Merge pull request #319 from stencilproject/release/0.14.2

Release 0.14.2

.gitignore

@@ -1,3 +1,6 @@
 .conche/
 .build/
+.swiftpm/
 Packages/
+Package.pins
+*.xcodeproj

.swift-version

@@ -1 +0,0 @@
-3.0.1

.swiftlint.yml

@@ -0,0 +1,99 @@
+swiftlint_version: 0.39.2
+
+disabled_rules:
+  # Remove this once we remove old swift support
+  - implicit_return
+
+opt_in_rules:
+  - anyobject_protocol
+  - array_init
+  - attributes
+  - closure_body_length
+  - closure_end_indentation
+  - closure_spacing
+  - collection_alignment
+  - contains_over_filter_count
+  - contains_over_filter_is_empty
+  - contains_over_first_not_nil
+  - contains_over_range_nil_comparison
+  - convenience_type
+  - discouraged_optional_boolean
+  - discouraged_optional_collection
+  - duplicate_enum_cases
+  - duplicate_imports
+  - empty_collection_literal
+  - empty_count
+  - empty_string
+  - fallthrough
+  - fatal_error_message
+  - first_where
+  - flatmap_over_map_reduce
+  - force_unwrapping
+  - identical_operands
+  - inert_defer
+  - joined_default_parameter
+  - last_where
+  - legacy_hashing
+  - legacy_random
+  - literal_expression_end_indentation
+  - lower_acl_than_parent
+  - modifier_order
+  - multiline_arguments
+  - multiline_function_chains
+  - multiline_literal_brackets
+  - multiline_parameters
+  - multiline_parameters_brackets
+  - nslocalizedstring_key
+  - nsobject_prefer_isequal
+  - number_separator
+  - object_literal
+  - operator_usage_whitespace
+  - overridden_super_call
+  - override_in_extension
+  - prefer_self_type_over_type_of_self
+  - private_action
+  - private_outlet
+  - prohibited_super_call
+  - raw_value_for_camel_cased_codable_enum
+  - reduce_boolean
+  - reduce_into
+  - redundant_nil_coalescing
+  - redundant_objc_attribute
+  - sorted_first_last
+  - sorted_imports
+  - static_operator
+  - strong_iboutlet
+  - toggle_bool
+  - trailing_closure
+  - unavailable_function
+  - unneeded_parentheses_in_closure_argument
+  - unowned_variable_capture
+  - unused_capture_list
+  - unused_control_flow_label
+  - unused_declaration
+  - unused_setter_value
+  - vertical_parameter_alignment_on_call
+  - vertical_whitespace_closing_braces
+  - vertical_whitespace_opening_braces
+  - xct_specific_matcher
+  - yoda_condition
+  # Enable this again once we remove old swift support
+  # - optional_enum_case_matching
+  # - legacy_multiple
+
+# Rules customization
+closure_body_length:
+  warning: 25
+
+line_length:
+  warning: 120
+  error: 200
+
+nesting:
+  type_level:
+    warning: 2
+
+# Exclude generated files
+excluded:
+  - .build
+  - Tests/StencilTests/XCTestManifests.swift

.travis.yml

@@ -1,11 +1,22 @@
-os:
-- osx
-- linux
+matrix:
+  include:
+    - os: osx
+      osx_image: xcode11.4
+      env: SWIFT_VERSION=4.2
+    - os: osx
+      osx_image: xcode11.4
+      env: SWIFT_VERSION=5.0
+    - os: linux
+      env: SWIFT_VERSION=4.2
+    - os: linux
+      env: SWIFT_VERSION=5.0
 language: generic
 sudo: required
 dist: trusty
-osx_image: xcode8
 install:
-- eval "$(curl -sL https://gist.githubusercontent.com/kylef/5c0475ff02b7c7671d2a/raw/9f442512a46d7a2af7b850d65a7e9bd31edfb09b/swiftenv-install.sh)"
+  - if [ "$TRAVIS_OS_NAME" == "linux" ]; then eval "$(curl -sL https://swiftenv.fuller.li/install.sh)"; fi
+  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then wget --output-document /tmp/SwiftLint.pkg https://github.com/realm/SwiftLint/releases/download/0.39.2/SwiftLint.pkg &&
+    sudo installer -pkg /tmp/SwiftLint.pkg -target /; fi
 script:
-- swift test
+  - swift test
+  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then swiftlint; fi

ARCHITECTURE.md

@@ -1,175 +0,0 @@
-Stencil Architecture
-====================
-
-This document outlines the architecture of Stencil and how it works internally.
-
-Stencil uses a three-step process for rendering templates. The first step is tokenising the template into an array of Token’s. Afterwards, the array of token’s are transformed into a collection of Node’s. Once we have a collection of Node’s (objects conforming to the `Node` protocol), we then call `render(context)` on each Node instructing it to render itself inside the given context.
-
-## Token
-
-Token is an enum which has four members. These represent a piece of text, a variable, a comment or a template block. They are parsed using the `TokenParser` which takes the template as a string as input and returns an array of Token’s.
-
-### Values
-
-#### Text
-
-A text token represents a string which will be rendered in the template. For example, a text token with the string `Hello World` will be rendered as such in the output.
-
-#### Variable
-
-A variable token represents a variable inside a context. It will be evaluated and rendered in the output. It is created from the template using `{{ string }}`.
-
-#### Comment
-
-The comment token represents a comment inside the source. It is created using `{# This is a comment #}`.
-
-#### Block
-
-A block represents a template tag. It is created using `{% this is a template block %}` inside a template. The template tag in this case would be called `this`. See “Block Token” below for more information.
-
-### Parsing
-
-A template is parsed using the TokenParser into an array of Token’s. For example:
-
-```html+django
-Hello {{ name }}
-```
-
-Would be parsed into two tokens. A token representing the string, `Hello ` and a token representing the variable called `name`. So, in Swift it would be represented as follows:
-
-```swift
-let tokens = [
-  Token.Text("Hello "),
-  Token.Variable("name"),
-]
-```
-
-## Node
-
-Node is a protocol with a single method, to render it inside a context. When rendering a node, it is converted into the output string, or an error if there is a failure. Token’s are converted to Node’s using the `TokenParser` class.
-
-For some Token’s, there is a direct mapping from a Token to a Node. However block node’s do not have a 1:1 mapping.
-
-### Token Parsing
-
-#### Text Token
-
-A text token is converted directly to a `TextNode` which simply returns the text when rendered.
-
-#### Variable Token
-
-Variable Token’s are transformed directly to a `VariableNode`, which will evaluate a variable in the given template when rendered.
-
-#### Comment Token
-
-A comment token is simply omitted, a comment token will be dropped when it is converted to a Node.
-
-#### Block Token
-
-Block token’s are slightly different from the other tokens, there is no direct mapping. A block token is made up of a string representing the token. For example `now` or `for article in articles`. The `TokenParser` will pull out the first word inside the string representation and use that to look-up a parser for the block. So, in this example, the template tag names will be `now` or `for`.
-
-The template tag’s are registered with a block of code which deals with the parsing for the given tag. This allows the parser to parse a set of tokens ahead of the block tone. This is useful for control flow, such as the `for` template tag will want to parse any following tokens up until the `endblock` block token.
-
-For example:
-
-```html+django
-{% for article in articles %}
-  An Article
-{% endfor %}
-```
-
-Or as a set of tokens:
-
-```swift
-let tokens = [
-  Token.Block("for article in articles"),
-  Token.Text("  An Article")
-  Token.Block("endfor")
-]
-```
-
-Will result in a single Node (a `ForNode`) which contains the sub-node containing the text. The `ForNode` class has a property called `forNodes` which contains the text node representing the text token (`  An Article`).
-
-When the `ForNode` is rendered in a context, it will look up the variable `articles` and if it’s an array it will loop over it. Inserting the variable `article` into the context while rendered the `forNodes` for each article.
-
-### Custom Nodes
-
-There are two ways to register custom template tags. A simple way which allows you to map 1:1 a block token to a Node. You can also register a more advanced template tag which has it’s own block of code for handling parsing if you want to parse up until another token such as if you are trying to provide flow-control.
-
-The tags are registered with a `Namespace` passed when rendering your `Template`.
-
-#### Simple Tags
-
-A simple tag is registered with a string for the tag name and a block of code which is evaluated when the block is rendered in a given context.
-
-Here’s an example. Registering a template tag called `custom` which just renders `Hello World` in the rendered template:
-
-```swift
-namespace.registerSimpleTag("custom") { context in
-  return "Hello World"
-}
-```
-
-You would use it as such in a template:
-
-```html+django
-{% custom %}
-```
-
-#### Advanced Tags
-
-If you need more control or functionality than the simple tag’s above, you can use the node based API where you can provide a block of code to deal with parsing. There are a few examples of this in use over at `Node.swift` inside Stencil. There is an implementation of `if` and `for` template tags.
-
-You would register a template tag using the `registerTag` API inside a `Namespace` which accepts a name for the tag and a block of code to handle parsing. The block of code is invoked with the parser and the current token as an argument. This allows you to use the API on `TokenParser` to parse node’s further in the token array.
-
-As an example, we’re going to create a template tag called `debug` which will optionally render nodes from `debug` up until `enddebug`. When rendering the `DebugNode`, it will only render the nodes inside if a variable called `debug` is set to `true` inside the template Context.
-
-```html+django
-{% debug %}
-  Debugging is enabled!
-{% enddebug %}
-```
-
-This will be represented by a `DebugNode` which will have a property containing all of the Node’s inside the `debug`/`enddebug` block. In the above example, this will just be a TextNode containing `  Debugging is enabled!`.
-
-When the `DebugNode` is rendered, it will determine if debug is enabled by introspecting the context and if it is enabled. We will render the nodes, otherwise just return an empty string to hide the debug output.
-
-So, our `DebugNode` would look like as following:
-
-```swift
-class DebugNode : Node {
-  let nodes:[Node]
-
-  init(nodes:[Node]) {
-    self.nodes = nodes
-  }
-
-  func render(context: Context) throws -> String {
-    // Is there a debug variable inside the context?
-    if let debug = context["debug"] as? Bool {
-      // Is debug set to true?
-      if debug {
-        // Let's render the given nodes in the context since debug is enabled.
-        return renderNodes(nodes, context)
-      }
-    }
-
-    // Debug is turned off, so let's not render anything
-    return ""
-  }
-}
-```
-
-We will need to write a parser to parse up until the `enddebug` template block and create a `DebugNode` with the nodes in-between. If there was another error form another Node inside, then we will return that error.
-
-```swift
-namespace.registerTag("debug") { parser, token in
-  // Use the parser to parse every token up until the `enddebug` block.
-  let nodes = try until(["enddebug"]))
-  return DebugNode(nodes)
-}
-```
-
-## Context
-
-A Context is a structure containing any templates you would like to use in a template. It’s somewhat like a dictionary, however you can push and pop to scope variables. So that means that when iterating over a for loop, you can push a new scope into the context to store any variables local to the scope.

