with elif block") {
-        let tokens: [Token] = [
-          .block(value: "if value"),
-          .text(value: "true"),
-          .block(value: "elif something"),
-          .text(value: "some"),
-          .block(value: "else"),
-          .text(value: "false"),
-          .block(value: "endif")
-        ]
-
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let nodes = try parser.parse()
-        let node = nodes.first as? IfNode
-
-        let conditions = node?.conditions
-        try expect(conditions?.count) == 3
-
-        try expect(conditions?[0].nodes.count) == 1
-        let trueNode = conditions?[0].nodes.first as? TextNode
-        try expect(trueNode?.text) == "true"
-
-        try expect(conditions?[1].nodes.count) == 1
-        let elifNode = conditions?[1].nodes.first as? TextNode
-        try expect(elifNode?.text) == "some"
-
-        try expect(conditions?[2].nodes.count) == 1
-        let falseNode = conditions?[2].nodes.first as? TextNode
-        try expect(falseNode?.text) == "false"
-      }
-
-      $0.it("can parse an if with elif block without else") {
-        let tokens: [Token] = [
-          .block(value: "if value"),
-          .text(value: "true"),
-          .block(value: "elif something"),
-          .text(value: "some"),
-          .block(value: "endif")
-        ]
-
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let nodes = try parser.parse()
-        let node = nodes.first as? IfNode
-
-        let conditions = node?.conditions
-        try expect(conditions?.count) == 2
-
-        try expect(conditions?[0].nodes.count) == 1
-        let trueNode = conditions?[0].nodes.first as? TextNode
-        try expect(trueNode?.text) == "true"
-
-        try expect(conditions?[1].nodes.count) == 1
-        let elifNode = conditions?[1].nodes.first as? TextNode
-        try expect(elifNode?.text) == "some"
-      }
-
-      $0.it("can parse an if with multiple elif block") {
-        let tokens: [Token] = [
-          .block(value: "if value"),
-          .text(value: "true"),
-          .block(value: "elif something1"),
-          .text(value: "some1"),
-          .block(value: "elif something2"),
-          .text(value: "some2"),
-          .block(value: "else"),
-          .text(value: "false"),
-          .block(value: "endif")
-        ]
-
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let nodes = try parser.parse()
-        let node = nodes.first as? IfNode
-
-        let conditions = node?.conditions
-        try expect(conditions?.count) == 4
-
-        try expect(conditions?[0].nodes.count) == 1
-        let trueNode = conditions?[0].nodes.first as? TextNode
-        try expect(trueNode?.text) == "true"
-
-        try expect(conditions?[1].nodes.count) == 1
-        let elifNode = conditions?[1].nodes.first as? TextNode
-        try expect(elifNode?.text) == "some1"
-
-        try expect(conditions?[2].nodes.count) == 1
-        let elif2Node = conditions?[2].nodes.first as? TextNode
-        try expect(elif2Node?.text) == "some2"
-
-        try expect(conditions?[3].nodes.count) == 1
-        let falseNode = conditions?[3].nodes.first as? TextNode
-        try expect(falseNode?.text) == "false"
-      }
-
-
-      $0.it("can parse an if with complex expression") {
-        let tokens: [Token] = [
-          .block(value: "if value == \"test\" and not name"),
-          .text(value: "true"),
-          .block(value: "endif")
-        ]
-
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let nodes = try parser.parse()
-        try expect(nodes.first is IfNode).beTrue()
-      }
-
-      $0.it("can parse an ifnot block") {
-        let tokens: [Token] = [
-          .block(value: "ifnot value"),
-          .text(value: "false"),
-          .block(value: "else"),
-          .text(value: "true"),
-          .block(value: "endif")
-        ]
-
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let nodes = try parser.parse()
-        let node = nodes.first as? IfNode
-        let conditions = node?.conditions
-        try expect(conditions?.count) == 2
-
-        try expect(conditions?[0].nodes.count) == 1
-        let trueNode = conditions?[0].nodes.first as? TextNode
-        try expect(trueNode?.text) == "true"
-
-        try expect(conditions?[1].nodes.count) == 1
-        let falseNode = conditions?[1].nodes.first as? TextNode
-        try expect(falseNode?.text) == "false"
-      }
-
-      $0.it("throws an error when parsing an if block without an endif") {
-        let tokens: [Token] = [
-          .block(value: "if value"),
-        ]
-
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let error = TemplateSyntaxError("`endif` was not found.")
-        try expect(try parser.parse()).toThrow(error)
-      }
-
-      $0.it("throws an error when parsing an ifnot without an endif") {
-        let tokens: [Token] = [
-            .block(value: "ifnot value"),
-        ]
-
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let error = TemplateSyntaxError("`endif` was not found.")
-        try expect(try parser.parse()).toThrow(error)
-      }
-    }
-
-    $0.describe("rendering") {
-      $0.it("renders a true expression") {
-        let node = IfNode(conditions: [
-          IfCondition(expression: StaticExpression(value: true), nodes: [TextNode(text: "1")]),
-          IfCondition(expression: StaticExpression(value: true), nodes: [TextNode(text: "2")]),
-          IfCondition(expression: nil, nodes: [TextNode(text: "3")]),
-        ])
-
-        try expect(try node.render(Context())) == "1"
-      }
-
-      $0.it("renders the first true expression") {
-        let node = IfNode(conditions: [
-          IfCondition(expression: StaticExpression(value: false), nodes: [TextNode(text: "1")]),
-          IfCondition(expression: StaticExpression(value: true), nodes: [TextNode(text: "2")]),
-          IfCondition(expression: nil, nodes: [TextNode(text: "3")]),
-        ])
-
-        try expect(try node.render(Context())) == "2"
-      }
-
-      $0.it("renders the empty expression when other conditions are falsy") {
-        let node = IfNode(conditions: [
-          IfCondition(expression: StaticExpression(value: false), nodes: [TextNode(text: "1")]),
-          IfCondition(expression: StaticExpression(value: false), nodes: [TextNode(text: "2")]),
-          IfCondition(expression: nil, nodes: [TextNode(text: "3")]),
-        ])
-
-        try expect(try node.render(Context())) == "3"
-      }
-
-      $0.it("renders empty when no truthy conditions") {
-        let node = IfNode(conditions: [
-          IfCondition(expression: StaticExpression(value: false), nodes: [TextNode(text: "1")]),
-          IfCondition(expression: StaticExpression(value: false), nodes: [TextNode(text: "2")]),
-        ])
-
-        try expect(try node.render(Context())) == ""
-      }
-    }
-
-    $0.it("supports variable filters in the if expression") {
-        let tokens: [Token] = [
-          .block(value: "if value|uppercase == \"TEST\""),
-          .text(value: "true"),
-          .block(value: "endif")
-        ]
-
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let nodes = try parser.parse()
-
-        let result = try renderNodes(nodes, Context(dictionary: ["value": "test"]))
-        try expect(result) == "true"
-    }
-    
-    $0.it("evaluates nil properties as false") {
       let tokens: [Token] = [
-        .block(value: "if instance.value"),
+        .block(value: "if value", at: .unknown),
-        .text(value: "true"),
+        .text(value: "true", at: .unknown),
-        .block(value: "endif")
+        .block(value: "endif", at: .unknown)
       ]
-      
+
       let parser = TokenParser(tokens: tokens, environment: Environment())
       let nodes = try parser.parse()
-      
+      let node = nodes.first as? IfNode
-      struct SomeType {
+
-        let value: String? = nil
+      let conditions = node?.conditions
-      }
+      try expect(conditions?.count) == 1
-      let result = try renderNodes(nodes, Context(dictionary: ["instance": SomeType()]))
+      try expect(conditions?[0].nodes.count) == 1
-      try expect(result) == ""
+      let trueNode = conditions?[0].nodes.first as? TextNode
+      try expect(trueNode?.text) == "true"
+    }
+
+    it("can parse an if with complex expression") {
+      let tokens: [Token] = [
+        .block(value: """
+          if value == \"test\" and (not name or not (name and surname) or( some )and other )
+          """, at: .unknown),
+        .text(value: "true", at: .unknown),
+        .block(value: "endif", at: .unknown)
+      ]
+
+      let parser = TokenParser(tokens: tokens, environment: Environment())
+      let nodes = try parser.parse()
+      try expect(nodes.first is IfNode).beTrue()
     }
   }
+
+  func testParseIfWithElse() throws {
+    let tokens: [Token] = [
+      .block(value: "if value", at: .unknown),
+      .text(value: "true", at: .unknown),
+      .block(value: "else", at: .unknown),
+      .text(value: "false", at: .unknown),
+      .block(value: "endif", at: .unknown)
+    ]
+
+    let parser = TokenParser(tokens: tokens, environment: Environment())
+    let nodes = try parser.parse()
+    let node = nodes.first as? IfNode
+
+    let conditions = node?.conditions
+    try expect(conditions?.count) == 2
+
+    try expect(conditions?[0].nodes.count) == 1
+    let trueNode = conditions?[0].nodes.first as? TextNode
+    try expect(trueNode?.text) == "true"
+
+    try expect(conditions?[1].nodes.count) == 1
+    let falseNode = conditions?[1].nodes.first as? TextNode
+    try expect(falseNode?.text) == "false"
+  }
+
+  func testParseIfWithElif() throws {
+    let tokens: [Token] = [
+      .block(value: "if value", at: .unknown),
+      .text(value: "true", at: .unknown),
+      .block(value: "elif something", at: .unknown),
+      .text(value: "some", at: .unknown),
+      .block(value: "else", at: .unknown),
+      .text(value: "false", at: .unknown),
+      .block(value: "endif", at: .unknown)
+    ]
+
+    let parser = TokenParser(tokens: tokens, environment: Environment())
+    let nodes = try parser.parse()
+    let node = nodes.first as? IfNode
+
+    let conditions = node?.conditions
+    try expect(conditions?.count) == 3
+
+    try expect(conditions?[0].nodes.count) == 1
+    let trueNode = conditions?[0].nodes.first as? TextNode
+    try expect(trueNode?.text) == "true"
+
+    try expect(conditions?[1].nodes.count) == 1
+    let elifNode = conditions?[1].nodes.first as? TextNode
+    try expect(elifNode?.text) == "some"
+
+    try expect(conditions?[2].nodes.count) == 1
+    let falseNode = conditions?[2].nodes.first as? TextNode
+    try expect(falseNode?.text) == "false"
+  }
+
+  func testParseIfWithElifWithoutElse() throws {
+    let tokens: [Token] = [
+      .block(value: "if value", at: .unknown),
+      .text(value: "true", at: .unknown),
+      .block(value: "elif something", at: .unknown),
+      .text(value: "some", at: .unknown),
+      .block(value: "endif", at: .unknown)
+    ]
+
+    let parser = TokenParser(tokens: tokens, environment: Environment())
+    let nodes = try parser.parse()
+    let node = nodes.first as? IfNode
+
+    let conditions = node?.conditions
+    try expect(conditions?.count) == 2
+
+    try expect(conditions?[0].nodes.count) == 1
+    let trueNode = conditions?[0].nodes.first as? TextNode
+    try expect(trueNode?.text) == "true"
+
+    try expect(conditions?[1].nodes.count) == 1
+    let elifNode = conditions?[1].nodes.first as? TextNode
+    try expect(elifNode?.text) == "some"
+  }
+
+  func testParseMultipleElif() throws {
+    let tokens: [Token] = [
+      .block(value: "if value", at: .unknown),
+      .text(value: "true", at: .unknown),
+      .block(value: "elif something1", at: .unknown),
+      .text(value: "some1", at: .unknown),
+      .block(value: "elif something2", at: .unknown),
+      .text(value: "some2", at: .unknown),
+      .block(value: "else", at: .unknown),
+      .text(value: "false", at: .unknown),
+      .block(value: "endif", at: .unknown)
+    ]
+
+    let parser = TokenParser(tokens: tokens, environment: Environment())
+    let nodes = try parser.parse()
+    let node = nodes.first as? IfNode
+
+    let conditions = node?.conditions
+    try expect(conditions?.count) == 4
+
+    try expect(conditions?[0].nodes.count) == 1
+    let trueNode = conditions?[0].nodes.first as? TextNode
+    try expect(trueNode?.text) == "true"
+
+    try expect(conditions?[1].nodes.count) == 1
+    let elifNode = conditions?[1].nodes.first as? TextNode
+    try expect(elifNode?.text) == "some1"
+
+    try expect(conditions?[2].nodes.count) == 1
+    let elif2Node = conditions?[2].nodes.first as? TextNode
+    try expect(elif2Node?.text) == "some2"
+
+    try expect(conditions?[3].nodes.count) == 1
+    let falseNode = conditions?[3].nodes.first as? TextNode
+    try expect(falseNode?.text) == "false"
+  }
+
+  func testParseIfnot() throws {
+    let tokens: [Token] = [
+      .block(value: "ifnot value", at: .unknown),
+      .text(value: "false", at: .unknown),
+      .block(value: "else", at: .unknown),
+      .text(value: "true", at: .unknown),
+      .block(value: "endif", at: .unknown)
+    ]
+
+    let parser = TokenParser(tokens: tokens, environment: Environment())
+    let nodes = try parser.parse()
+    let node = nodes.first as? IfNode
+    let conditions = node?.conditions
+    try expect(conditions?.count) == 2
+
+    try expect(conditions?[0].nodes.count) == 1
+    let trueNode = conditions?[0].nodes.first as? TextNode
+    try expect(trueNode?.text) == "true"
+
+    try expect(conditions?[1].nodes.count) == 1
+    let falseNode = conditions?[1].nodes.first as? TextNode
+    try expect(falseNode?.text) == "false"
+  }
+
+  func testParsingErrors() {
+    it("throws an error when parsing an if block without an endif") {
+      let tokens: [Token] = [.block(value: "if value", at: .unknown)]
+
+      let parser = TokenParser(tokens: tokens, environment: Environment())
+      let error = TemplateSyntaxError(reason: "`endif` was not found.", token: tokens.first)
+      try expect(try parser.parse()).toThrow(error)
+    }
+
+    it("throws an error when parsing an ifnot without an endif") {
+      let tokens: [Token] = [.block(value: "ifnot value", at: .unknown)]
+
+      let parser = TokenParser(tokens: tokens, environment: Environment())
+      let error = TemplateSyntaxError(reason: "`endif` was not found.", token: tokens.first)
+      try expect(try parser.parse()).toThrow(error)
+    }
+  }
+
+  func testRendering() {
+    it("renders a true expression") {
+      let node = IfNode(conditions: [
+        IfCondition(expression: VariableExpression(variable: Variable("true")), nodes: [TextNode(text: "1")]),
+        IfCondition(expression: VariableExpression(variable: Variable("true")), nodes: [TextNode(text: "2")]),
+        IfCondition(expression: nil, nodes: [TextNode(text: "3")])
+      ])
+
+      try expect(try node.render(Context())) == "1"
+    }
+
+    it("renders the first true expression") {
+      let node = IfNode(conditions: [
+        IfCondition(expression: VariableExpression(variable: Variable("false")), nodes: [TextNode(text: "1")]),
+        IfCondition(expression: VariableExpression(variable: Variable("true")), nodes: [TextNode(text: "2")]),
+        IfCondition(expression: nil, nodes: [TextNode(text: "3")])
+      ])
+
+      try expect(try node.render(Context())) == "2"
+    }
+
+    it("renders the empty expression when other conditions are falsy") {
+      let node = IfNode(conditions: [
+        IfCondition(expression: VariableExpression(variable: Variable("false")), nodes: [TextNode(text: "1")]),
+        IfCondition(expression: VariableExpression(variable: Variable("false")), nodes: [TextNode(text: "2")]),
+        IfCondition(expression: nil, nodes: [TextNode(text: "3")])
+      ])
+
+      try expect(try node.render(Context())) == "3"
+    }
+
+    it("renders empty when no truthy conditions") {
+      let node = IfNode(conditions: [
+        IfCondition(expression: VariableExpression(variable: Variable("false")), nodes: [TextNode(text: "1")]),
+        IfCondition(expression: VariableExpression(variable: Variable("false")), nodes: [TextNode(text: "2")])
+      ])
+
+      try expect(try node.render(Context())) == ""
+    }
+  }
+
+  func testSupportVariableFilters() throws {
+    let tokens: [Token] = [
+      .block(value: "if value|uppercase == \"TEST\"", at: .unknown),
+      .text(value: "true", at: .unknown),
+      .block(value: "endif", at: .unknown)
+    ]
+
+    let parser = TokenParser(tokens: tokens, environment: Environment())
+    let nodes = try parser.parse()
+
+    let result = try renderNodes(nodes, Context(dictionary: ["value": "test"]))
+    try expect(result) == "true"
+  }
+
+  func testEvaluatesNilAsFalse() throws {
+    let tokens: [Token] = [
+      .block(value: "if instance.value", at: .unknown),
+      .text(value: "true", at: .unknown),
+      .block(value: "endif", at: .unknown)
+    ]
+
+    let parser = TokenParser(tokens: tokens, environment: Environment())
+    let nodes = try parser.parse()
+
+    let result = try renderNodes(nodes, Context(dictionary: ["instance": SomeType()]))
+    try expect(result) == ""
+  }
+
+  func testSupportsRangeVariables() throws {
+    let tokens: [Token] = [
+      .block(value: "if value in 1...3", at: .unknown),
+      .text(value: "true", at: .unknown),
+      .block(value: "else", at: .unknown),
+      .text(value: "false", at: .unknown),
+      .block(value: "endif", at: .unknown)
+    ]
+
+    let parser = TokenParser(tokens: tokens, environment: Environment())
+    let nodes = try parser.parse()
+
+    try expect(renderNodes(nodes, Context(dictionary: ["value": 3]))) == "true"
+    try expect(renderNodes(nodes, Context(dictionary: ["value": 4]))) == "false"
+  }
+}
+
+// MARK: - Helpers
+
+private struct SomeType {
+  let value: String? = nil
 }