CHANGELOG.md

@@ -1,4 +1,352 @@
-# Stencil Changelog
+## 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)
+  [#172](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
+
+### Enhancements
+
+- Add support for Xcode 9.1.
+
+## 0.10.0
+
+### Enhancements
+
+- Adds `counter0` to for loop context allowing you to get the current index of
+  the for loop 0 indexed.
+- Introduces a new `DictionaryLoader` for loading templates from a Swift
+  Dictionary.
+- Added `in` expression in if tag for strings and arrays of hashable types
+- You can now access the amount of items in a dictionary using the `count`
+  property.
+
+### Bug Fixes
+
+- Fixes a potential crash when using the `{% for %}` template tag with the
+  incorrect amount of arguments.
+- Fixes a potential crash when using incomplete tokens in a template for
+  example, `{%%}` or `{{}}`.
+- Fixes evaluating nil properties as true
+
+
+## 0.9.0
+
+### Enhancements
+
+- `for` block now can contain `where` expression to filter array items. For example `{% for item in items where item > 1 %}` is now supported.
+- `if` blocks may now contain else if (`elif`) conditions.
+
+  ```html+django
+  {% if one or two and not three %}
+    one or two but not three
+  {% elif four %}
+    four
+  {% else %}
+    not one, two, or four
+  {% endif %}
+  ```
+
+- `for` block now allows you to iterate over array of tuples or dictionaries.
+
+  ```html+django
+  {% for key,value in thing %}
+    <li>{{ key }}: {{ value }}</li>
+  {% endfor %}
+  ```
+
+### Bug Fixes
+
+- You can now use literal filter arguments which contain quotes.
+  [#98](https://github.com/kylef/Stencil/pull/98)
+
+
+## 0.8.0
+
+### Breaking
+
+- It is no longer possible to create `Context` objects. Instead, you can pass a
+  dictionary directly to a `Template`s `render` method.
+
+  ```diff
+  - try template.render(Context(dictionary: ["name": "Kyle"]))
+  + try template.render(["name": "Kyle"])
+  ```
+
+- Template loader are no longer passed into a `Context`, instead you will need
+  to pass the `Loader` to an `Environment` and create a template from the
+  `Environment`.
+
+  ```diff
+  let loader = FileSystemLoader(paths: ["templates/"])
+
+  - let template = loader.loadTemplate(name: "index.html")
+  - try template.render(Context(dictionary: ["loader": loader]))
+  + let environment = Environment(loader: loader)
+  + try environment.renderTemplate(name: "index.html")
+  ```
+
+- `Loader`s will now throw a `TemplateDoesNotExist` error when a template
+  is not found.
+
+- `Namespace` has been removed and replaced by extensions. You can create an
+  extension including any custom template tags and filters. A collection of
+  extensions can be passed to an `Environment`.
+
+### Enhancements
+
+- `Environment` is a new way to load templates. You can configure an
+  environment with custom template filters, tags and loaders and then create a
+  template from an environment.
+
+  Environment also provides a convenience method to render a template directly.
+
+- `FileSystemLoader` will now ensure that template paths are within the base
+  path. Any template names that try to escape the base path will raise a
+  `SuspiciousFileOperation` error.
+
+- New `{% filter %}` tag allowing you to perform a filter across the contents
+  of a block.
+
+  ```html+django
+  {% filter lowercase %}
+    This Text Will Be Lowercased.
+  {% endfilter %}
+  ```
+
+- You can now use `{{ block.super }}` to render a super block from another `{%
+  block %}`.
+
+- `Environment` allows you to provide a custom `Template` subclass, allowing
+  new template to use a specific subclass.
+
+- If expressions may now contain filters on variables. For example
+  `{% if name|uppercase == "TEST" %}` is now supported.
+
+### Deprecations
+
+- `Template` initialisers have been deprecated in favour of using a template
+  loader such as `FileSystemLoader` inside an `Environment`.
+
+- The use of whitespace inside variable filter expression is now deprecated.
+
+  ```diff
+  - {{ name | uppercase }}
+  + {{ name|uppercase }}
+  ```
+
+### Bug Fixes
+
+- Restores compatibility with ARM based platforms such as iOS. Stencil 0.7
+  introduced compilation errors due to using the `Float80` type which is not
+  available.
+
 
 ## 0.7.1
 
@@ -59,10 +407,10 @@
 ### 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)
 
-- 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)
 
 - If comparisons will now treat 0 and below numbers as negative.

Gemfile

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+gem "octokit"
+gem "cocoapods"
+gem "rake"

Gemfile.lock

@@ -0,0 +1,127 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    CFPropertyList (3.0.4)
+      rexml
+    activesupport (6.1.4.1)
+      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)
+    atomos (0.1.3)
+    claide (1.0.3)
+    cocoapods (1.11.2)
+      addressable (~> 2.8)
+      claide (>= 1.0.2, < 2.0)
+      cocoapods-core (= 1.11.2)
+      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 (1.11.2)
+      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 (1.5.1)
+    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 (1.1.9)
+    escape (0.0.4)
+    ethon (0.15.0)
+      ffi (>= 1.15.0)
+    faraday (1.8.0)
+      faraday-em_http (~> 1.0)
+      faraday-em_synchrony (~> 1.0)
+      faraday-excon (~> 1.1)
+      faraday-httpclient (~> 1.0.1)
+      faraday-net_http (~> 1.0)
+      faraday-net_http_persistent (~> 1.1)
+      faraday-patron (~> 1.0)
+      faraday-rack (~> 1.0)
+      multipart-post (>= 1.2, < 3)
+      ruby2_keywords (>= 0.0.4)
+    faraday-em_http (1.0.0)
+    faraday-em_synchrony (1.0.0)
+    faraday-excon (1.1.0)
+    faraday-httpclient (1.0.1)
+    faraday-net_http (1.0.1)
+    faraday-net_http_persistent (1.2.0)
+    faraday-patron (1.0.0)
+    faraday-rack (1.0.0)
+    ffi (1.15.4)
+    fourflusher (2.3.1)
+    fuzzy_match (2.0.4)
+    gh_inspector (1.1.3)
+    httpclient (2.8.3)
+    i18n (1.8.11)
+      concurrent-ruby (~> 1.0)
+    json (2.6.1)
+    minitest (5.14.4)
+    molinillo (0.8.0)
+    multipart-post (2.1.1)
+    nanaimo (0.3.0)
+    nap (1.1.0)
+    netrc (0.11.0)
+    octokit (4.21.0)
+      faraday (>= 0.9)
+      sawyer (~> 0.8.0, >= 0.5.3)
+    public_suffix (4.0.6)
+    rake (13.0.6)
+    rexml (3.2.5)
+    ruby-macho (2.5.1)
+    ruby2_keywords (0.0.5)
+    sawyer (0.8.2)
+      addressable (>= 2.3.5)
+      faraday (> 0.8, < 2.0)
+    typhoeus (1.4.0)
+      ethon (>= 0.9.0)
+    tzinfo (2.0.4)
+      concurrent-ruby (~> 1.0)
+    xcodeproj (1.21.0)
+      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)
+    zeitwerk (2.5.1)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  cocoapods
+  octokit
+  rake
+
+BUNDLED WITH
+   2.1.4

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2014, Kyle Fuller
+Copyright (c) 2018, 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:4.2
 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: 7),
-
-    // https://github.com/apple/swift-package-manager/pull/597
-    .Package(url: "https://github.com/kylef/Spectre", majorVersion: 0, minor: 7),
-  ]
+    .package(url: "https://github.com/kylef/PathKit.git", from: "1.0.1"),
+    .package(url: "https://github.com/kylef/Spectre.git", from: "0.10.1")
+  ],
+  targets: [
+    .target(name: "Stencil", dependencies: [
+      "PathKit"
+    ], path: "Sources"),
+    .testTarget(name: "StencilTests", dependencies: [
+      "Stencil",
+      "Spectre"
+    ])
+  ],
+  swiftLanguageVersions: [.v4_2]
 )

Package@swift-5.swift

@@ -0,0 +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", from: "1.0.1"),
+    .package(url: "https://github.com/kylef/Spectre.git", from: "0.10.1")
+  ],
+  targets: [
+    .target(name: "Stencil", dependencies: [
+      "PathKit"
+    ], path: "Sources"),
+    .testTarget(name: "StencilTests", dependencies: [
+      "Stencil",
+      "Spectre"
+    ])
+  ],
+  swiftLanguageVersions: [.v4_2, .v5]
+)

README.md

@@ -1,6 +1,6 @@
 # Stencil
 
-[![Build Status](https://travis-ci.org/kylef/Stencil.svg?branch=master)](https://travis-ci.org/kylef/Stencil)
+[![Build Status](https://travis-ci.org/stencilproject/Stencil.svg?branch=master)](https://travis-ci.org/stencilproject/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
@@ -19,35 +19,24 @@ There are {{ articles.count }} articles.
 ```
 
 ```swift
+import Stencil
+
 struct Article {
   let title: String
   let author: String
 }
 
-let context = Context(dictionary: [
+let context = [
   "articles": [
     Article(title: "Migrating from OCUnit to XCTest", author: "Kyle Fuller"),
     Article(title: "Memory Management with ARC", author: "Kyle Fuller"),
   ]
-])
+]
 
-do {
-  let template = try Template(named: "template.html")
-  let rendered = try template.render(context)
-  print(rendered)
-} catch {
-  print("Failed to render template \(error)")
-}
-```
+let environment = Environment(loader: FileSystemLoader(paths: ["templates/"]))
+let rendered = try environment.renderTemplate(name: "article_list.html", context: context)
 
-## Installation
-
-Installation with Swift Package Manager is recommended.
-
-### CocoaPods
-
-```ruby
-pod 'Stencil'
+print(rendered)
 ```
 
 ## Philosophy
@@ -62,10 +51,26 @@ Stencil follows the same philosophy of Django:
 
 ## The User Guide
 
-- [Templates](http://stencil.fuller.li/en/latest/templates.html)
+Resources for Stencil template authors to write Stencil templates:
+
+- [Language overview](http://stencil.fuller.li/en/latest/templates.html)
 - [Built-in template tags and filters](http://stencil.fuller.li/en/latest/builtins.html)
+
+Resources to help you integrate Stencil into a Swift project:
+
+- [Installation](http://stencil.fuller.li/en/latest/installation.html)
+- [Getting Started](http://stencil.fuller.li/en/latest/getting-started.html)
+- [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 +1,10 @@
+
+PODSPEC_FILE = 'Stencil.podspec.json'
+CHANGELOG_FILE = 'CHANGELOG.md'
+
+if ENV['BUNDLE_GEMFILE'].nil?
+  puts "\u{274C} Please use bundle exec"
+  exit 1
+end
+
+task :default => 'release:new'

Sources/Context.swift

@@ -1,17 +1,17 @@
 /// A container for template variables.
 public class Context {
   var dictionaries: [[String: Any?]]
-  let namespace: Namespace
 
-  /// Initialise a Context with an optional dictionary and optional namespace
-  public init(dictionary: [String: Any]? = nil, namespace: Namespace = Namespace()) {
-    if let dictionary = dictionary {
+  public let environment: Environment
+
+  public init(dictionary: [String: Any] = [:], environment: Environment? = nil) {
+    if !dictionary.isEmpty {
       dictionaries = [dictionary]
     } else {
       dictionaries = []
     }
 
-    self.namespace = namespace
+    self.environment = environment ?? Environment()
   }
 
   public subscript(key: String) -> Any? {
@@ -28,26 +28,25 @@ public class Context {
 
     /// 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)
+      if var dictionary = dictionaries.popLast() {
+        dictionary[key] = value
+        dictionaries.append(dictionary)
       }
     }
   }
 
   /// Push a new level into the Context
-  fileprivate func push(_ dictionary: [String: Any]? = nil) {
-    dictionaries.append(dictionary ?? [:])
+  fileprivate func push(_ dictionary: [String: Any] = [:]) {
+    dictionaries.append(dictionary)
   }
 
   /// Pop the last level off of the Context
-  fileprivate func pop() -> [String: Any]? {
+  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 {
+  public func push<Result>(dictionary: [String: Any] = [:], closure: (() throws -> Result)) rethrows -> Result {
     push(dictionary)
     defer { _ = pop() }
     return try closure()

Sources/Environment.swift

@@ -0,0 +1,47 @@
+public struct Environment {
+  public let templateClass: Template.Type
+  public var extensions: [Extension]
+  public var loader: Loader?
+
+  public init(
+    loader: Loader? = nil,
+    extensions: [Extension] = [],
+    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] = [:]) throws -> String {
+    let template = try loadTemplate(name: name)
+    return try render(template: template, context: context)
+  }
+
+  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/Errors.swift

@@ -0,0 +1,81 @@
+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 { return reason }
+  public internal(set) var token: Token?
+  public internal(set) var stackTrace: [Token]
+  public var templateName: String? { return token?.sourceMap.filename }
+  var allTokens: [Token] {
+    return 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/Expression.swift

@@ -1,18 +1,15 @@
-protocol Expression: CustomStringConvertible {
+public protocol Expression: CustomStringConvertible {
   func evaluate(context: Context) throws -> Bool
 }
 
-
 protocol InfixOperator: Expression {
   init(lhs: Expression, rhs: Expression)
 }
 
-
 protocol PrefixOperator: Expression {
   init(expression: Expression)
 }
 
-
 final class StaticExpression: Expression, CustomStringConvertible {
   let value: Bool
 
@@ -29,26 +26,25 @@ final class StaticExpression: Expression, CustomStringConvertible {
   }
 }
 
-
 final class VariableExpression: Expression, CustomStringConvertible {
-  let variable: Variable
+  let variable: Resolvable
 
-  init(variable: Variable) {
+  init(variable: Resolvable) {
     self.variable = variable
   }
 
   var description: String {
-    return "(variable: \(variable.variable))"
+    return "(variable: \(variable))"
   }
 
   /// Resolves a variable in the given context as boolean
-  func resolve(context: Context, variable: Variable) throws -> Bool {
+  func resolve(context: Context, variable: Resolvable) 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
@@ -68,7 +64,6 @@ final class VariableExpression: Expression, CustomStringConvertible {
   }
 }
 
-
 final class NotExpression: Expression, PrefixOperator, CustomStringConvertible {
   let expression: Expression
 
@@ -85,6 +80,40 @@ final class NotExpression: Expression, PrefixOperator, CustomStringConvertible {
   }
 }
 
+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))"
+  }
+
+  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 {
   let lhs: Expression
@@ -109,7 +138,6 @@ final class OrExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 }
 
-
 final class AndExpression: Expression, InfixOperator, CustomStringConvertible {
   let lhs: Expression
   let rhs: Expression
@@ -133,7 +161,6 @@ final class AndExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 }
 
-
 class EqualityExpression: Expression, InfixOperator, CustomStringConvertible {
   let lhs: Expression
   let rhs: Expression
@@ -169,7 +196,6 @@ class EqualityExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 }
 
-
 class NumericExpression: Expression, InfixOperator, CustomStringConvertible {
   let lhs: Expression
   let rhs: Expression
@@ -180,7 +206,7 @@ class NumericExpression: Expression, InfixOperator, CustomStringConvertible {
   }
 
   var description: String {
-    return "(\(lhs) \(op) \(rhs))"
+    return "(\(lhs) \(symbol) \(rhs))"
   }
 
   func evaluate(context: Context) throws -> Bool {
@@ -198,60 +224,55 @@ class NumericExpression: Expression, InfixOperator, CustomStringConvertible {
     return false
   }
 
-  var op: String {
+  var symbol: String {
     return ""
   }
 
-  func compare(lhs: Float80, rhs: Float80) -> Bool {
+  func compare(lhs: Number, rhs: Number) -> Bool {
     return false
   }
 }
 
-
 class MoreThanExpression: NumericExpression {
-  override var op: String {
+  override var symbol: String {
     return ">"
   }
 
-  override func compare(lhs: Float80, rhs: Float80) -> Bool {
+  override func compare(lhs: Number, rhs: Number) -> Bool {
     return lhs > rhs
   }
 }
 
-
 class MoreThanEqualExpression: NumericExpression {
-  override var op: String {
+  override var symbol: String {
     return ">="
   }
 
-  override func compare(lhs: Float80, rhs: Float80) -> Bool {
+  override func compare(lhs: Number, rhs: Number) -> Bool {
     return lhs >= rhs
   }
 }
 
-
 class LessThanExpression: NumericExpression {
-  override var op: String {
+  override var symbol: String {
     return "<"
   }
 
-  override func compare(lhs: Float80, rhs: Float80) -> Bool {
+  override func compare(lhs: Number, rhs: Number) -> Bool {
     return lhs < rhs
   }
 }
 
-
 class LessThanEqualExpression: NumericExpression {
-  override var op: String {
+  override var symbol: String {
     return "<="
   }
 
-  override func compare(lhs: Float80, rhs: Float80) -> Bool {
+  override func compare(lhs: Number, rhs: Number) -> Bool {
     return lhs <= rhs
   }
 }
 
-
 class InequalityExpression: EqualityExpression {
   override var description: String {
     return "(\(lhs) != \(rhs))"
@@ -262,38 +283,38 @@ class InequalityExpression: EqualityExpression {
   }
 }
 
-
-func toNumber(value: Any) -> Float80? {
+// swiftlint:disable:next cyclomatic_complexity
+func toNumber(value: Any) -> Number? {
     if let value = value as? Float {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? Double {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? UInt {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? Int {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? Int8 {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? Int16 {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? Int32 {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? Int64 {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? UInt8 {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? UInt16 {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? UInt32 {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? UInt64 {
-        return Float80(value)
-    } else if let value = value as? Float80 {
+        return Number(value)
+    } else if let value = value as? Number {
         return value
     } else if let value = value as? Float64 {
-        return Float80(value)
+        return Number(value)
     } else if let value = value as? Float32 {
-        return Float80(value)
+        return Number(value)
     }
 
     return nil

Sources/Extension.swift

@@ -1,67 +1,32 @@
-protocol FilterType {
-  func invoke(value: Any?, arguments: [Any?]) throws -> Any?
-}
-
-enum Filter: FilterType {
-  case simple(((Any?) throws -> Any?))
-  case arguments(((Any?, [Any?]) throws -> Any?))
-
-  func invoke(value: Any?, arguments: [Any?]) throws -> Any? {
-    switch self {
-    case let .simple(filter):
-      if !arguments.isEmpty {
-        throw TemplateSyntaxError("cannot invoke filter with an argument")
-      }
-
-      return try filter(value)
-    case let .arguments(filter):
-      return try filter(value, arguments)
-    }
-  }
-}
-
-
-public class Namespace {
-  public typealias TagParser = (TokenParser, Token) throws -> NodeType
-
+open class Extension {
+  typealias TagParser = (TokenParser, Token) throws -> NodeType
   var tags = [String: TagParser]()
+
   var filters = [String: Filter]()
 
   public init() {
-    registerDefaultTags()
-    registerDefaultFilters()
-  }
-
-  fileprivate func registerDefaultTags() {
-    registerTag("for", parser: ForNode.parse)
-    registerTag("if", parser: IfNode.parse)
-    registerTag("ifnot", parser: IfNode.parse_ifnot)
-#if !os(Linux)
-    registerTag("now", parser: NowNode.parse)
-#endif
-    registerTag("include", parser: IncludeNode.parse)
-    registerTag("extends", parser: ExtendsNode.parse)
-    registerTag("block", parser: BlockNode.parse)
-  }
-
-  fileprivate func registerDefaultFilters() {
-    registerFilter("default", filter: defaultFilter)
-    registerFilter("capitalize", filter: capitalise)
-    registerFilter("uppercase", filter: uppercase)
-    registerFilter("lowercase", filter: lowercase)
-    registerFilter("join", filter: joinFilter)