Tests/StencilTests/IncludeSpec.swift

@@ -1,61 +1,78 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import PathKit
 import Spectre
 @testable import Stencil
-import PathKit
+import XCTest
 
+final class IncludeTests: XCTestCase {
+  private let path = Path(#file as String) + ".." + "fixtures"
+  private lazy var loader = FileSystemLoader(paths: [path])
+  private lazy var environment = Environment(loader: loader)
 
-func testInclude() {
+  func testParsing() {
-  describe("Include") {
+    it("throws an error when no template is given") {
-    let path = Path(#file) + ".." + "fixtures"
+      let tokens: [Token] = [ .block(value: "include", at: .unknown) ]
-    let loader = FileSystemLoader(paths: [path])
+      let parser = TokenParser(tokens: tokens, environment: Environment())
-    let environment = Environment(loader: loader)
 
-    $0.describe("parsing") {
+      let error = TemplateSyntaxError(reason: """
-      $0.it("throws an error when no template is given") {
+        'include' tag requires one argument, the template file to be included. \
-        let tokens: [Token] = [ .block(value: "include") ]
+        A second optional argument can be used to specify the context that will \
-        let parser = TokenParser(tokens: tokens, environment: Environment())
+        be passed to the included file
+        """, token: tokens.first)
+      try expect(try parser.parse()).toThrow(error)
+    }
 
-        let error = TemplateSyntaxError("'include' tag takes one argument, the template file to be included")
+    it("can parse a valid include block") {
-        try expect(try parser.parse()).toThrow(error)
+      let tokens: [Token] = [ .block(value: "include \"test.html\"", at: .unknown) ]
-      }
+      let parser = TokenParser(tokens: tokens, environment: Environment())
 
-      $0.it("can parse a valid include block") {
+      let nodes = try parser.parse()
-        let tokens: [Token] = [ .block(value: "include \"test.html\"") ]
+      let node = nodes.first as? IncludeNode
-        let parser = TokenParser(tokens: tokens, environment: Environment())
+      try expect(nodes.count) == 1
+      try expect(node?.templateName) == Variable("\"test.html\"")
+    }
+  }
 
-        let nodes = try parser.parse()
+  func testRendering() {
-        let node = nodes.first as? IncludeNode
+    it("throws an error when rendering without a loader") {
-        try expect(nodes.count) == 1
+      let node = IncludeNode(templateName: Variable("\"test.html\""), token: .block(value: "", at: .unknown))
-        try expect(node?.templateName) == Variable("\"test.html\"")
+
+      do {
+        _ = try node.render(Context())
+      } catch {
+        try expect("\(error)") == "Template named `test.html` does not exist. No loaders found"
       }
     }
 
-    $0.describe("rendering") {
+    it("throws an error when it cannot find the included template") {
-      $0.it("throws an error when rendering without a loader") {
+      let node = IncludeNode(templateName: Variable("\"unknown.html\""), token: .block(value: "", at: .unknown))
-        let node = IncludeNode(templateName: Variable("\"test.html\""))
 
-        do {
+      do {
-          _ = try node.render(Context())
+        _ = try node.render(Context(environment: self.environment))
-        } catch {
+      } catch {
-          try expect("\(error)") == "Template named `test.html` does not exist. No loaders found"
+        try expect("\(error)".hasPrefix("Template named `unknown.html` does not exist in loader")).to.beTrue()
-        }
       }
+    }
 
-      $0.it("throws an error when it cannot find the included template") {
+    it("successfully renders a found included template") {
-        let node = IncludeNode(templateName: Variable("\"unknown.html\""))
+      let node = IncludeNode(templateName: Variable("\"test.html\""), token: .block(value: "", at: .unknown))
+      let context = Context(dictionary: ["target": "World"], environment: self.environment)
+      let value = try node.render(context)
+      try expect(value) == "Hello World!"
+    }
 
-        do {
+    it("successfully passes context") {
-          _ = try node.render(Context(environment: environment))
+      let template = Template(templateString: """
-        } catch {
+        {% include "test.html" child %}
-          try expect("\(error)".hasPrefix("Template named `unknown.html` does not exist in loader")).to.beTrue()
+        """)
-        }
+      let context = Context(dictionary: ["child": ["target": "World"]], environment: self.environment)
-      }
+      let value = try template.render(context)
-
+      try expect(value) == "Hello World!"
-      $0.it("successfully renders a found included template") {
-        let node = IncludeNode(templateName: Variable("\"test.html\""))
-        let context = Context(dictionary: ["target": "World"], environment: environment)
-        let value = try node.render(context)
-        try expect(value) == "Hello World!"
-      }
     }
   }
 }

Tests/StencilTests/InheritanceSpec.swift

@@ -0,0 +1,79 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import PathKit
+import Spectre
+import Stencil
+import XCTest
+
+final class InheritanceTests: XCTestCase {
+  private let path = Path(#file as String) + ".." + "fixtures"
+  private lazy var loader = FileSystemLoader(paths: [path])
+  private lazy var environment = Environment(loader: loader)
+
+  func testInheritance() {
+    it("can inherit from another template") {
+      let template = try self.environment.loadTemplate(name: "child.html")
+      try expect(try template.render()) == """
+        Super_Header Child_Header
+        Child_Body
+        """
+    }
+
+    it("can inherit from another template inheriting from another template") {
+      let template = try self.environment.loadTemplate(name: "child-child.html")
+      try expect(try template.render()) == """
+        Super_Header Child_Header Child_Child_Header
+        Child_Body
+        """
+    }
+
+    it("can inherit from a template that calls a super block") {
+      let template = try self.environment.loadTemplate(name: "child-super.html")
+      try expect(try template.render()) == """
+        Header
+        Child_Body
+        """
+    }
+
+    it("can render block.super in if tag") {
+      let template = try self.environment.loadTemplate(name: "if-block-child.html")
+
+      try expect(try template.render(["sort": "new"])) == """
+      Title - Nieuwste spellen
+
+      """
+
+      try expect(try template.render(["sort": "upcoming"])) == """
+      Title - Binnenkort op de agenda
+
+      """
+
+      try expect(try template.render(["sort": "near-me"])) == """
+      Title - In mijn buurt
+
+      """
+    }
+  }
+
+  func testInheritanceCache() {
+    it("can call block twice") {
+      let template: Template = "{% block repeat %}Block{% endblock %}{{ block.repeat }}"
+      try expect(try template.render()) == "BlockBlock"
+    }
+
+    it("renders child content when calling block twice in base template") {
+      let template = try self.environment.loadTemplate(name: "child-repeat.html")
+      try expect(try template.render()) == """
+      Super_Header Child_Header
+      Child_Body
+      Repeat
+      Super_Header Child_Header
+      Child_Body
+      """
+    }
+  }
+}

Tests/StencilTests/InheritenceSpec.swift

@@ -1,27 +0,0 @@
-import Spectre
-import Stencil
-import PathKit
-
-
-func testInheritence() {
-  describe("Inheritence") {
-    let path = Path(#file) + ".." + "fixtures"
-    let loader = FileSystemLoader(paths: [path])
-    let environment = Environment(loader: loader)
-
-    $0.it("can inherit from another template") {
-      let template = try environment.loadTemplate(name: "child.html")
-      try expect(try template.render()) == "Header\nChild"
-    }
-
-    $0.it("can inherit from another template inheriting from another template") {
-      let template = try environment.loadTemplate(name: "child-child.html")
-      try expect(try template.render()) == "Child Child Header\nChild"
-    }
-
-    $0.it("can inherit from a template that calls a super block") {
-      let template = try environment.loadTemplate(name: "child-super.html")
-      try expect(try template.render()) == "Header\nChild Body"
-    }
-  }
-}

Tests/StencilTests/LexerSpec.swift

@@ -1,68 +1,167 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import PathKit
 import Spectre
 @testable import Stencil
+import XCTest
 
+final class LexerTests: XCTestCase {
+  func testText() throws {
+    let lexer = Lexer(templateString: "Hello World")
+    let tokens = lexer.tokenize()
 
-func testLexer() {
+    try expect(tokens.count) == 1
-  describe("Lexer") {
+    try expect(tokens.first) == .text(value: "Hello World", at: makeSourceMap("Hello World", for: lexer))
-    $0.it("can tokenize text") {
+  }
-      let lexer = Lexer(templateString: "Hello World")
-      let tokens = lexer.tokenize()
 
-      try expect(tokens.count) == 1
+  func testComment() throws {
-      try expect(tokens.first) == .text(value: "Hello World")
+    let lexer = Lexer(templateString: "{# Comment #}")
-    }
+    let tokens = lexer.tokenize()
 
-    $0.it("can tokenize a comment") {
+    try expect(tokens.count) == 1
-      let lexer = Lexer(templateString: "{# Comment #}")
+    try expect(tokens.first) == .comment(value: "Comment", at: makeSourceMap("Comment", for: lexer))
-      let tokens = lexer.tokenize()
+  }
 
-      try expect(tokens.count) == 1
+  func testVariable() throws {
-      try expect(tokens.first) == .comment(value: "Comment")
+    let lexer = Lexer(templateString: "{{ Variable }}")
-    }
+    let tokens = lexer.tokenize()
 
-    $0.it("can tokenize a variable") {
+    try expect(tokens.count) == 1
-      let lexer = Lexer(templateString: "{{ Variable }}")
+    try expect(tokens.first) == .variable(value: "Variable", at: makeSourceMap("Variable", for: lexer))
-      let tokens = lexer.tokenize()
+  }
 
-      try expect(tokens.count) == 1
+  func testTokenWithoutSpaces() throws {
-      try expect(tokens.first) == .variable(value: "Variable")
+    let lexer = Lexer(templateString: "{{Variable}}")
-    }
+    let tokens = lexer.tokenize()
 
-    $0.it("can tokenize unclosed tag by ignoring it") {
+    try expect(tokens.count) == 1
-      let lexer = Lexer(templateString: "{{ thing")
+    try expect(tokens.first) == .variable(value: "Variable", at: makeSourceMap("Variable", for: lexer))
-      let tokens = lexer.tokenize()
+  }
 
-      try expect(tokens.count) == 1
+  func testUnclosedTag() throws {
-      try expect(tokens.first) == .text(value: "")
+    let templateString = "{{ thing"
-    }
+    let lexer = Lexer(templateString: templateString)
+    let tokens = lexer.tokenize()
 
-    $0.it("can tokenize a mixture of content") {
+    try expect(tokens.count) == 1
-      let lexer = Lexer(templateString: "My name is {{ name }}.")
+    try expect(tokens.first) == .text(value: "", at: makeSourceMap("{{ thing", for: lexer))
-      let tokens = lexer.tokenize()
+  }
 
-      try expect(tokens.count) == 3
+  func testContentMixture() throws {
-      try expect(tokens[0]) == Token.text(value: "My name is ")
+    let templateString = "My name is {{ myname }}."
-      try expect(tokens[1]) == Token.variable(value: "name")
+    let lexer = Lexer(templateString: templateString)
-      try expect(tokens[2]) == Token.text(value: ".")
+    let tokens = lexer.tokenize()
-    }
 
-    $0.it("can tokenize two variables without being greedy") {
+    try expect(tokens.count) == 3
-      let lexer = Lexer(templateString: "{{ thing }}{{ name }}")
+    try expect(tokens[0]) == .text(value: "My name is ", at: makeSourceMap("My name is ", for: lexer))
-      let tokens = lexer.tokenize()
+    try expect(tokens[1]) == .variable(value: "myname", at: makeSourceMap("myname", for: lexer))
+    try expect(tokens[2]) == .text(value: ".", at: makeSourceMap(".", for: lexer))
+  }
 
-      try expect(tokens.count) == 2
+  func testVariablesWithoutBeingGreedy() throws {
-      try expect(tokens[0]) == Token.variable(value: "thing")
+    let templateString = "{{ thing }}{{ name }}"
-      try expect(tokens[1]) == Token.variable(value: "name")
+    let lexer = Lexer(templateString: templateString)
-    }
+    let tokens = lexer.tokenize()
 
-    $0.it("can tokenize an unclosed block") {
+    try expect(tokens.count) == 2
-      let lexer = Lexer(templateString: "{%}")
+    try expect(tokens[0]) == .variable(value: "thing", at: makeSourceMap("thing", for: lexer))
-      let _ = lexer.tokenize()
+    try expect(tokens[1]) == .variable(value: "name", at: makeSourceMap("name", for: lexer))
-    }
+  }
 
-    $0.it("can tokenize an empty variable") {
+  func testUnclosedBlock() throws {
-      let lexer = Lexer(templateString: "{{}}")
+    let lexer = Lexer(templateString: "{%}")
-      let _ = lexer.tokenize()
+    _ = lexer.tokenize()
+  }
+
+  func testTokenizeIncorrectSyntaxWithoutCrashing() throws {
+    let lexer = Lexer(templateString: "func some() {{% if %}")
+    _ = lexer.tokenize()
+  }
+
+  func testEmptyVariable() throws {
+    let lexer = Lexer(templateString: "{{}}")
+    _ = lexer.tokenize()
+  }
+
+  func testNewlines() throws {
+    // swiftlint:disable indentation_width
+    let templateString = """
+      My name is {%
+          if name
+           and
+          name
+      %}{{
+      name
+      }}{%
+      endif %}.
+      """
+    // swiftlint:enable indentation_width
+    let lexer = Lexer(templateString: templateString)
+    let tokens = lexer.tokenize()
+
+    try expect(tokens.count) == 5
+    try expect(tokens[0]) == .text(value: "My name is ", at: makeSourceMap("My name is", for: lexer))
+    try expect(tokens[1]) == .block(value: "if name and name", at: makeSourceMap("{%", for: lexer))
+    try expect(tokens[2]) == .variable(value: "name", at: makeSourceMap("name", for: lexer, options: .backwards))
+    try expect(tokens[3]) == .block(value: "endif", at: makeSourceMap("endif", for: lexer))
+    try expect(tokens[4]) == .text(value: ".", at: makeSourceMap(".", for: lexer))
+  }
+
+  func testTrimSymbols() throws {
+    let fBlock = "if hello"
+    let sBlock = "ta da"
+    let lexer = Lexer(templateString: "{%+ \(fBlock) -%}{% \(sBlock) -%}")
+    let tokens = lexer.tokenize()
+    let behaviours = (
+      WhitespaceBehaviour(leading: .keep, trailing: .trim),
+      WhitespaceBehaviour(leading: .unspecified, trailing: .trim)
+    )
+
+    try expect(tokens.count) == 2
+    try expect(tokens[0]) == .block(value: fBlock, at: makeSourceMap(fBlock, for: lexer), whitespace: behaviours.0)
+    try expect(tokens[1]) == .block(value: sBlock, at: makeSourceMap(sBlock, for: lexer), whitespace: behaviours.1)
+  }
+
+  func testEscapeSequence() throws {
+    let templateString = "class Some {{ '{' }}{% if true %}{{ stuff }}{% endif %}"
+    let lexer = Lexer(templateString: templateString)
+    let tokens = lexer.tokenize()
+
+    try expect(tokens.count) == 5
+    try expect(tokens[0]) == .text(value: "class Some ", at: makeSourceMap("class Some ", for: lexer))
+    try expect(tokens[1]) == .variable(value: "'{'", at: makeSourceMap("'{'", for: lexer))
+    try expect(tokens[2]) == .block(value: "if true", at: makeSourceMap("if true", for: lexer))
+    try expect(tokens[3]) == .variable(value: "stuff", at: makeSourceMap("stuff", for: lexer))
+    try expect(tokens[4]) == .block(value: "endif", at: makeSourceMap("endif", for: lexer))
+  }
+
+  func testPerformance() throws {
+    let path = Path(#file as String) + ".." + "fixtures" + "huge.html"
+    let content: String = try path.read()
+
+    measure {
+      let lexer = Lexer(templateString: content)
+      _ = lexer.tokenize()
     }
   }
+
+  func testCombiningDiaeresis() throws {
+    // the symbol "ü" in the `templateString` is unusually encoded as 0x75 0xCC 0x88 (LATIN SMALL LETTER U + COMBINING
+    // DIAERESIS) instead of 0xC3 0xBC (LATIN SMALL LETTER U WITH DIAERESIS)
+    let templateString = "ü\n{% if test %}ü{% endif %}\n{% if ü %}ü{% endif %}\n"
+    let lexer = Lexer(templateString: templateString)
+    let tokens = lexer.tokenize()
+
+    try expect(tokens.count) == 9
+    assert(tokens[1].contents == "if test")
+  }
+
+  private func makeSourceMap(_ token: String, for lexer: Lexer, options: String.CompareOptions = []) -> SourceMap {
+    guard let range = lexer.templateString.range(of: token, options: options) else { fatalError("Token not found") }
+    return SourceMap(location: lexer.rangeLocation(range))
+  }
 }