   }
 
   /// Registers a new template tag
-  public func registerTag(_ name: String, parser: @escaping TagParser) {
+  public func registerTag(_ name: String, parser: @escaping (TokenParser, Token) throws -> NodeType) {
     tags[name] = parser
   }
 
   /// 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
-      return SimpleNode(handler: handler)
-    })
+    registerTag(name) { _, token in
+      SimpleNode(token: token, handler: handler)
+    }
+  }
+
+  /// Registers boolean filter with it's negative counterpart
+  // swiftlint:disable:next discouraged_optional_boolean
+  public func registerFilter(name: String, negativeFilterName: String, filter: @escaping (Any?) throws -> Bool?) {
+    filters[name] = .simple(filter)
+    filters[negativeFilterName] = .simple {
+      guard let result = try filter($0) else { return nil }
+      return !result
+    }
   }
 
   /// Registers a template filter with the given name
@@ -71,6 +36,64 @@ public class Namespace {
 
   /// 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()
+    registerDefaultTags()
+    registerDefaultFilters()
+  }
+
+  fileprivate func registerDefaultTags() {
+    registerTag("for", parser: ForNode.parse)
+    registerTag("if", parser: IfNode.parse)
+    registerTag("ifnot", parser: IfNode.parse_ifnot)
+    #if !os(Linux)
+      registerTag("now", parser: NowNode.parse)
+    #endif
+    registerTag("include", parser: IncludeNode.parse)
+    registerTag("extends", parser: ExtendsNode.parse)
+    registerTag("block", parser: BlockNode.parse)
+    registerTag("filter", parser: FilterNode.parse)
+  }
+
+  fileprivate func registerDefaultFilters() {
+    registerFilter("default", filter: defaultFilter)
+    registerFilter("capitalize", filter: capitalise)
+    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?], context: Context) throws -> Any?
+}
+
+enum Filter: FilterType {
+  case simple(((Any?) throws -> Any?))
+  case arguments(((Any?, [Any?], Context) throws -> Any?))
+
+  func invoke(value: Any?, arguments: [Any?], context: Context) throws -> Any? {
+    switch self {
+    case let .simple(filter):
+      if !arguments.isEmpty {
+        throw TemplateSyntaxError("Can't invoke filter with an argument")
+      }
+      return try filter(value)
+    case let .arguments(filter):
+      return try filter(value, arguments, context)
+    }
+  }
+}

Sources/FilterTag.swift

@@ -0,0 +1,36 @@
+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
+
+    guard bits.count == 2 else {
+      throw TemplateSyntaxError("'filter' tag takes one argument, the filter expression")
+    }
+
+    let blocks = try parser.parse(until(["endfilter"]))
+
+    guard parser.nextToken() != nil else {
+      throw TemplateSyntaxError("`endfilter` was not found.")
+    }
+
+    let resolvable = try parser.compileFilter("filter_value|\(bits[1])", containedIn: token)
+    return FilterNode(nodes: blocks, resolvable: resolvable, token: token)
+  }
+
+  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]) {
+      try VariableNode(variable: resolvable, token: token).render(context)
+    }
+  }
+}

Sources/Filters.swift

@@ -1,39 +1,30 @@
-func toString(_ value: Any?) -> String? {
-  if let value = value as? String {
-    return value
-  } else if let value = value as? CustomStringConvertible {
-    return value.description
-  }
-
-  return nil
-}
-
 func capitalise(_ value: Any?) -> Any? {
-  if let value = toString(value) {
-    return value.capitalized
+  if let array = value as? [Any?] {
+    return array.map { stringify($0).capitalized }
+  } else {
+    return stringify(value).capitalized
   }
-
-  return value
 }
 
 func uppercase(_ value: Any?) -> Any? {
-  if let value = toString(value) {
-    return value.uppercased()
+  if let array = value as? [Any?] {
+    return array.map { stringify($0).uppercased() }
+  } else {
+    return stringify(value).uppercased()
   }
-
-  return value
 }
 
 func lowercase(_ value: Any?) -> Any? {
-  if let value = toString(value) {
-    return value.lowercased()
+  if let array = value as? [Any?] {
+    return array.map { stringify($0).lowercased() }
+  } else {
+    return stringify(value).lowercased()
   }
-
-  return value
 }
 
 func defaultFilter(value: Any?, arguments: [Any?]) -> Any? {
-  if let value = value {
+  // value can be optional wrapping nil, so this way we check for underlying value
+  if let value = value, String(describing: value) != "nil" {
     return value
   }
 
@@ -47,17 +38,92 @@ func defaultFilter(value: Any?, arguments: [Any?]) -> Any? {
 }
 
 func joinFilter(value: Any?, arguments: [Any?]) throws -> Any? {
-  guard arguments.count == 1 else {
-    throw TemplateSyntaxError("'join' filter takes a single argument")
+  guard arguments.count < 2 else {
+    throw TemplateSyntaxError("'join' filter takes at most one argument")
   }
 
-  guard let separator = arguments.first as? String else {
-    throw TemplateSyntaxError("'join' filter takes a separator as string")
+  let separator = stringify(arguments.first ?? "")
+
+  if let value = value as? [Any] {
+    return value
+      .map(stringify)
+      .joined(separator: separator)
   }
 
-  if let value = value as? [String] {
-    return value.joined(separator: separator)
-  }
-
-  return nil
+  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/ForTag.swift

@@ -1,20 +1,38 @@
-class ForNode : NodeType {
+import Foundation
+
+class ForNode: NodeType {
   let resolvable: Resolvable
-  let loopVariable:String
-  let nodes:[NodeType]
+  let loopVariables: [String]
+  let nodes: [NodeType]
   let emptyNodes: [NodeType]
+  let `where`: Expression?
+  let token: Token?
 
-  class func parse(_ parser:TokenParser, token:Token) throws -> NodeType {
-    let components = token.components()
+  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
+    let components = token.components
 
-    guard components.count == 4 && components[2] == "in" else {
-      throw TemplateSyntaxError("'for' statements should use the following 'for x in y' `\(token.contents)`.")
+    func hasToken(_ token: String, at index: Int) -> Bool {
+      return components.count > (index + 1) && components[index] == token
     }
 
-    let loopVariable = components[1]
-    let variable = components[3]
+    func endsOrHasToken(_ token: String, at index: Int) -> Bool {
+      return components.count == index || hasToken(token, at: index)
+    }
 
-    var emptyNodes = [NodeType]()
+    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"]))
 
@@ -22,42 +40,137 @@ class ForNode : NodeType {
       throw TemplateSyntaxError("`endfor` was not found.")
     }
 
+    var emptyNodes = [NodeType]()
     if token.contents == "empty" {
       emptyNodes = try parser.parse(until(["endfor"]))
       _ = parser.nextToken()
     }
 
-    let filter = try parser.compileFilter(variable)
-    return ForNode(resolvable: filter, loopVariable: loopVariable, nodes: forNodes, emptyNodes:emptyNodes)
+    return ForNode(
+      resolvable: resolvable,
+      loopVariables: loopVariables,
+      nodes: forNodes,
+      emptyNodes: emptyNodes,
+      where: `where`,
+      token: token
+    )
   }
 
-  init(resolvable: Resolvable, loopVariable:String, nodes:[NodeType], emptyNodes:[NodeType]) {
+  init(
+    resolvable: Resolvable,
+    loopVariables: [String],
+    nodes: [NodeType],
+    emptyNodes: [NodeType],
+    where: Expression? = nil,
+    token: Token? = nil
+  ) {
     self.resolvable = resolvable
-    self.loopVariable = loopVariable
+    self.loopVariables = loopVariables
     self.nodes = nodes
     self.emptyNodes = emptyNodes
+    self.where = `where`
+    self.token = token
   }
 
   func render(_ context: Context) throws -> String {
-    let values = try resolvable.resolve(context)
+    var values = try resolve(context)
 
-    if let values = values as? [Any] , values.count > 0 {
-      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,
-        ]
-
-        return try context.push(dictionary: [loopVariable: item, "forloop": forContext]) {
-          try renderNodes(nodes, context)
+    if let `where` = self.where {
+      values = try values.filter { item -> Bool in
+        try push(value: item, context: context) {
+          try `where`.evaluate(context: context)
         }
-      }.joined(separator: "")
+      }
+    }
+
+    if !values.isEmpty {
+      let count = values.count
+
+      return try zip(0..., values)
+        .map { index, item in
+          let forContext: [String: Any] = [
+            "first": index == 0,
+            "last": index == (count - 1),
+            "counter": index + 1,
+            "counter0": index,
+            "length": count
+          ]
+
+          return try context.push(dictionary: ["forloop": forContext]) {
+            try push(value: item, context: context) {
+              try renderNodes(nodes, context)
+            }
+          }
+        }
+        .joined()
     }
 
     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
+  }
 }

Sources/IfTag.swift

@@ -12,8 +12,8 @@ enum Operator {
   }
 }
 
-
 let operators: [Operator] = [
+  .infix("in", 5, InExpression.self),
   .infix("or", 6, OrExpression.self),
   .infix("and", 7, AndExpression.self),
   .prefix("not", 8, NotExpression.self),
@@ -22,25 +22,22 @@ let operators: [Operator] = [
   .infix(">", 10, MoreThanExpression.self),
   .infix(">=", 10, MoreThanEqualExpression.self),
   .infix("<", 10, LessThanExpression.self),
-  .infix("<=", 10, LessThanEqualExpression.self),
+  .infix("<=", 10, LessThanEqualExpression.self)
 ]
 
-
 func findOperator(name: String) -> Operator? {
-  for op in operators {
-    if op.name == name {
-      return op
-    }
+  for `operator` in operators where `operator`.name == name {
+    return `operator`
   }
 
   return nil
 }
 
-
-enum IfToken {
-  case infix(name: String, bindingPower: Int, op: InfixOperator.Type)
-  case prefix(name: String, bindingPower: Int, op: PrefixOperator.Type)
-  case variable(Variable)
+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 {
@@ -49,10 +46,12 @@ enum IfToken {
       return bindingPower
     case .prefix(_, let bindingPower, _):
       return bindingPower
-    case .variable(_):
+    case .variable:
+      return 0
+    case .subExpression:
       return 0
     case .end:
-        return 0
+      return 0
     }
   }
 
@@ -60,11 +59,13 @@ enum IfToken {
     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):
+    case .prefix(_, let bindingPower, let operatorType):
       let expression = try parser.expression(bindingPower: bindingPower)
-      return op.init(expression: expression)
+      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")
     }
@@ -72,13 +73,15 @@ enum IfToken {
 
   func leftDenotation(left: Expression, parser: IfExpressionParser) throws -> Expression {
     switch self {
-    case .infix(_, let bindingPower, let op):
+    case .infix(_, let bindingPower, let operatorType):
       let right = try parser.expression(bindingPower: bindingPower)
-      return op.init(lhs: left, rhs: right)
+      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")