Tests/StencilTests/LoaderSpec.swift

@@ -1,54 +1,60 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import PathKit
 import Spectre
 import Stencil
-import PathKit
+import XCTest
 
-
+final class TemplateLoaderTests: XCTestCase {
-func testTemplateLoader() {
+  func testFileSystemLoader() {
-  describe("FileSystemLoader") {
+    let path = Path(#file as String) + ".." + "fixtures"
-    let path = Path(#file) + ".."  + "fixtures"
     let loader = FileSystemLoader(paths: [path])
     let environment = Environment(loader: loader)
 
-    $0.it("errors when a template cannot be found") {
+    it("errors when a template cannot be found") {
       try expect(try environment.loadTemplate(name: "unknown.html")).toThrow()
     }
 
-    $0.it("errors when an array of templates cannot be found") {
+    it("errors when an array of templates cannot be found") {
       try expect(try environment.loadTemplate(names: ["unknown.html", "unknown2.html"])).toThrow()
     }
 
-    $0.it("can load a template from a file") {
+    it("can load a template from a file") {
       _ = try environment.loadTemplate(name: "test.html")
     }
 
-    $0.it("errors when loading absolute file outside of the selected path") {
+    it("errors when loading absolute file outside of the selected path") {
       try expect(try environment.loadTemplate(name: "/etc/hosts")).toThrow()
     }
 
-    $0.it("errors when loading relative file outside of the selected path") {
+    it("errors when loading relative file outside of the selected path") {
       try expect(try environment.loadTemplate(name: "../LoaderSpec.swift")).toThrow()
     }
   }
 
-  describe("DictionaryLoader") {
+  func testDictionaryLoader() {
     let loader = DictionaryLoader(templates: [
-        "index.html": "Hello World"
+      "index.html": "Hello World"
     ])
     let environment = Environment(loader: loader)
 
-    $0.it("errors when a template cannot be found") {
+    it("errors when a template cannot be found") {
       try expect(try environment.loadTemplate(name: "unknown.html")).toThrow()
     }
 
-    $0.it("errors when an array of templates cannot be found") {
+    it("errors when an array of templates cannot be found") {
       try expect(try environment.loadTemplate(names: ["unknown.html", "unknown2.html"])).toThrow()
     }
 
-    $0.it("can load a template from a known templates") {
+    it("can load a template from a known templates") {
       _ = try environment.loadTemplate(name: "index.html")
     }
 
-    $0.it("can load a known template from a collection of templates") {
+    it("can load a known template from a collection of templates") {
       _ = try environment.loadTemplate(names: ["unknown.html", "index.html"])
     }
   }

Tests/StencilTests/NodeSpec.swift

@@ -1,60 +1,117 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 @testable import Stencil
+import XCTest
 
+final class NodeTests: XCTestCase {
+  private let context = Context(dictionary: [
+    "name": "Kyle",
+    "age": 27,
+    "items": [1, 2, 3]
+  ])
 
-class ErrorNode : NodeType {
+  func testTextNode() {
-  func render(_ context: Context) throws -> String {
+    it("renders the given text") {
-    throw TemplateSyntaxError("Custom Error")
+      let node = TextNode(text: "Hello World")
+      try expect(try node.render(self.context)) == "Hello World"
+    }
+    it("Trims leading whitespace") {
+      let text = "      \n Some text     "
+      let trimBehaviour = TrimBehaviour(leading: .whitespace, trailing: .nothing)
+      let node = TextNode(text: text, trimBehaviour: trimBehaviour)
+      try expect(try node.render(self.context)) == "\n Some text     "
+    }
+    it("Trims leading whitespace and one newline") {
+      let text = "\n\n Some text     "
+      let trimBehaviour = TrimBehaviour(leading: .whitespaceAndOneNewLine, trailing: .nothing)
+      let node = TextNode(text: text, trimBehaviour: trimBehaviour)
+      try expect(try node.render(self.context)) == "\n Some text     "
+    }
+    it("Trims leading whitespace and one newline") {
+      let text = "\n\n Some text     "
+      let trimBehaviour = TrimBehaviour(leading: .whitespaceAndNewLines, trailing: .nothing)
+      let node = TextNode(text: text, trimBehaviour: trimBehaviour)
+      try expect(try node.render(self.context)) == "Some text     "
+    }
+    it("Trims trailing whitespace") {
+      let text = "      Some text     \n"
+      let trimBehaviour = TrimBehaviour(leading: .nothing, trailing: .whitespace)
+      let node = TextNode(text: text, trimBehaviour: trimBehaviour)
+      try expect(try node.render(self.context)) == "      Some text\n"
+    }
+    it("Trims trailing whitespace and one newline") {
+      let text = "      Some text     \n \n "
+      let trimBehaviour = TrimBehaviour(leading: .nothing, trailing: .whitespaceAndOneNewLine)
+      let node = TextNode(text: text, trimBehaviour: trimBehaviour)
+      try expect(try node.render(self.context)) == "      Some text     \n "
+    }
+    it("Trims trailing whitespace and newlines") {
+      let text = "      Some text     \n \n "
+      let trimBehaviour = TrimBehaviour(leading: .nothing, trailing: .whitespaceAndNewLines)
+      let node = TextNode(text: text, trimBehaviour: trimBehaviour)
+      try expect(try node.render(self.context)) == "      Some text"
+    }
+    it("Trims all whitespace") {
+      let text = "    \n  \nSome text \n    "
+      let trimBehaviour = TrimBehaviour(leading: .whitespaceAndNewLines, trailing: .whitespaceAndNewLines)
+      let node = TextNode(text: text, trimBehaviour: trimBehaviour)
+      try expect(try node.render(self.context)) == "Some text"
+    }
   }
-}
 
-
+  func testVariableNode() {
-func testNode() {
+    it("resolves and renders the variable") {
-  describe("Node") {
+      let node = VariableNode(variable: Variable("name"))
-    let context = Context(dictionary: [
+      try expect(try node.render(self.context)) == "Kyle"
-      "name": "Kyle",
-      "age": 27,
-      "items": [1, 2, 3],
-    ])
-
-    $0.describe("TextNode") {
-      $0.it("renders the given text") {
-        let node = TextNode(text: "Hello World")
-        try expect(try node.render(context)) == "Hello World"
-      }
     }
 
-    $0.describe("VariableNode") {
+    it("resolves and renders a non string variable") {
-      $0.it("resolves and renders the variable") {
+      let node = VariableNode(variable: Variable("age"))
-        let node = VariableNode(variable: Variable("name"))
+      try expect(try node.render(self.context)) == "27"
-        try expect(try node.render(context)) == "Kyle"
+    }
-      }
+  }
 
-      $0.it("resolves and renders a non string variable") {
+  func testRendering() {
-        let node = VariableNode(variable: Variable("age"))
+    it("renders the nodes") {
-        try expect(try node.render(context)) == "27"
+      let nodes: [NodeType] = [
-      }
+        TextNode(text: "Hello "),
+        VariableNode(variable: "name")
+      ]
+
+      try expect(try renderNodes(nodes, self.context)) == "Hello Kyle"
     }
 
-    $0.describe("rendering nodes") {
+    it("correctly throws a nodes failure") {
-      $0.it("renders the nodes") {
+      let nodes: [NodeType] = [
-        let nodes: [NodeType] = [
+        TextNode(text: "Hello "),
-          TextNode(text:"Hello "),
+        VariableNode(variable: "name"),
-          VariableNode(variable: "name"),
+        ErrorNode()
-        ]
+      ]
 
-        try expect(try renderNodes(nodes, context)) == "Hello Kyle"
+      try expect(try renderNodes(nodes, self.context)).toThrow(TemplateSyntaxError("Custom Error"))
-      }
+    }
+  }
 
-      $0.it("correctly throws a nodes failure") {
+  func testRenderingBooleans() {
-        let nodes: [NodeType] = [
+    it("can render true & false") {
-          TextNode(text:"Hello "),
+      try expect(Template(templateString: "{{ true }}").render()) == "true"
-          VariableNode(variable: "name"),
+      try expect(Template(templateString: "{{ false }}").render()) == "false"
-          ErrorNode(),
+    }
-        ]
 
-        try expect(try renderNodes(nodes, context)).toThrow(TemplateSyntaxError("Custom Error"))
+    it("can resolve variable") {
-      }
+      let template = Template(templateString: "{{ value == \"known\" }}")
+      try expect(template.render(["value": "known"])) == "true"
+      try expect(template.render(["value": "unknown"])) == "false"
+    }
+
+    it("can render a boolean expression") {
+      try expect(Template(templateString: "{{ 1 > 0 }}").render()) == "true"
+      try expect(Template(templateString: "{{ 1 == 2 }}").render()) == "false"
     }
   }
 }

Tests/StencilTests/NowNodeSpec.swift

@@ -1,43 +1,56 @@
-import Foundation
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 @testable import Stencil
+import XCTest
 
+final class NowNodeTests: XCTestCase {
+  func testParsing() {
+    it("parses default format without any now arguments") {
+      #if os(Linux)
+      throw skip()
+      #else
+      let tokens: [Token] = [ .block(value: "now", at: .unknown) ]
+      let parser = TokenParser(tokens: tokens, environment: Environment())
 
-func testNowNode() {
+      let nodes = try parser.parse()
-#if !os(Linux)
+      let node = nodes.first as? NowNode
-  describe("NowNode") {
+      try expect(nodes.count) == 1
-    $0.describe("parsing") {
+      try expect(node?.format.variable) == "\"yyyy-MM-dd 'at' HH:mm\""
-      $0.it("parses default format without any now arguments") {
+      #endif
-        let tokens: [Token] = [ .block(value: "now") ]
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-
-        let nodes = try parser.parse()
-        let node = nodes.first as? NowNode
-        try expect(nodes.count) == 1
-        try expect(node?.format.variable) == "\"yyyy-MM-dd 'at' HH:mm\""
-      }
-
-      $0.it("parses now with a format") {
-        let tokens: [Token] = [ .block(value: "now \"HH:mm\"") ]
-        let parser = TokenParser(tokens: tokens, environment: Environment())
-        let nodes = try parser.parse()
-        let node = nodes.first as? NowNode
-        try expect(nodes.count) == 1
-        try expect(node?.format.variable) == "\"HH:mm\""
-      }
     }
 
-    $0.describe("rendering") {
+    it("parses now with a format") {
-      $0.it("renders the date") {
+      #if os(Linux)
-        let node = NowNode(format: Variable("\"yyyy-MM-dd\""))
+      throw skip()
-
+      #else
-        let formatter = DateFormatter()
+      let tokens: [Token] = [ .block(value: "now \"HH:mm\"", at: .unknown) ]
-        formatter.dateFormat = "yyyy-MM-dd"
+      let parser = TokenParser(tokens: tokens, environment: Environment())
-        let date = formatter.string(from: NSDate() as Date)
+      let nodes = try parser.parse()
-
+      let node = nodes.first as? NowNode
-        try expect(try node.render(Context())) == date
+      try expect(nodes.count) == 1
-      }
+      try expect(node?.format.variable) == "\"HH:mm\""
+      #endif
+    }
+  }
+
+  func testRendering() {
+    it("renders the date") {
+      #if os(Linux)
+      throw skip()
+      #else
+      let node = NowNode(format: Variable("\"yyyy-MM-dd\""))
+
+      let formatter = DateFormatter()
+      formatter.dateFormat = "yyyy-MM-dd"
+      let date = formatter.string(from: Date())
+
+      try expect(try node.render(Context())) == date
+      #endif
     }
   }
-#endif
 }

Tests/StencilTests/ParserSpec.swift

@@ -1,62 +1,85 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 @testable import Stencil
+import XCTest
 
+final class TokenParserTests: XCTestCase {
+  func testTextToken() throws {
+    let parser = TokenParser(tokens: [
+      .text(value: "Hello World", at: .unknown)
+    ], environment: Environment())
 
-func testTokenParser() {
+    let nodes = try parser.parse()
-  describe("TokenParser") {
+    let node = nodes.first as? TextNode
-    $0.it("can parse a text token") {
-      let parser = TokenParser(tokens: [
-        .text(value: "Hello World")
-      ], environment: Environment())
 
-      let nodes = try parser.parse()
+    try expect(nodes.count) == 1
-      let node = nodes.first as? TextNode
+    try expect(node?.text) == "Hello World"
+  }
 
-      try expect(nodes.count) == 1
+  func testVariableToken() throws {
-      try expect(node?.text) == "Hello World"
+    let parser = TokenParser(tokens: [
+      .variable(value: "'name'", at: .unknown)
+    ], environment: Environment())
+
+    let nodes = try parser.parse()
+    let node = nodes.first as? VariableNode
+    try expect(nodes.count) == 1
+    let result = try node?.render(Context())
+    try expect(result) == "name"
+  }
+
+  func testCommentToken() throws {
+    let parser = TokenParser(tokens: [
+      .comment(value: "Secret stuff!", at: .unknown)
+    ], environment: Environment())
+
+    let nodes = try parser.parse()
+    try expect(nodes.count) == 0
+  }
+
+  func testTagToken() throws {
+    let simpleExtension = Extension()
+    simpleExtension.registerSimpleTag("known") { _ in
+      ""
     }
 
-    $0.it("can parse a variable token") {
+    let parser = TokenParser(tokens: [
-      let parser = TokenParser(tokens: [
+      .block(value: "known", at: .unknown)
-        .variable(value: "'name'")
+    ], environment: Environment(extensions: [simpleExtension]))
-      ], environment: Environment())
 
-      let nodes = try parser.parse()
+    let nodes = try parser.parse()
-      let node = nodes.first as? VariableNode
+    try expect(nodes.count) == 1
-      try expect(nodes.count) == 1
+  }
-      let result = try node?.render(Context())
-      try expect(result) == "name"
-    }
 
-    $0.it("can parse a comment token") {
+  func testErrorUnknownTag() throws {
-      let parser = TokenParser(tokens: [
+    let tokens: [Token] = [.block(value: "unknown", at: .unknown)]
-        .comment(value: "Secret stuff!")
+    let parser = TokenParser(tokens: tokens, environment: Environment())
-      ], environment: Environment())
 
-      let nodes = try parser.parse()
+    try expect(try parser.parse()).toThrow(TemplateSyntaxError(
-      try expect(nodes.count) == 0
+      reason: "Unknown template tag 'unknown'",
-    }
+      token: tokens.first
+    ))
+  }
 
-    $0.it("can parse a tag token") {
+  func testTransformWhitespaceBehaviourToTrimBehaviour() throws {
-      let simpleExtension = Extension()
+    let simpleExtension = Extension()
-      simpleExtension.registerSimpleTag("known") { _ in
+    simpleExtension.registerSimpleTag("known") { _ in "" }
-        return ""
-      }
 
-      let parser = TokenParser(tokens: [
+    let parser = TokenParser(tokens: [
-        .block(value: "known"),
+      .block(value: "known", at: .unknown, whitespace: WhitespaceBehaviour(leading: .unspecified, trailing: .trim)),
-      ], environment: Environment(extensions: [simpleExtension]))
+      .text(value: "      \nSome text     ", at: .unknown),
+      .block(value: "known", at: .unknown, whitespace: WhitespaceBehaviour(leading: .keep, trailing: .trim))
+    ], environment: Environment(extensions: [simpleExtension]))
 
-      let nodes = try parser.parse()
+    let nodes = try parser.parse()
-      try expect(nodes.count) == 1
+    try expect(nodes.count) == 3
-    }
+    let textNode = nodes[1] as? TextNode
-
+    try expect(textNode?.text) == "      \nSome text     "
-    $0.it("errors when parsing an unknown tag") {
+    try expect(textNode?.trimBehaviour) == TrimBehaviour(leading: .whitespaceAndNewLines, trailing: .nothing)
-      let parser = TokenParser(tokens: [
-        .block(value: "unknown"),
-      ], environment: Environment())
-
-      try expect(try parser.parse()).toThrow(TemplateSyntaxError("Unknown template tag 'unknown'"))
-    }
   }
 }

Tests/StencilTests/StencilSpec.swift

@@ -1,69 +1,76 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 import Stencil
+import XCTest
 
-
+final class StencilTests: XCTestCase {
-fileprivate class CustomNode : NodeType {
+  private lazy var environment: Environment = {
-  func render(_ context:Context) throws -> String {
-    return "Hello World"
-  }
-}
-
-
-fileprivate struct Article {
-  let title: String
-  let author: String
-}
-
-
-func testStencil() {
-  describe("Stencil") {
     let exampleExtension = Extension()
-
+    exampleExtension.registerSimpleTag("simpletag") { _ in
-    exampleExtension.registerSimpleTag("simpletag") { context in
+      "Hello World"
-      return "Hello World"
     }
-
+    exampleExtension.registerTag("customtag") { _, token in
-    exampleExtension.registerTag("customtag") { parser, token in
+      CustomNode(token: token)
-      return CustomNode()
     }
+    return Environment(extensions: [exampleExtension])
+  }()
 
-    let environment = Environment(extensions: [exampleExtension])
+  func testStencil() {
+    it("can render the README example") {
+      let templateString = """
+        There are {{ articles.count }} articles.
 
-    $0.it("can render the README example") {
+        {% for article in articles %}\
-
+          - {{ article.title }} by {{ article.author }}.
-      let templateString = "There are {{ articles.count }} articles.\n" +
+        {% endfor %}
-        "\n" +
+        """
-        "{% for article in articles %}" +
-        "    - {{ article.title }} by {{ article.author }}.\n" +
-        "{% endfor %}\n"
 
       let context = [
         "articles": [
           Article(title: "Migrating from OCUnit to XCTest", author: "Kyle Fuller"),
-          Article(title: "Memory Management with ARC", author: "Kyle Fuller"),
+          Article(title: "Memory Management with ARC", author: "Kyle Fuller")
         ]
       ]
 
       let template = Template(templateString: templateString)
       let result = try template.render(context)
 
-      let fixture = "There are 2 articles.\n" +
+      try expect(result) == """
-        "\n" +
+        There are 2 articles.
-        "    - Migrating from OCUnit to XCTest by Kyle Fuller.\n" +
-        "    - Memory Management with ARC by Kyle Fuller.\n" +
-        "\n"
 
-      try expect(result) == fixture
+          - Migrating from OCUnit to XCTest by Kyle Fuller.
+          - Memory Management with ARC by Kyle Fuller.
+
+        """
     }
 
-    $0.it("can render a custom template tag") {
+    it("can render a custom template tag") {
-      let result = try environment.renderTemplate(string: "{% customtag %}")
+      let result = try self.environment.renderTemplate(string: "{% customtag %}")
       try expect(result) == "Hello World"
     }
 
-    $0.it("can render a simple custom tag") {
+    it("can render a simple custom tag") {
-      let result = try environment.renderTemplate(string: "{% simpletag %}")
+      let result = try self.environment.renderTemplate(string: "{% simpletag %}")
       try expect(result) == "Hello World"
     }
   }
 }
+
+// MARK: - Helpers
+
+private struct CustomNode: NodeType {
+  let token: Token?
+  func render(_ context: Context) throws -> String {
+    "Hello World"
+  }
+}
+
+private struct Article {
+  let title: String
+  let author: String
+}

Tests/StencilTests/TemplateSpec.swift

@@ -1,19 +1,25 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
-import Stencil
+@testable import Stencil
+import XCTest
 
-
+final class TemplateTests: XCTestCase {
-func testTemplate() {
+  func testTemplate() {
-  describe("Template") {
+    it("can render a template from a string") {
-    $0.it("can render a template from a string") {
       let template = Template(templateString: "Hello World")
       let result = try template.render([ "name": "Kyle" ])
       try expect(result) == "Hello World"
     }
 
-    $0.it("can render a template from a string literal") {
+    it("can render a template from a string literal") {
-        let template: Template = "Hello World"
+      let template: Template = "Hello World"
-        let result = try template.render([ "name": "Kyle" ])
+      let result = try template.render([ "name": "Kyle" ])
-        try expect(result) == "Hello World"
+      try expect(result) == "Hello World"
     }
   }
 }

Tests/StencilTests/TokenSpec.swift

@@ -1,30 +1,36 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
-import Stencil
+@testable import Stencil
+import XCTest
 
-
+final class TokenTests: XCTestCase {
-func testToken() {
+  func testToken() {
-  describe("Token") {
+    it("can split the contents into components") {
-    $0.it("can split the contents into components") {
+      let token = Token.text(value: "hello world", at: .unknown)
-      let token = Token.text(value: "hello world")
+      let components = token.components
-      let components = token.components()
 
       try expect(components.count) == 2
       try expect(components[0]) == "hello"
       try expect(components[1]) == "world"
     }
 
-    $0.it("can split the contents into components with single quoted strings") {
+    it("can split the contents into components with single quoted strings") {
-      let token = Token.text(value: "hello 'kyle fuller'")
+      let token = Token.text(value: "hello 'kyle fuller'", at: .unknown)
-      let components = token.components()
+      let components = token.components
 
       try expect(components.count) == 2
       try expect(components[0]) == "hello"
       try expect(components[1]) == "'kyle fuller'"
     }
 
-    $0.it("can split the contents into components with double quoted strings") {
+    it("can split the contents into components with double quoted strings") {
-      let token = Token.text(value: "hello \"kyle fuller\"")
+      let token = Token.text(value: "hello \"kyle fuller\"", at: .unknown)
-      let components = token.components()
+      let components = token.components
 
       try expect(components.count) == 2
       try expect(components[0]) == "hello"