     }
@@ -94,26 +97,78 @@ enum IfToken {
   }
 }
 
-
 final class IfExpressionParser {
   let tokens: [IfToken]
   var position: Int = 0
 
-  init(components: [String]) {
-    self.tokens = 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)
-        }
-      }
+  private init(tokens: [IfToken]) {
+    self.tokens = tokens
+  }
 
-      return .variable(Variable(component))
+  static func parser(components: [String], environment: Environment, token: Token) throws -> IfExpressionParser {
+    return 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 IfExpressionParser.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 {
+      if $0 == "(" {
+          bracketsBalance += 1
+      } else if $0 == ")" {
+          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]
@@ -153,48 +208,71 @@ final class IfExpressionParser {
   }
 }
 
+/// Represents an if condition and the associated nodes when the condition
+/// evaluates
+final class IfCondition {
+  let expression: Expression?
+  let nodes: [NodeType]
 
-func parseExpression(components: [String]) throws -> Expression {
-  let parser = IfExpressionParser(components: components)
-  return try parser.parse()
+  init(expression: Expression?, nodes: [NodeType]) {
+    self.expression = expression
+    self.nodes = nodes
+  }
+
+  func render(_ context: Context) throws -> String {
+    return try context.push {
+      try renderNodes(nodes, context)
+    }
+  }
 }
 
-
-class IfNode : NodeType {
-  let expression: Expression
-  let trueNodes: [NodeType]
-  let falseNodes: [NodeType]
+class IfNode: NodeType {
+  let conditions: [IfCondition]
+  let token: Token?
 
   class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
-    var components = token.components()
+    var components = token.components
     components.removeFirst()
-    var trueNodes = [NodeType]()
-    var falseNodes = [NodeType]()
 
-    trueNodes = try parser.parse(until(["endif", "else"]))
+    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)
+    ]
 
-    guard let token = parser.nextToken() else {
+    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.")
     }
 
-    if token.contents == "else" {
-      falseNodes = try parser.parse(until(["endif"]))
-      _ = parser.nextToken()
-    }
-
-    let expression = try parseExpression(components: components)
-    return IfNode(expression: expression, trueNodes: trueNodes, falseNodes: falseNodes)
+    return IfNode(conditions: conditions, token: token)
   }
 
   class func parse_ifnot(_ parser: TokenParser, token: Token) throws -> NodeType {
-    var components = token.components()
+    var components = token.components
     guard components.count == 2 else {
-      throw TemplateSyntaxError("'ifnot' statements should use the following 'ifnot condition' `\(token.contents)`.")
+      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 {
@@ -206,25 +284,30 @@ class IfNode : NodeType {
       _ = parser.nextToken()
     }
 
-    let expression = try parseExpression(components: components)
-    return IfNode(expression: expression, trueNodes: trueNodes, falseNodes: falseNodes)
+    return IfNode(conditions: [
+      IfCondition(expression: expression, nodes: trueNodes),
+      IfCondition(expression: nil, nodes: falseNodes)
+    ], token: token)
   }
 
-  init(expression: Expression, trueNodes: [NodeType], falseNodes: [NodeType]) {
-    self.expression = expression
-    self.trueNodes = trueNodes
-    self.falseNodes = falseNodes
+  init(conditions: [IfCondition], token: Token? = nil) {
+    self.conditions = conditions
+    self.token = token
   }
 
   func render(_ context: Context) throws -> String {
-    let truthy = try expression.evaluate(context: context)
+    for condition in conditions {
+      if let expression = condition.expression {
+        let truthy = try expression.evaluate(context: context)
 
-    return try context.push {
-      if truthy {
-        return try renderNodes(trueNodes, context)
+        if truthy {
+          return try condition.render(context)
+        }
       } else {
-        return try renderNodes(falseNodes, context)
+        return try condition.render(context)
       }
     }
+
+    return ""
   }
 }

Sources/Include.swift

@@ -1,37 +1,48 @@
 import PathKit
 
-
-class IncludeNode : NodeType {
+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()
+    let bits = token.components
 
-    guard bits.count == 2 else {
-      throw TemplateSyntaxError("'include' tag takes one argument, the template file to be included")
+    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]))
+    return IncludeNode(templateName: Variable(bits[1]), includeContext: bits.count == 3 ? bits[2] : nil, token: token)
   }
 
-  init(templateName: Variable) {
+  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 loader = context["loader"] as? Loader else {
-      throw TemplateSyntaxError("Template loader not in context")
-    }
-
     guard let templateName = try self.templateName.resolve(context) as? String else {
       throw TemplateSyntaxError("'\(self.templateName)' could not be resolved as a string")
     }
 
-    guard let template = try loader.loadTemplate(name: templateName) else {
-      throw TemplateSyntaxError("'\(templateName)' template not found")
-    }
+    let template = try context.environment.loadTemplate(name: templateName)
 
-    return try template.render(context)
+    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/Inheritence.swift

@@ -1,18 +1,38 @@
 class BlockContext {
   class var contextKey: String { return "block_context" }
 
-  var blocks: [String: BlockNode]
+  // 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
+    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? {
-    return blocks.removeValue(forKey: blockName)
+    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 {
@@ -25,13 +45,13 @@ extension Collection {
   }
 }
 
-
-class ExtendsNode : NodeType {
+class ExtendsNode: NodeType {
   let templateName: Variable
-  let blocks: [String:BlockNode]
+  let blocks: [String: BlockNode]
+  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("'extends' takes one argument, the template file to be extended")
@@ -42,61 +62,63 @@ class ExtendsNode : NodeType {
       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
+    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)
+    return ExtendsNode(templateName: Variable(bits[1]), blocks: nodes, token: token)
   }
 
-  init(templateName: Variable, blocks: [String: BlockNode]) {
+  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 loader = context["loader"] as? Loader else {
-      throw TemplateSyntaxError("Template loader not in context")
-    }
-
     guard let templateName = try self.templateName.resolve(context) as? String else {
       throw TemplateSyntaxError("'\(self.templateName)' could not be resolved as a string")
     }
 
-    guard let template = try loader.loadTemplate(name: templateName) else {
-      throw TemplateSyntaxError("'\(templateName)' template not found")
-    }
+    let baseTemplate = 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
-        }
+    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)
     }
 
-    return try context.push(dictionary: [BlockContext.contextKey: blockContext]) {
-      return try template.render(context)
+    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 {
+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()
+    let bits = token.components
 
     guard bits.count == 2 else {
       throw TemplateSyntaxError("'block' tag takes one argument, the block name")
@@ -105,19 +127,59 @@ class BlockNode : NodeType {
     let blockName = bits[1]
     let nodes = try parser.parse(until(["endblock"]))
     _ = parser.nextToken()
-    return BlockNode(name:blockName, nodes:nodes)
+    return BlockNode(name: blockName, nodes: nodes, token: token)
   }
 
-  init(name: String, nodes: [NodeType]) {
+  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 node = blockContext.pop(name) {
-      return try node.render(context)
+    if let blockContext = context[BlockContext.contextKey] as? BlockContext, let child = blockContext.pop(name) {
+      let childContext = try self.childContext(child, blockContext: blockContext, context: context)
+      // render extension node
+      do {
+        return try context.push(dictionary: childContext) {
+          try child.render(context)
+        }
+      } catch {
+        throw error.withToken(child.token)
+      }
     }
 
     return try renderNodes(nodes, context)
   }
+
+  // child node is a block node from child template that extends this node (has the same name)
+  func childContext(_ child: BlockNode, blockContext: BlockContext, context: Context) throws -> [String: Any] {
+    var childContext: [String: Any] = [BlockContext.contextKey: blockContext]
+
+    if let blockSuperNode = child.nodes.first(where: {
+      if let token = $0.token, case .variable = token.kind, token.contents == "block.super" {
+        return true
+      } else {
+        return false
+      }
+    }) {
+      do {
+        // render base node so that its content can be used as part of child node that extends it
+        childContext["block"] = ["super": try self.render(context)]
+      } catch {
+        if let error = error as? TemplateSyntaxError {
+          throw TemplateSyntaxError(
+            reason: error.reason,
+            token: blockSuperNode.token,
+            stackTrace: error.allTokens)
+        } else {
+          throw TemplateSyntaxError(
+            reason: "\(error)",
+            token: blockSuperNode.token,
+            stackTrace: [])
+        }
+      }
+    }
+    return childContext
+  }
 }

Sources/KeyPath.swift

@@ -0,0 +1,112 @@
+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/Lexer.swift

@@ -1,122 +1,198 @@
+import Foundation
+
+typealias Line = (content: String, number: UInt, range: Range<String.Index>)
+
 struct Lexer {
+  let templateName: String?
   let templateString: String
+  let lines: [Line]
 
-  init(templateString: String) {
+  /// The potential token start characters. In a template these appear after a
+  /// `{` character, for example `{{`, `{%`, `{#`, ...
+  private static let tokenChars: [Unicode.Scalar] = ["{", "%", "#"]
+
+  /// 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] = [
+    "{": "}",
+    "%": "%",
+    "#": "#"
+  ]
+
+  init(templateName: String? = nil, templateString: String) {
+    self.templateName = templateName
     self.templateString = templateString
+
+    self.lines = templateString.components(separatedBy: .newlines).enumerated().compactMap {
+      guard !$0.element.isEmpty,
+        let range = templateString.range(of: $0.element) else { return nil }
+      return (content: $0.element, number: UInt($0.offset + 1), range)
+    }
   }
 
-  func createToken(string:String) -> Token {
+  /// 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() -> String {
-      let start = string.index(string.startIndex, offsetBy: 2)
-      let end = string.index(string.endIndex, offsetBy: -2)