Tests/StencilTests/TrimBehaviourSpec.swift

@@ -0,0 +1,143 @@
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
+import Spectre
+import Stencil
+import XCTest
+
+final class TrimBehaviourTests: XCTestCase {
+  func testSmartTrimCanRemoveNewlines() throws {
+    let templateString = """
+      {% for item in items %}
+        - {{item}}
+      {% endfor %}
+      text
+      """
+
+    let context = ["items": ["item 1", "item 2"]]
+    let template = Template(templateString: templateString, environment: .init(trimBehaviour: .smart))
+    let result = try template.render(context)
+
+    // swiftlint:disable indentation_width
+    try expect(result) == """
+        - item 1
+        - item 2
+      text
+      """
+    // swiftlint:enable indentation_width
+  }
+
+  func testSmartTrimOnlyRemoveSingleNewlines() throws {
+    let templateString = """
+      {% for item in items %}
+
+        - {{item}}
+      {% endfor %}
+      text
+      """
+
+    let context = ["items": ["item 1", "item 2"]]
+    let template = Template(templateString: templateString, environment: .init(trimBehaviour: .smart))
+    let result = try template.render(context)
+
+    // swiftlint:disable indentation_width
+    try expect(result) == """
+
+        - item 1
+
+        - item 2
+      text
+      """
+    // swiftlint:enable indentation_width
+  }
+
+  func testSmartTrimCanRemoveNewlinesWhileKeepingWhitespace() throws {
+    // swiftlint:disable indentation_width
+    let templateString = """
+          Items:
+          {% for item in items %}
+              - {{item}}
+          {% endfor %}
+      """
+    // swiftlint:enable indentation_width
+
+    let context = ["items": ["item 1", "item 2"]]
+    let template = Template(templateString: templateString, environment: .init(trimBehaviour: .smart))
+    let result = try template.render(context)
+
+    // swiftlint:disable indentation_width
+    try expect(result) == """
+          Items:
+              - item 1
+              - item 2
+
+      """
+    // swiftlint:enable indentation_width
+  }
+
+  func testTrimSymbols() {
+    it("Respects whitespace control symbols in for tags") {
+      // swiftlint:disable indentation_width
+      let template: Template = """
+        {% for num in numbers -%}
+            {{num}}
+        {%- endfor %}
+        """
+      // swiftlint:enable indentation_width
+      let result = try template.render([ "numbers": Array(1...9) ])
+      try expect(result) == "123456789"
+    }
+    it("Respects whitespace control symbols in if tags") {
+      let template: Template = """
+        {% if value -%}
+          {{text}}
+        {%- endif %}
+        """
+      let result = try template.render([ "text": "hello", "value": true ])
+      try expect(result) == "hello"
+    }
+  }
+
+  func testTrimSymbolsOverridingEnvironment() {
+    let environment = Environment(trimBehaviour: .all)
+
+    it("respects whitespace control symbols in if tags") {
+      // swiftlint:disable indentation_width
+      let templateString = """
+          {% if value +%}
+          {{text}}
+        {%+ endif %}
+
+        """
+      // swiftlint:enable indentation_width
+      let template = Template(templateString: templateString, environment: environment)
+      let result = try template.render([ "text": "hello", "value": true ])
+      try expect(result) == "\n  hello\n"
+    }
+
+    it("can customize blocks on same line as text") {
+      // swiftlint:disable indentation_width
+      let templateString = """
+            Items:{% for item in items +%}
+                - {{item}}
+            {%- endfor %}
+        """
+      // swiftlint:enable indentation_width
+
+      let context = ["items": ["item 1", "item 2"]]
+      let template = Template(templateString: templateString, environment: environment)
+      let result = try template.render(context)
+
+      // swiftlint:disable indentation_width
+      try expect(result) == """
+            Items:
+                - item 1
+                - item 2
+        """
+      // swiftlint:enable indentation_width
+    }
+  }
+}

Tests/StencilTests/VariableSpec.swift

@@ -1,127 +1,404 @@
-import Foundation
+//
+// Stencil
+// Copyright © 2022 Stencil
+// MIT Licence
+//
+
 import Spectre
 @testable import Stencil
+import XCTest
 
+final class VariableTests: XCTestCase {
+  private let context: Context = {
+    let ext = Extension()
+    ext.registerFilter("incr") { arg in
+      (arg.flatMap { toNumber(value: $0) } ?? 0) + 1
+    }
+    let environment = Environment(extensions: [ext])
 
-#if os(OSX)
+    var context = Context(dictionary: [
-@objc class Object : NSObject {
-  let title = "Hello World"
-}
-#endif
-
-fileprivate struct Person {
-  let name: String
-}
-
-fileprivate struct Article {
-  let author: Person
-}
-
-
-func testVariable() {
-  describe("Variable") {
-    let context = Context(dictionary: [
       "name": "Kyle",
       "contacts": ["Katie", "Carlton"],
       "profiles": [
-        "github": "kylef",
+        "github": "kylef"
       ],
       "counter": [
-        "count": "kylef",
+        "count": "kylef"
-        ],
+      ],
-      "article": Article(author: Person(name: "Kyle"))
+      "article": Article(author: Person(name: "Kyle")),
-    ])
+      "blog": Blog(),
-
+      "tuple": (one: 1, two: 2),
-#if os(OSX)
+      "dynamic": [
+        "enum": DynamicEnum.someValue,
+        "struct": DynamicStruct()
+      ]
+    ], environment: environment)
+    #if os(OSX)
     context["object"] = Object()
-#endif
+    #endif
+    return context
+  }()
 
-    $0.it("can resolve a string literal with double quotes") {
+  func testLiterals() {
+    it("can resolve a string literal with double quotes") {
       let variable = Variable("\"name\"")
-      let result = try variable.resolve(context) as? String
+      let result = try variable.resolve(self.context) as? String
       try expect(result) == "name"
     }
 
-    $0.it("can resolve a string literal with single quotes") {
+    it("can resolve a string literal with one double quote") {
+      let variable = Variable("\"")
+      let result = try variable.resolve(self.context) as? String
+      try expect(result).to.beNil()
+    }
+
+    it("can resolve a string literal with single quotes") {
       let variable = Variable("'name'")
-      let result = try variable.resolve(context) as? String
+      let result = try variable.resolve(self.context) as? String
       try expect(result) == "name"
     }
 
-    $0.it("can resolve an integer literal") {
+    it("can resolve a string literal with one single quote") {
+      let variable = Variable("'")
+      let result = try variable.resolve(self.context) as? String
+      try expect(result).to.beNil()
+    }
+
+    it("can resolve an integer literal") {
       let variable = Variable("5")
-      let result = try variable.resolve(context) as? Number
+      let result = try variable.resolve(self.context) as? Int
       try expect(result) == 5
     }
 
-    $0.it("can resolve an float literal") {
+    it("can resolve an float literal") {
       let variable = Variable("3.14")
-      let result = try variable.resolve(context) as? Number
+      let result = try variable.resolve(self.context) as? Number
       try expect(result) == 3.14
     }
 
-    $0.it("can resolve a string variable") {
+    it("can resolve boolean literal") {
+      try expect(Variable("true").resolve(self.context) as? Bool) == true
+      try expect(Variable("false").resolve(self.context) as? Bool) == false
+      try expect(Variable("0").resolve(self.context) as? Int) == 0
+      try expect(Variable("1").resolve(self.context) as? Int) == 1
+    }
+  }
+
+  func testVariable() {
+    it("can resolve a string variable") {
       let variable = Variable("name")
-      let result = try variable.resolve(context) as? String
+      let result = try variable.resolve(self.context) as? String
       try expect(result) == "Kyle"
     }
+  }
 
-    $0.it("can resolve an item from a dictionary") {
+  func testDictionary() {
+    it("can resolve an item from a dictionary") {
       let variable = Variable("profiles.github")
-      let result = try variable.resolve(context) as? String
+      let result = try variable.resolve(self.context) as? String
       try expect(result) == "kylef"
     }
 
-    $0.it("can resolve an item from an array via it's index") {
+    it("can get the count of a dictionary") {
+      let variable = Variable("profiles.count")
+      let result = try variable.resolve(self.context) as? Int
+      try expect(result) == 1
+    }
+  }
+
+  func testArray() {
+    it("can resolve an item from an array via it's index") {
       let variable = Variable("contacts.0")
-      let result = try variable.resolve(context) as? String
+      let result = try variable.resolve(self.context) as? String
       try expect(result) == "Katie"
 
-        let variable1 = Variable("contacts.1")
+      let variable1 = Variable("contacts.1")
-        let result1 = try variable1.resolve(context) as? String
+      let result1 = try variable1.resolve(self.context) as? String
-        try expect(result1) == "Carlton"
+      try expect(result1) == "Carlton"
     }
 
-    $0.it("can resolve an item from an array via unknown index") {
+    it("can resolve an item from an array via unknown index") {
       let variable = Variable("contacts.5")
-      let result = try variable.resolve(context) as? String
+      let result = try variable.resolve(self.context) as? String
       try expect(result).to.beNil()
 
       let variable1 = Variable("contacts.-5")
-      let result1 = try variable1.resolve(context) as? String
+      let result1 = try variable1.resolve(self.context) as? String
       try expect(result1).to.beNil()
     }
 
-    $0.it("can resolve the first item from an array") {
+    it("can resolve the first item from an array") {
       let variable = Variable("contacts.first")
-      let result = try variable.resolve(context) as? String
+      let result = try variable.resolve(self.context) as? String
       try expect(result) == "Katie"
     }
 
-    $0.it("can resolve the last item from an array") {
+    it("can resolve the last item from an array") {
       let variable = Variable("contacts.last")
-      let result = try variable.resolve(context) as? String
+      let result = try variable.resolve(self.context) as? String
       try expect(result) == "Carlton"
     }
+  }
 
-    $0.it("can resolve a property with reflection") {
+  func testDynamicMemberLookup() {
+    it("can resolve dynamic member lookup") {
+      let variable = Variable("dynamic.struct.test")
+      let result = try variable.resolve(self.context) as? String
+      try expect(result) == "this is a dynamic response"
+    }
+
+    it("can resolve dynamic enum rawValue") {
+      let variable = Variable("dynamic.enum.rawValue")
+      let result = try variable.resolve(self.context) as? String
+      try expect(result) == "this is raw value"
+    }
+  }
+
+  func testReflection() {
+    it("can resolve a property with reflection") {
       let variable = Variable("article.author.name")
-      let result = try variable.resolve(context) as? String
+      let result = try variable.resolve(self.context) as? String
       try expect(result) == "Kyle"
     }
 
-    $0.it("can get the count of a dictionary") {
+    it("can resolve a value via reflection") {
-      let variable = Variable("profiles.count")
+      let variable = Variable("blog.articles.0.author.name")
-      let result = try variable.resolve(context) as? Int
+      let result = try variable.resolve(self.context) as? String
+      try expect(result) == "Kyle"
+    }
+
+    it("can resolve a superclass value via reflection") {
+      let variable = Variable("blog.url")
+      let result = try variable.resolve(self.context) as? String
+      try expect(result) == "blog.com"
+    }
+
+    it("can resolve optional variable property using reflection") {
+      let variable = Variable("blog.featuring.author.name")
+      let result = try variable.resolve(self.context) as? String
+      try expect(result) == "Jhon"
+    }
+  }
+
+  func testKVO() {
+    #if os(OSX)
+    it("can resolve a value via KVO") {
+      let variable = Variable("object.title")
+      let result = try variable.resolve(self.context) as? String
+      try expect(result) == "Hello World"
+    }
+
+    it("can resolve a superclass value via KVO") {
+      let variable = Variable("object.name")
+      let result = try variable.resolve(self.context) as? String
+      try expect(result) == "Foo"
+    }
+
+    it("does not crash on KVO") {
+      let variable = Variable("object.fullname")
+      let result = try variable.resolve(self.context) as? String
+      try expect(result).to.beNil()
+    }
+    #endif
+  }
+
+  func testTuple() {
+    it("can resolve tuple by index") {
+      let variable = Variable("tuple.0")
+      let result = try variable.resolve(self.context) as? Int
       try expect(result) == 1
     }
 
-#if os(OSX)
+    it("can resolve tuple by label") {
-    $0.it("can resolve a value via KVO") {
+      let variable = Variable("tuple.two")
-      let variable = Variable("object.title")
+      let result = try variable.resolve(self.context) as? Int
-      let result = try variable.resolve(context) as? String
+      try expect(result) == 2
-      try expect(result) == "Hello World"
+    }
+  }
+
+  func testOptional() {
+    it("does not render Optional") {
+      var array: [Any?] = [1, nil]
+      array.append(array)
+      let context = Context(dictionary: ["values": array])
+
+      try expect(VariableNode(variable: "values").render(context)) == "[1, nil, [1, nil]]"
+      try expect(VariableNode(variable: "values.1").render(context)) == ""
+    }
+  }
+
+  func testSubscripting() {
+    it("can resolve a property subscript via reflection") {
+      try self.context.push(dictionary: ["property": "name"]) {
+        let variable = Variable("article.author[property]")
+        let result = try variable.resolve(self.context) as? String
+        try expect(result) == "Kyle"
+      }
+    }
+
+    it("can subscript an array with a valid index") {
+      try self.context.push(dictionary: ["property": 0]) {
+        let variable = Variable("contacts[property]")
+        let result = try variable.resolve(self.context) as? String
+        try expect(result) == "Katie"
+      }
+    }
+
+    it("can subscript an array with an unknown index") {
+      try self.context.push(dictionary: ["property": 5]) {
+        let variable = Variable("contacts[property]")
+        let result = try variable.resolve(self.context) as? String
+        try expect(result).to.beNil()
+      }
+    }
+
+    #if os(OSX)
+    it("can resolve a subscript via KVO") {
+      try self.context.push(dictionary: ["property": "name"]) {
+        let variable = Variable("object[property]")
+        let result = try variable.resolve(self.context) as? String
+        try expect(result) == "Foo"
+      }
+    }
+    #endif
+
+    it("can resolve an optional subscript via reflection") {
+      try self.context.push(dictionary: ["property": "featuring"]) {
+        let variable = Variable("blog[property].author.name")
+        let result = try variable.resolve(self.context) as? String
+        try expect(result) == "Jhon"
+      }
+    }
+  }
+
+  func testMultipleSubscripting() {
+    it("can resolve multiple subscripts") {
+      try self.context.push(dictionary: [
+        "prop1": "articles",
+        "prop2": 0,
+        "prop3": "name"
+      ]) {
+        let variable = Variable("blog[prop1][prop2].author[prop3]")
+        let result = try variable.resolve(self.context) as? String
+        try expect(result) == "Kyle"
+      }
+    }
+
+    it("can resolve nested subscripts") {
+      try self.context.push(dictionary: [
+        "prop1": "prop2",
+        "ref": ["prop2": "name"]
+      ]) {
+        let variable = Variable("article.author[ref[prop1]]")
+        let result = try variable.resolve(self.context) as? String
+        try expect(result) == "Kyle"
+      }
+    }
+
+    it("throws for invalid keypath syntax") {
+      try self.context.push(dictionary: ["prop": "name"]) {
+        let samples = [
+          ".",
+          "..",
+          ".test",
+          "test..test",
+          "[prop]",
+          "article.author[prop",
+          "article.author[[prop]",
+          "article.author[prop]]",
+          "article.author[]",
+          "article.author[[]]",
+          "article.author[prop][]",
+          "article.author[prop]comments",
+          "article.author[.]"
+        ]
+
+        for lookup in samples {
+          let variable = Variable(lookup)
+          try expect(variable.resolve(self.context)).toThrow()
+        }
+      }
+    }
+  }
+
+  func testRangeVariable() {
+    func makeVariable(_ token: String) throws -> RangeVariable? {
+      let token = Token.variable(value: token, at: .unknown)
+      return try RangeVariable(token.contents, environment: context.environment, containedIn: token)
+    }
+
+    it("can resolve closed range as array") {
+      let result = try makeVariable("1...3")?.resolve(self.context) as? [Int]
+      try expect(result) == [1, 2, 3]
+    }
+
+    it("can resolve decreasing closed range as reversed array") {
+      let result = try makeVariable("3...1")?.resolve(self.context) as? [Int]
+      try expect(result) == [3, 2, 1]
+    }
+
+    it("can use filter on range variables") {
+      let result = try makeVariable("1|incr...3|incr")?.resolve(self.context) as? [Int]
+      try expect(result) == [2, 3, 4]
+    }
+
+    it("throws when left value is not int") {
+      let template: Template = "{% for i in k...j %}{{ i }}{% endfor %}"
+      try expect(try template.render(Context(dictionary: ["j": 3, "k": "1"]))).toThrow()
+    }
+
+    it("throws when right value is not int") {
+      let variable = try makeVariable("k...j")
+      try expect(try variable?.resolve(Context(dictionary: ["j": "3", "k": 1]))).toThrow()
+    }
+
+    it("throws is left range value is missing") {
+      try expect(makeVariable("...1")).toThrow()
+    }
+
+    it("throws is right range value is missing") {
+      try expect(makeVariable("1...")).toThrow()
     }
-#endif
   }
 }
+
+// MARK: - Helpers
+
+#if os(OSX)
+@objc
+class Superclass: NSObject {
+  @objc let name = "Foo"
+}
+@objc
+class Object: Superclass {
+  @objc let title = "Hello World"
+}
+#endif
+
+private struct Person {
+  let name: String
+}
+
+private struct Article {
+  let author: Person
+}
+
+private class WebSite {
+  let url: String = "blog.com"
+}
+
+private class Blog: WebSite {
+  let articles: [Article] = [Article(author: Person(name: "Kyle"))]
+  let featuring: Article? = Article(author: Person(name: "Jhon"))
+}
+
+@dynamicMemberLookup
+private struct DynamicStruct: DynamicMemberLookup {
+  subscript(dynamicMember member: String) -> Any? {
+    member == "test" ? "this is a dynamic response" : nil
+  }
+}
+
+private enum DynamicEnum: String, DynamicMemberLookup {
+  case someValue = "this is raw value"
+}

Tests/StencilTests/XCTest.swift

@@ -1,30 +0,0 @@
-import XCTest
-
-
-public func stencilTests() {
-  testContext()
-  testFilter()
-  testLexer()
-  testToken()
-  testTokenParser()
-  testTemplateLoader()
-  testTemplate()
-  testVariable()
-  testNode()
-  testForNode()
-  testExpressions()
-  testIfNode()
-  testNowNode()
-  testInclude()
-  testInheritence()
-  testFilterTag()
-  testEnvironment()
-  testStencil()
-}
-
-
-class StencilTests: XCTestCase {
-  func testRunStencilTests() {
-    stencilTests()
-  }
-}

Tests/StencilTests/fixtures/base-repeat.html

@@ -0,0 +1,5 @@
+{% block header %}Header{% endblock %}
+{% block body %}Body{% endblock %}
+Repeat
+{{ block.header }}
+{{ block.body }}

Tests/StencilTests/fixtures/child-child.html

@@ -1,2 +1,2 @@
 {% extends "child.html" %}
-{% block header %}Child Child Header{% endblock %}
+{% block header %}{{ block.super }} Child_Child_Header{% endblock %}

Tests/StencilTests/fixtures/child-repeat.html

@@ -0,0 +1,3 @@
+{% extends "base-repeat.html" %}
+{% block header %}Super_{{ block.super }} Child_Header{% endblock %}
+{% block body %}Child_Body{% endblock %}

Tests/StencilTests/fixtures/child-super.html

@@ -1,3 +1,3 @@
 {% extends "base.html" %}
-{% block body %}Child {{ block.super }}{% endblock %}
+{% block body %}Child_{{ block.super }}{% endblock %}
 

Tests/StencilTests/fixtures/child.html

@@ -1,2 +1,3 @@
 {% extends "base.html" %}
-{% block body %}Child{% endblock %}
+{% block header %}Super_{{ block.super }} Child_Header{% endblock %}
+{% block body %}Child_Body{% endblock %}

Tests/StencilTests/fixtures/if-block-child.html

@@ -0,0 +1,2 @@
+{% extends "if-block.html" %}
+{% block title %}{% if sort == "new" %}{{ block.super }} - Nieuwste spellen{% elif sort == "upcoming" %}{{ block.super }} - Binnenkort op de agenda{% elif sort == "near-me" %}{{ block.super }} - In mijn buurt{% endif %}{% endblock %}

Tests/StencilTests/fixtures/if-block.html

@@ -0,0 +1 @@
+{% block title %}Title{% endblock %}

Tests/StencilTests/fixtures/invalid-base.html

@@ -0,0 +1,2 @@
+{% block header %}Header{% endblock %}
+{% block body %}Body {{ target|unknown }} {% endblock %}

Tests/StencilTests/fixtures/invalid-child-super.html

@@ -0,0 +1,3 @@
+{% extends "invalid-base.html" %}
+{% block body %}Child {{ block.super }}{% endblock %}
+

Tests/StencilTests/fixtures/invalid-include.html

@@ -0,0 +1 @@
+Hello {{ target|unknown }}!

docs/_templates/sidebar_intro.html

@@ -2,7 +2,7 @@
 
 <p>
   <iframe
-      src="https://ghbtns.com/github-btn.html?user=kylef&repo=Stencil&type=watch&count=true&size=large"
+      src="https://ghbtns.com/github-btn.html?user=stencilproject&repo=Stencil&type=watch&count=true&size=large"
       allowtransparency="true" frameborder="0" scrolling="0" width="200px" height="35px">
   </iframe>
 </p>

docs/builtins.rst

@@ -28,9 +28,20 @@ The ``for`` tag can iterate over dictionaries.
         <li>{{ key }}: {{ value }}</li>
       {% endfor %}
     </ul>
+    
+It can also iterate over ranges, tuple elements, structs' and classes' stored properties (using ``Mirror``).
 
-The ``for`` tag can contain optional ``where`` expression to filter out
+You can iterate over range literals created using ``N...M`` syntax, both in ascending and descending order:
-elements on which this expression evaluates to false.
+
+.. code-block:: html+django
+
+    <ul>
+      {% for i in 1...array.count %}
+        <li>{{ i }}</li>
+      {% endfor %}
+    </ul>
+
+The ``for`` tag can contain optional ``where`` expression to filter out elements on which this expression evaluates to false.
 
 .. code-block:: html+django
 
@@ -40,8 +51,7 @@ elements on which this expression evaluates to false.
       {% endfor %}
     </ul>
 
-The ``for`` tag can take an optional ``{% empty %}`` block that will be
+The ``for`` tag can take an optional ``{% empty %}`` block that will be displayed if the given list is empty or could not be found.
-displayed if the given list is empty or could not be found.
 