-      return string[start..<end].trim(character: " ")
+      guard string.count > 4 else { return "" }
+      let trimmed = String(string.dropFirst(2).dropLast(2))
+        .components(separatedBy: "\n")
+        .filter { !$0.isEmpty }
+        .map { $0.trim(character: " ") }
+        .joined(separator: " ")
+      return trimmed
     }
 
-    if string.hasPrefix("{{") {
-      return .variable(value: strip())
-    } else if string.hasPrefix("{%") {
-      return .block(value: strip())
-    } else if string.hasPrefix("{#") {
-      return .comment(value: strip())
+    if string.hasPrefix("{{") || string.hasPrefix("{%") || string.hasPrefix("{#") {
+      let value = strip()
+      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: value, at: sourceMap)
+      } else if string.hasPrefix("{#") {
+        return .comment(value: value, at: sourceMap)
+      }
     }
 
-    return .text(value: string)
+    let location = rangeLocation(range)
+    let sourceMap = SourceMap(filename: templateName, location: location)
+    return .text(value: string, at: sourceMap)
   }
 
-  /// Returns an array of tokens from a given template string.
+  /// 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)
-
-    let map = [
-      "{{": "}}",
-      "{%": "%}",
-      "{#": "#}",
-    ]
-
     while !scanner.isEmpty {
-      if let text = scanner.scan(until: ["{{", "{%", "{#"]) {
-        if !text.1.isEmpty {
-          tokens.append(createToken(string: text.1))
+      if let (char, text) = scanner.scanForTokenStart(Lexer.tokenChars) {
+        if !text.isEmpty {
+          tokens.append(createToken(string: text, at: scanner.range))
         }
 
-        let end = map[text.0]!
-        let result = scanner.scan(until: end, returnUntil: true)
-        tokens.append(createToken(string: result))
+        guard let end = Lexer.tokenCharMap[char] else { continue }
+        let result = scanner.scanForTokenEnd(end)
+        tokens.append(createToken(string: result, at: scanner.range))
       } else {
-        tokens.append(createToken(string: scanner.content))
+        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 {
     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
-        }
+  /// 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 content.unicodeScalars.enumerated() {
+      if foundChar && char == Scanner.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)
       }
-
-      index = content.index(after: index)
     }
 
+    content = ""
     return ""
   }
 
-  func scan(until: [String]) -> (String, String)? {
-    if until.isEmpty {
-      return nil
-    }
+  /// 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
 
-    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)
-        }
+    range = range.upperBound..<range.upperBound
+    for (index, char) in content.unicodeScalars.enumerated() {
+      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 == Scanner.tokenStartDelimiter)
       }
-
-      index = content.index(after: index)
     }
 
     return nil
   }
 }
 
-
 extension String {
   func findFirstNot(character: Character) -> String.Index? {
     var index = startIndex
@@ -147,6 +223,8 @@ extension String {
   func trim(character: Character) -> String {
     let first = findFirstNot(character: character) ?? startIndex
     let last = findLastNot(character: character) ?? endIndex
-    return self[first..<last]
+    return String(self[first..<last])
   }
 }
+
+public typealias ContentLocation = (content: String, lineNumber: UInt, lineOffset: Int)

Sources/Loader.swift

@@ -0,0 +1,124 @@
+import Foundation
+import PathKit
+
+public protocol Loader {
+  func loadTemplate(name: String, environment: Environment) throws -> Template
+  func loadTemplate(names: [String], environment: Environment) throws -> Template
+}
+
+extension Loader {
+  public func loadTemplate(names: [String], environment: Environment) throws -> Template {
+    for name in names {
+      do {
+        return try loadTemplate(name: name, environment: environment)
+      } catch is TemplateDoesNotExist {
+        continue
+      } catch {
+        throw error
+      }
+    }
+
+    throw TemplateDoesNotExist(templateNames: names, loader: self)
+  }
+}
+
+// A class for loading a template from disk
+public class FileSystemLoader: Loader, CustomStringConvertible {
+  public let paths: [Path]
+
+  public init(paths: [Path]) {
+    self.paths = paths
+  }
+
+  public init(bundle: [Bundle]) {
+    self.paths = bundle.map {
+      Path($0.bundlePath)
+    }
+  }
+
+  public var description: String {
+    return "FileSystemLoader(\(paths))"
+  }
+
+  public func loadTemplate(name: String, environment: Environment) throws -> Template {
+    for path in paths {
+      let templatePath = try path.safeJoin(path: Path(name))
+
+      if !templatePath.exists {
+        continue
+      }
+
+      let content: String = try templatePath.read()
+      return environment.templateClass.init(templateString: content, environment: environment, name: name)
+    }
+
+    throw TemplateDoesNotExist(templateNames: [name], loader: self)
+  }
+
+  public func loadTemplate(names: [String], environment: Environment) throws -> Template {
+    for path in paths {
+      for templateName in names {
+        let templatePath = try path.safeJoin(path: Path(templateName))
+
+        if templatePath.exists {
+          let content: String = try templatePath.read()
+          return environment.templateClass.init(templateString: content, environment: environment, name: templateName)
+        }
+      }
+    }
+
+    throw TemplateDoesNotExist(templateNames: names, loader: self)
+  }
+}
+
+public class DictionaryLoader: Loader {
+  public let templates: [String: String]
+
+  public init(templates: [String: String]) {
+    self.templates = templates
+  }
+
+  public func loadTemplate(name: String, environment: Environment) throws -> Template {
+    if let content = templates[name] {
+      return environment.templateClass.init(templateString: content, environment: environment, name: name)
+    }
+
+    throw TemplateDoesNotExist(templateNames: [name], loader: self)
+  }
+
+  public func loadTemplate(names: [String], environment: Environment) throws -> Template {
+    for name in names {
+      if let content = templates[name] {
+        return environment.templateClass.init(templateString: content, environment: environment, name: name)
+      }
+    }
+
+    throw TemplateDoesNotExist(templateNames: names, loader: self)
+  }
+}
+
+extension Path {
+  func safeJoin(path: Path) throws -> Path {
+    let newPath = self + path
+
+    if !newPath.absolute().description.hasPrefix(absolute().description) {
+      throw SuspiciousFileOperation(basePath: self, path: newPath)
+    }
+
+    return newPath
+  }
+}
+
+class SuspiciousFileOperation: Error {
+  let basePath: Path
+  let path: Path
+
+  init(basePath: Path, path: Path) {
+    self.basePath = basePath
+    self.path = path
+  }
+
+  var description: String {
+    return "Path `\(path)` is located outside of base path `\(basePath)`"
+  }
+}

Sources/Node.swift

@@ -1,35 +1,32 @@
 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
-}
+  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 {
-  return try nodes.map { try $0.render(context) }.joined(separator: "")
+public func renderNodes(_ nodes: [NodeType], _ context: Context) throws -> String {
+  return try nodes
+    .map {
+      do {
+        return try $0.render(context)
+      } catch {
+        throw error.withToken($0.token)
+      }
+    }
+    .joined()
 }
 
-public class SimpleNode : NodeType {
-  public let handler:(Context) throws -> String
+public class SimpleNode: NodeType {
+  public let handler: (Context) throws -> String
+  public let token: Token?
 
-  public init(handler: @escaping (Context) throws -> String) {
+  public init(token: Token, handler: @escaping (Context) throws -> String) {
+    self.token = token
     self.handler = handler
   }
 
@@ -38,47 +35,115 @@ public class SimpleNode : NodeType {
   }
 }
 
+public class TextNode: NodeType {
+  public let text: String
+  public let token: Token?
 
-public class TextNode : NodeType {
-  public let text:String
-
-  public init(text:String) {
+  public init(text: String) {
     self.text = text
+    self.token = nil
   }
 
-  public func render(_ context:Context) throws -> String {
+  public func render(_ context: Context) throws -> String {
     return self.text
   }
 }
 
-
 public protocol Resolvable {
   func resolve(_ context: Context) throws -> Any?
 }
 
-
-public class VariableNode : NodeType {
+public class VariableNode: NodeType {
   public let variable: Resolvable
+  public var token: Token?
+  let condition: Expression?
+  let elseExpression: Resolvable?
 
-  public init(variable: Resolvable) {
-    self.variable = variable
+  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
+    let components = token.components
+
+    func hasToken(_ token: String, at index: Int) -> Bool {
+      return components.count > (index + 1) && components[index] == token
+    }
+
+    let condition: Expression?
+    let elseExpression: Resolvable?
+
+    if hasToken("if", at: 1) {
+      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 = components.suffix(from: elseIndex.advanced(by: 1)).joined(separator: " ")
+        elseExpression = try parser.compileResolvable(elseToken, containedIn: token)
+      } else {
+        condition = try parser.compileExpression(components: Array(components), token: token)
+        elseExpression = nil
+      }
+    } else {
+      condition = nil
+      elseExpression = nil
+    }
+
+    guard let resolvable = components.first else {
+      throw TemplateSyntaxError(reason: "Missing variable name", token: token)
+    }
+    let filter = try parser.compileResolvable(resolvable, containedIn: token)
+    return VariableNode(variable: filter, token: token, condition: condition, elseExpression: elseExpression)
   }
 
-  public init(variable: String) {
+  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 {
-    let result = try variable.resolve(context)
-
-    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
+    if let condition = self.condition, try condition.evaluate(context: context) == false {
+      return try elseExpression?.resolve(context).map(stringify) ?? ""
     }
 
-    return ""
+    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] {
+  return 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/NowTag.swift

@@ -1,43 +1,44 @@
 #if !os(Linux)
 import Foundation
 
+class NowNode: NodeType {
+  let format: Variable
+  let token: Token?
 
-class NowNode : NodeType {
-  let format:Variable
+  class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
+    var format: Variable?
 
-  class func parse(_ parser:TokenParser, token:Token) throws -> NodeType {
-    var format:Variable?
-
-    let components = token.components()
+    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/Parser.swift

@@ -1,10 +1,8 @@
 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
-        }
+    if let name = token.components.first {
+      for tag in tags where name == tag {
+        return true
       }
     }
 
@@ -12,17 +10,16 @@ public func until(_ tags: [String]) -> ((TokenParser, Token) -> Bool) {
   }
 }
 
-
 /// 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 namespace: Namespace
+  fileprivate let environment: Environment
 
-  public init(tokens: [Token], namespace: Namespace) {
+  public init(tokens: [Token], environment: Environment) {
     self.tokens = tokens
-    self.namespace = namespace
+    self.environment = environment
   }
 
   /// Parse the given tokens into nodes
@@ -30,30 +27,30 @@ public class TokenParser {
     return try parse(nil)
   }
 
-  public func parse(_ parse_until:((_ parser:TokenParser, _ token:Token) -> (Bool))?) throws -> [NodeType] {
+  public func parse(_ parseUntil: ((_ parser: TokenParser, _ token: Token) -> (Bool))?) throws -> [NodeType] {
     var nodes = [NodeType]()
 
-    while tokens.count > 0 {
-      let token = nextToken()!
+    while !tokens.isEmpty {
+      guard let token = nextToken() else { break }
 
-      switch token {
-      case .text(let text):
-        nodes.append(TextNode(text: text))
+      switch token.kind {
+      case .text:
+        nodes.append(TextNode(text: token.contents))
       case .variable:
-        nodes.append(VariableNode(variable: try compileFilter(token.contents)))
+        try nodes.append(VariableNode.parse(self, token: token))
       case .block:
-        let tag = token.components().first
-
-        if let parse_until = parse_until , parse_until(self, token) {
+        if let parseUntil = parseUntil, parseUntil(self, token) {
           prependToken(token)
           return nodes
         }
 
-        if let tag = tag {
-          if let parser = namespace.tags[tag] {
-            nodes.append(try parser(self, token))
-          } else {
-            throw TemplateSyntaxError("Unknown template tag '\(tag)'")
+        if let tag = token.components.first {
+          do {
+            let parser = try environment.findTag(name: tag)
+            let node = try parser(self, token)
+            nodes.append(node)
+          } catch {
+            throw error.withToken(token)
           }
         }
       case .comment:
@@ -65,26 +62,161 @@ public class TokenParser {
   }
 
   public func nextToken() -> Token? {
-    if tokens.count > 0 {
+    if !tokens.isEmpty {
       return tokens.remove(at: 0)
     }
 
     return nil
   }
 
-  public func prependToken(_ token:Token) {
+  public func prependToken(_ token: Token) {
     tokens.insert(token, at: 0)
   }
 
-  func findFilter(_ name: String) throws -> FilterType {
-    if let filter = namespace.filters[name] {
-      return filter
-    }
-
-    throw TemplateSyntaxError("Invalid filter '\(name)'")
+  /// Create filter expression from a string contained in provided token
+  public func compileFilter(_ filterToken: String, containedIn token: Token) throws -> Resolvable {
+    return try environment.compileFilter(filterToken, containedIn: token)
   }
 
-  public func compileFilter(_ token: String) throws -> Resolvable {
-    return try FilterExpression(token: token, parser: self)
+  /// Create boolean expression from components contained in provided token
+  public func compileExpression(components: [String], token: Token) throws -> Expression {
+    return 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 {
+    return try environment.compileResolvable(token, containedIn: containingToken)
+  }
+}
+
+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 {
+    return 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 {
+    return 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 {
+    return 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 {
+    return 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 {
+    return 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/Template.swift

@@ -6,55 +6,75 @@ let NSFileNoSuchFileError = 4
 #endif
 
 /// A class representing a template
-public class Template: ExpressibleByStringLiteral {
+open class Template: ExpressibleByStringLiteral {
+  let templateString: String
+  var environment: Environment
   let tokens: [Token]
 
+  /// The name of the loaded Template if the Template was loaded from a Loader
+  public let name: String?
+
   /// Create a template with a template string
-  public init(templateString: String) {
-    let lexer = Lexer(templateString: templateString)
+  public required init(templateString: String, environment: Environment? = nil, name: String? = nil) {
+    self.environment = environment ?? Environment()
+    self.name = name
+    self.templateString = templateString
+
+    let lexer = Lexer(templateName: name, templateString: templateString)
     tokens = lexer.tokenize()
   }
 
   /// Create a template with the given name inside the given bundle
-  public convenience init(named:String, inBundle bundle:Bundle? = nil) throws {
-    let useBundle = bundle ??  Bundle.main
+  @available(*, deprecated, message: "Use Environment/FileSystemLoader instead")
+  public convenience init(named: String, inBundle bundle: Bundle? = nil) throws {
+    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
-  public convenience init(URL:Foundation.URL) throws {
+  @available(*, deprecated, message: "Use Environment/FileSystemLoader instead")
+  public convenience init(URL: Foundation.URL) throws {
     try self.init(path: Path(URL.path))
   }
 
   /// Create a template with a file found at the given path
-  public convenience init(path: Path) throws {
-    self.init(templateString: try path.read())
+  @available(*, deprecated, message: "Use Environment/FileSystemLoader instead")
+  public convenience init(path: Path, environment: Environment? = nil, name: String? = nil) throws {
+    self.init(templateString: try path.read(), environment: environment, name: name)
   }
 
-  // Create a template with a template string literal
-  public convenience required init(stringLiteral value: String) {
+  // MARK: ExpressibleByStringLiteral
+
+  // Create a templaVte with a template string literal
+  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
-  public func render(_ context: Context? = nil) throws -> String {
-    let context = context ?? Context()
-    let parser = TokenParser(tokens: tokens, namespace: context.namespace)
+  /// Render the given template with a context
+  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))
+  }
 }

Sources/TemplateLoader.swift

@@ -1,65 +0,0 @@
-import Foundation
-import PathKit
-
-
-public protocol Loader {
-  func loadTemplate(name: String) throws -> Template?
-  func loadTemplate(names: [String]) throws -> Template?
-}
-
-
-extension Loader {
-  func loadTemplate(names: [String]) throws -> Template? {
-    for name in names {
-      let template = try loadTemplate(name: name)
-
-      if template != nil {
-        return template
-      }
-    }
-
-    return nil
-  }
-}
-
-
-// A class for loading a template from disk
-public class FileSystemLoader: Loader {
-  public let paths: [Path]
-
-  public init(paths: [Path]) {
-    self.paths = paths
-  }
-
-  public init(bundle: [Bundle]) {
-    self.paths = bundle.map {
-      return Path($0.bundlePath)
-    }
-  }
-
-  public func loadTemplate(name: String) throws -> Template? {
-    for path in paths {
-      let templatePath = path + Path(name)
-
-      if templatePath.exists {
-        return try Template(path: templatePath)
-      }
-    }
-
-    return nil
-  }
-
-  public func loadTemplate(names: [String]) throws -> Template? {
-    for path in paths {
-      for templateName in names {
-        let templatePath = path + Path(templateName)
-
-        if templatePath.exists {
-          return try Template(path: templatePath)
-        }
-      }
-    }
-
-    return nil
-  }
-}

Sources/Tokenizer.swift

@@ -1,21 +1,26 @@
 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
+      }
 
-    for character in self.characters {
       if character == separate {
         if separate != separator {
           word.append(separate)
-        }
-
-        if !word.isEmpty {
-          components.append(word)
+        } else if (singleQuoteCount % 2 == 0 || doubleQuoteCount % 2 == 0) && !word.isEmpty {
+          appendWord(word, to: &components)
           word = ""
         }
 
@@ -29,67 +34,97 @@ extension String {
     }
 
     if !word.isEmpty {
-      components.append(word)
+      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) {
+        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
 
-public enum Token : Equatable {
-  /// A token representing a piece of text.
-  case text(value: String)
+  init(filename: String? = nil, location: ContentLocation = ("", 0, 0)) {
+    self.filename = filename
+    self.location = location
+  }
 
-  /// A token representing a variable.
-  case variable(value: String)
+  static let unknown = SourceMap()
 
-  /// A token representing a comment.
-  case comment(value: String)
+  public static func == (lhs: SourceMap, rhs: SourceMap) -> Bool {
+    return lhs.filename == rhs.filename && lhs.location == rhs.location
+  }
+}
 
-  /// A token representing a template block.
-  case block(value: String)
+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
 
   /// 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 private(set) lazy var components: [String] = self.contents.smartSplit()
+
+  init(contents: String, kind: Kind, sourceMap: SourceMap) {
+    self.contents = contents
+    self.kind = kind
+    self.sourceMap = sourceMap
   }
 
-  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
+  /// A token representing a piece of text.
+  public static func text(value: String, at sourceMap: SourceMap) -> Token {
+    return Token(contents: value, kind: .text, sourceMap: sourceMap)
+  }
+
+  /// A token representing a variable.
+  public static func variable(value: String, at sourceMap: SourceMap) -> Token {
+    return Token(contents: value, kind: .variable, sourceMap: sourceMap)
+  }
+
+  /// A token representing a comment.
+  public static func comment(value: String, at sourceMap: SourceMap) -> Token {
+    return Token(contents: value, kind: .comment, sourceMap: sourceMap)
+  }
+
+  /// A token representing a template block.
+  public static func block(value: String, at sourceMap: SourceMap) -> Token {
+    return Token(contents: value, kind: .block, sourceMap: sourceMap)
+  }
+
+  public static func == (lhs: Token, rhs: Token) -> Bool {
+    return lhs.contents == rhs.contents && lhs.kind == rhs.kind && lhs.sourceMap == rhs.sourceMap
   }
 }

Sources/Variable.swift

@@ -1,15 +1,14 @@
 import Foundation
 
+typealias Number = Float
 
-class FilterExpression : Resolvable {
+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: " ") })
+  init(token: String, environment: Environment) throws {
+    let bits = token.smartSplit(separator: "|").map { String($0).trim(character: " ") }
     if bits.isEmpty {
-      filters = []
-      variable = Variable("")
       throw TemplateSyntaxError("Variable tags must include at least 1 argument")
     }
 
@@ -19,7 +18,7 @@ class FilterExpression : Resolvable {