 .. code-block:: html+django
 
@@ -59,6 +69,7 @@ The for block sets a few variables available within the loop:
 - ``last`` - True if this is the last time through the loop
 - ``counter`` - The current iteration of the loop (1 indexed)
 - ``counter0`` - The current iteration of the loop (0 indexed)
+- ``length`` - The total length of the loop
 
 For example:
 
@@ -76,12 +87,74 @@ For example:
       This is user number {{ forloop.counter }} user.
     {% endfor %}
 
+The ``for`` tag accepts an optional label, so that it may later be referred to by name. The contexts of parent labeled loops can be accessed via the `forloop` property:
+
+.. code-block:: html+django
+
+    {% outer: for item in users %}
+      {% for item in 1..3 %}
+        {% if forloop.outer.first %}
+          This is the first user.
+        {% endif %}
+      {% endfor %}
+    {% endfor %}
+
+``break``
+~~~~~~~~~
+
+The ``break`` tag lets you jump out of a for loop, for example if a certain condition is met:
+
+.. code-block:: html+django
+
+    {% for user in users %}
+      {% if user.inaccessible %}
+        {% break %}
+      {% endif %}
+      This is user {{ user.name }}.
+    {% endfor %}
+
+Break tags accept an optional label parameter, so that you may break out of multiple loops:
+
+.. code-block:: html+django
+
+    {% outer: for user in users %}
+      {% for address in user.addresses %}
+        {% if address.isInvalid %}
+          {% break outer %}
+        {% endif %}
+      {% endfor %}
+    {% endfor %}
+
+``continue``
+~~~~~~~~~
+
+The ``continue`` tag lets you skip the rest of the blocks in a loop, for example if a certain condition is met:
+
+.. code-block:: html+django
+
+    {% for user in users %}
+      {% if user.inaccessible %}
+        {% continue %}
+      {% endif %}
+      This is user {{ user.name }}.
+    {% endfor %}
+
+Continue tags accept an optional label parameter, so that you may skip the execution of multiple loops:
+
+.. code-block:: html+django
+
+    {% outer: for user in users %}
+      {% for address in user.addresses %}
+        {% if address.isInvalid %}
+          {% continue outer %}
+        {% endif %}
+      {% endfor %}
+    {% endfor %}
 
 ``if``
 ~~~~~~
 
-The ``{% if %}`` tag evaluates a variable, and if that variable evaluates to
+The ``{% if %}`` tag evaluates a variable, and if that variable evaluates to true the contents of the block are processed. Being true is defined as:
-true the contents of the block are processed. Being true is defined as:
 
 * Present in the context
 * Being non-empty (dictionaries or arrays)
@@ -102,8 +175,7 @@ true the contents of the block are processed. Being true is defined as:
 Operators
 ^^^^^^^^^
 
-``if`` tags may combine ``and``, ``or`` and ``not`` to test multiple variables
+``if`` tags may combine ``and``, ``or`` and ``not`` to test multiple variables or to negate a variable.
-or to negate a variable.
 
 .. code-block:: html+django
 
@@ -124,7 +196,7 @@ or to negate a variable.
     {% endif %}
 
 You may use ``and``, ``or`` and ``not`` multiple times together. ``not`` has
-higest prescidence followed by ``and``. For example:
+higest precedence followed by ``and``. For example:
 
 .. code-block:: html+django
 
@@ -136,6 +208,19 @@ Will be treated as:
 
     one or (two and three)
 
+You can use parentheses to change operator precedence. For example:
+
+.. code-block:: html+django
+
+    {% if (one or two) and three %}
+
+Will be treated as:
+
+.. code-block:: text
+
+    (one or two) and three
+
+
 ``==`` operator
 """""""""""""""
 
@@ -247,8 +332,13 @@ You can include another template using the `include` tag.
 
     {% include "comment.html" %}
 
-The `include` tag requires you to provide a loader which will be used to lookup
+By default the included file gets passed the current context. You can pass a sub context by using an optional 2nd parameter as a lookup in the current context.
-the template.
+
+.. code-block:: html+django
+
+    {% include "comment.html" comment %}
+
+The `include` tag requires you to provide a loader which will be used to lookup the template.
 
 .. code-block:: swift
 
@@ -269,8 +359,7 @@ See :ref:`template-inheritance` for more information.
 ``block``
 ~~~~~~~~~
 
-Defines a block that can be overridden by child templates. See
+Defines a block that can be overridden by child templates. See :ref:`template-inheritance` for more information.
-:ref:`template-inheritance` for more information.
 
 .. _built-in-filters:
 
@@ -280,8 +369,7 @@ Built-in Filters
 ``capitalize``
 ~~~~~~~~~~~~~~
 
-The capitalize filter allows you to capitalize a string.
+The capitalize filter allows you to capitalize a string. For example, `stencil` to `Stencil`. Can be applied to array of strings to change each string.
-For example, `stencil` to `Stencil`.
 
 .. code-block:: html+django
 
@@ -290,8 +378,7 @@ For example, `stencil` to `Stencil`.
 ``uppercase``
 ~~~~~~~~~~~~~
 
-The uppercase filter allows you to transform a string to uppercase.
+The uppercase filter allows you to transform a string to uppercase. For example, `Stencil` to `STENCIL`. Can be applied to array of strings to change each string.
-For example, `Stencil` to `STENCIL`.
 
 .. code-block:: html+django
 
@@ -300,8 +387,7 @@ For example, `Stencil` to `STENCIL`.
 ``lowercase``
 ~~~~~~~~~~~~~
 
-The uppercase filter allows you to transform a string to lowercase.
+The uppercase filter allows you to transform a string to lowercase. For example, `Stencil` to `stencil`. Can be applied to array of strings to change each string.
-For example, `Stencil` to `stencil`.
 
 .. code-block:: html+django
 
@@ -310,8 +396,7 @@ For example, `Stencil` to `stencil`.
 ``default``
 ~~~~~~~~~~~
 
-If a variable not present in the context, use given default. Otherwise, use the
+If a variable not present in the context, use given default. Otherwise, use the value of the variable. For example:
-value of the variable. For example:
 
 .. code-block:: html+django
 
@@ -326,4 +411,41 @@ Join an array of items.
 
     {{ value|join:", " }}
 
-.. note:: The value MUST be an array.
+.. note:: The value MUST be an array. Default argument value is empty string.
+
+``split``
+~~~~~~~~~
+
+Split string into substrings by separator.
+
+.. code-block:: html+django
+
+    {{ value|split:", " }}
+
+.. note:: The value MUST be a String. Default argument value is a single-space string.
+
+``indent``
+~~~~~~~~~
+
+Indents lines of rendered value or block.
+
+.. code-block:: html+django
+
+    {{ value|indent:2," ",true }}
+
+Filter accepts several arguments:
+
+* indentation width: number of indentation characters to indent lines with. Default is ``4``.
+* indentation character: character to be used for indentation. Default is a space.
+* indent first line: whether first line of output should be indented or not. Default is ``false``.
+
+``filter``
+~~~~~~~~~
+
+Applies the filter with the name provided as an argument to the current expression.
+
+.. code-block:: html+django
+
+    {{ string|filter:myfilter }}
+
+This expression will resolve the `myfilter` variable, find a filter named the same as resolved value, and will apply it to the `string` variable. I.e. if `myfilter` variable resolves to string `uppercase` this expression will apply file `uppercase` to `string` variable.

docs/conf.py

@@ -50,7 +50,7 @@ master_doc = 'index'
 
 # General information about the project.
 project = 'Stencil'
-copyright = '2016, Kyle Fuller'
+copyright = '2022, Kyle Fuller'
 author = 'Kyle Fuller'
 
 # The version info for the project you're documenting, acts as replacement for
@@ -58,9 +58,9 @@ author = 'Kyle Fuller'
 # built documents.
 #
 # The short X.Y version.
-version = '0.7.0'
+version = '0.15.1'
 # The full version, including alpha/beta/rc tags.
-release = '0.7.0'
+release = '0.15.1'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.

docs/custom-template-tags-and-filters.rst

@@ -48,6 +48,17 @@ Registering custom filters with arguments:
       return value
     }
 
+Registering custom boolean filters:
+
+.. code-block:: swift
+
+    ext.registerFilter("ordinary", negativeFilterName: "odd") { (value: Any?) in
+        if let value = value as? Int {
+            return myInt % 2 == 0
+        }
+        return nil
+    }
+
 Custom Tags
 -----------
 

docs/index.rst

@@ -32,7 +32,7 @@ feel right at home with Stencil.
     ]
 
     let environment = Environment(loader: FileSystemLoader(paths: ["templates/"])
-    let rendered = try environment.renderTemplate(name: context)
+    let rendered = try environment.renderTemplate(name: "articles.html", context: context)
 
     print(rendered)
 

docs/installation.rst

@@ -14,7 +14,7 @@ dependencies inside ``Package.swift``.
     let package = Package(
       name: "MyApplication",
       dependencies: [
-        .Package(url: "https://github.com/kylef/Stencil.git", majorVersion: 0, minor: 8),
+        .package(url: "https://github.com/stencilproject/Stencil.git", from: "0.15.1"),
       ]
     )
 
@@ -26,7 +26,7 @@ If you're using CocoaPods, you can add Stencil to your ``Podfile`` and then run
 
 .. code-block:: ruby
 
-    pod 'Stencil', '~> 0.8.0'
+    pod 'Stencil', '~> 0.15.1'
 
 Carthage
 --------
@@ -37,7 +37,7 @@ Carthage
 
     .. code-block:: text
 
-        github "kylef/Stencil" ~> 0.8.0
+        github "stencilproject/Stencil" ~> 0.15.1
 
 2) Checkout your dependencies, generate the Stencil Xcode project, and then use Carthage to build Stencil:
 

docs/templates.rst

@@ -20,9 +20,10 @@ following lookup:
 
 - Context lookup
 - Dictionary lookup
-- Array lookup (first, last, count, index)
+- Array and string lookup (first, last, count, by index)
 - Key value coding lookup
-- Type introspection
+- @dynamicMemberLookup when conforming to our `DynamicMemberLookup` marker protocol
+- Type introspection (via ``Mirror``)
 
 For example, if `people` was an array:
 
@@ -31,6 +32,42 @@ For example, if `people` was an array:
     There are {{ people.count }} people. {{ people.first }} is the first
     person, followed by {{ people.1 }}.
 
+You can also use the subscript operator for indirect evaluation. The expression
+between brackets will be evaluated first, before the actual lookup will happen.
+
+For example, if you have the following context:
+
+.. code-block:: swift
+
+    [
+      "item": [
+        "name": "John"
+      ],
+      "key": "name"
+    ]
+
+.. code-block:: html+django
+
+    The result of {{ item[key] }} will be the same as {{ item.name }}. It will first evaluate the result of {{ key }}, and only then evaluate the lookup expression.
+
+You can use the `LazyValueWrapper` type to have values in your context that will be lazily evaluated. The provided value will only be evaluated when it's first accessed in your template, and will be cached afterwards. For example:
+
+.. code-block:: swift
+
+    [
+      "magic": LazyValueWrapper(myHeavyCalculations())
+    ]
+
+Boolean expressions
+-------------------
+
+Boolean expressions can be rendered using ``{{ ... }}`` tag.
+For example, this will output string `true` if variable is equal to 1 and `false` otherwise:
+
+.. code-block:: html+django
+
+    {{ variable == 1 }}
+
 Filters
 ~~~~~~~
 
@@ -76,6 +113,17 @@ To comment out part of your template, you can use the following syntax:
 
     {# My comment is completely hidden #}
 
+Whitespace Control
+------------------
+
+Stencil supports the same syntax as Jinja for whitespace control, see `their docs for more information <https://jinja.palletsprojects.com/en/3.1.x/templates/#whitespace-control>`_.
+
+Essentially, Stencil will **not** trim whitespace by default. However you can:
+
+- Control how this is handled for the whole template by setting the trim behaviour. We provide a few pre-made combinations such as `nothing` (default), `smart` and `all`. More granular combinations are possible.
+- You can disable this per-block using the `+` control character. For example `{{+ if … }}` to preserve whitespace before.
+- You can force trimming per-block by using the `-` control character. For example `{{ if … -}}` to trim whitespace after.
+
 .. _template-inheritance:
 
 Template inheritance
@@ -111,7 +159,7 @@ Let's take a look at an example. Here is our base template (``base.html``):
     </html>
 
 This example declares three blocks, ``title``, ``sidebar`` and ``content``. We
-can use the ``{% extends %}`` template tag to inherit from out base template
+can use the ``{% extends %}`` template tag to inherit from our base template
 and then use ``{% block %}`` to override any blocks from our base template.
 
 A child template might look like the following:
@@ -165,3 +213,5 @@ inheritance is the following three-level approach:
   extend ``base.html`` and include section-specific styles/design.
 * Create individual templates for each type of page, such as a news article or
   blog entry. These templates extend the appropriate section template.
+
+You can render block's content more than once by using ``{{ block.name }}`` **after** a block is defined.