     do {
       filters = try filterBits.map {
         let (name, arguments) = parseFilterComponents(token: $0)
-        let filter = try parser.findFilter(name)
+        let filter = try environment.findFilter(name)
         return (filter, arguments)
       }
     } catch {
@@ -31,15 +30,15 @@ class FilterExpression : Resolvable {
   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)
+    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 struct Variable: Equatable, Resolvable {
   public let variable: String
 
   /// Create a variable with a string representing the variable
@@ -47,66 +46,150 @@ public struct Variable : Equatable, Resolvable {
     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("\"")) {
+    if variable.count > 1 && ((variable.hasPrefix("'") && variable.hasSuffix("'")) || (variable.hasPrefix("\"") && variable.hasSuffix("\""))) {
       // String literal
-      return variable[variable.characters.index(after: variable.startIndex) ..< variable.characters.index(before: variable.endIndex)]
+      return String(variable[variable.index(after: variable.startIndex) ..< variable.index(before: variable.endIndex)])
     }
 
-    for bit in lookup() {
-      current = normalize(current)
+    // 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
+    }
 
-      if let context = current as? Context {
-        current = context[bit]
-      } else if let dictionary = current as? [String: Any] {
-        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)
+    var current: Any? = context
+    for bit in try lookup(context) {
+      current = resolve(bit: bit, context: current)
 
-        if current == nil {
-          return nil
-        }
-      } else {
+      if current == nil {
         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)
   }
+
+  // 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 object = context as? NSObject {  // NSKeyValueCoding
+      #if os(Linux)
+        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
+    }
+  }
 }
 
-public func ==(lhs: Variable, rhs: Variable) -> Bool {
-  return lhs.variable == rhs.variable
-}
+/// 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 {
@@ -120,19 +203,19 @@ protocol Normalizable {
   func normalize() -> Any?
 }
 
-extension Array : Normalizable {
+extension Array: Normalizable {
   func normalize() -> Any? {
     return map { $0 as Any }
   }
 }
 
-extension NSArray : Normalizable {
+extension NSArray: Normalizable {
   func normalize() -> Any? {
     return map { $0 as Any }
   }
 }
 
-extension Dictionary : Normalizable {
+extension Dictionary: Normalizable {
   func normalize() -> Any? {
     var dictionary: [String: Any] = [:]
 
@@ -150,10 +233,45 @@ extension Dictionary : Normalizable {
 
 func parseFilterComponents(token: String) -> (String, [Variable]) {
   var components = token.smartSplit(separator: ":")
-  let name = components.removeFirst()
+  let name = components.removeFirst().trim(character: " ")
   let variables = components
     .joined(separator: ":")
     .smartSplit(separator: ",")
-    .map { Variable($0) }
+    .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/_SwiftSupport.swift

@@ -0,0 +1,9 @@
+import Foundation
+
+#if !swift(>=4.2)
+extension ArraySlice where Element: Equatable {
+    func firstIndex(of element: Element) -> Int? {
+        return index(of: element)
+    }
+}
+#endif

Stencil.podspec.json

@@ -1,6 +1,6 @@
 {
   "name": "Stencil",
-  "version": "0.7.1",
+  "version": "0.14.2",
   "summary": "Stencil is a simple and powerful template language for Swift.",
   "homepage": "https://stencil.fuller.li",
   "license": {
@@ -12,8 +12,8 @@
   },
   "social_media_url": "https://twitter.com/kylefuller",
   "source": {
-    "git": "https://github.com/kylef/Stencil.git",
-    "tag": "0.7.1"
+    "git": "https://github.com/stencilproject/Stencil.git",
+    "tag": "0.14.2"
   },
   "source_files": [
     "Sources/*.swift"
@@ -23,8 +23,15 @@
     "osx": "10.9",
     "tvos": "9.0"
   },
+  "cocoapods_version": ">= 1.7.0",
+  "swift_versions": [
+    "4.2",
+    "5.0"
+  ],
   "requires_arc": true,
   "dependencies": {
-    "PathKit": [ "~> 0.7.0" ]
+    "PathKit": [
+      "~> 1.0.0"
+    ]
   }
 }

Tests/LinuxMain.swift

@@ -1,3 +1,8 @@
+import XCTest
+
 import StencilTests
 
-stencilTests()
+var tests = [XCTestCaseEntry]()
+tests += StencilTests.__allTests()
+
+XCTMain(tests)

Tests/StencilTests/.swiftlint.yml

@@ -0,0 +1,3 @@
+disabled_rules: # rule identifiers to exclude from running
+  - type_body_length
+  - file_length

Tests/StencilTests/ContextSpec.swift

@@ -1,80 +1,90 @@
 import Spectre
-import Stencil
+@testable import Stencil
+import XCTest
 
+final class ContextTests: XCTestCase {
+  func testContextSubscripting() {
+    describe("Context Subscripting") {
+      var context = Context()
+      $0.before {
+        context = Context(dictionary: ["name": "Kyle"])
+      }
 
-func testContext() {
-  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 {
+      $0.it("allows you to get a value via subscripting") {
         try expect(context["name"] as? String) == "Kyle"
       }
-    }
 
-    $0.it("allows you to override a parent's value") {
-      try context.push {
+      $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 pop to restore previous state") {
-      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 {
+      $0.it("allows you to remove a value via subscripting") {
         context["name"] = nil
+
         try expect(context["name"]).to.beNil()
       }
 
-      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"
+      $0.it("allows you to retrieve a value from a parent") {
+        try context.push {
+          try expect(context["name"] as? String) == "Kyle"
+        }
       }
 
-      try expect(didRun).to.beTrue()
-      try expect(context["name"] as? String) == "Kyle"
+      $0.it("allows you to override a parent's value") {
+        try context.push {
+          context["name"] = "Katie"
+          try expect(context["name"] as? String) == "Katie"
+        }
+      }
     }
+  }
 
-    $0.it("allows you to flatten the context contents") {
-      try context.push(dictionary: ["test": "abc"]) {
-        let flattened = context.flatten()
+  func testContextRestoration() {
+    describe("Context Restoration") {
+      var context = Context()
+      $0.before {
+        context = Context(dictionary: ["name": "Kyle"])
+      }
 
-        try expect(flattened.count) == 2
-        try expect(flattened["name"] as? String) == "Kyle"
-        try expect(flattened["test"] as? String) == "abc"
+      $0.it("allows you to pop to restore previous state") {
+        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"
+      }
+
+      $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()
+        try expect(context["name"] as? String) == "Kyle"
+      }
+
+      $0.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"
+        }
       }
     }
   }

Tests/StencilTests/EnvironmentSpec.swift

@@ -0,0 +1,448 @@
+import PathKit
+import Spectre
+@testable import Stencil
+import XCTest
+
+final class EnvironmentTests: XCTestCase {
+  var environment = Environment(loader: ExampleLoader())
+  var template: Template = ""
+
+  override func setUp() {
+    super.setUp()
+
+    let errorExtension = Extension()
+    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 = ""
+  }
+
+  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"
+    }
+
+    it("can load a template from a names") {
+      let template = try self.environment.loadTemplate(names: ["first.html", "example.html"])
+      try expect(template.name) == "example.html"
+    }
+  }
+
+  func testRendering() {
+    it("can render a template from a string") {
+      let result = try self.environment.renderTemplate(string: "Hello World")
+      try expect(result) == "Hello World"
+    }
+
+    it("can render a template from a file") {
+      let result = try self.environment.renderTemplate(name: "example.html")
+      try expect(result) == "Hello World!"
+    }
+
+    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() {
+    it("reports syntax error on invalid for tag syntax") {
+      self.template = "Hello {% for name in %}{{ name }}, {% endfor %}!"
+      try self.expectError(
+        reason: "'for' statements should use the syntax: `for <x> in <y> [where <condition>]`.",
+        token: "for name in"
+      )
+    }
+
+    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)
+  }
+}
+
+final class EnvironmentIncludeTemplateTests: XCTestCase {
+  var environment = Environment(loader: ExampleLoader())
+  var template: Template = ""
+  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 = ""
+  }
+
+  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)
+  }
+}
+
+final class EnvironmentBaseAndChildTemplateTests: XCTestCase {
+  var environment = Environment(loader: ExampleLoader())
+  var childTemplate: Template = ""
+  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 = ""
+  }
+
+  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: "block.super",
+                    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)
+  }
+}
+
+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: [])
+  }
+}
+
+private 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)
+  }
+}
+
+private class CustomTemplate: Template {
+  // swiftlint:disable discouraged_optional_collection
+  override func render(_ dictionary: [String: Any]? = nil) throws -> String {
+    return "here"
+  }
+}

Tests/StencilTests/ExpressionSpec.swift

@@ -1,282 +1,355 @@
 import Spectre
 @testable import Stencil
+import XCTest
 
+final class ExpressionsTests: XCTestCase {
+  let parser = TokenParser(tokens: [], environment: Environment())
 
-func testExpressions() {
-  describe("Expression") {
-    $0.describe("VariableExpression") {
-      let expression = VariableExpression(variable: Variable("value"))
-
-      $0.it("evaluates to true when value is not nil") {
-        let context = Context(dictionary: ["value": "known"])
-        try expect(try expression.evaluate(context: context)).to.beTrue()
-      }
-
-      $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"])
-        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"])
-        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"])
-
-        $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"])
-
-        $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"])
-
-        $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"])
-
-        $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"])
-
-        $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"])
-
-        $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"])
-
-        $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"])
-
-        $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"])
-
-        $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()
-        }
-      }
+  private func makeExpression(_ components: [String]) -> Expression {
+    do {
+      let parser = try IfExpressionParser.parser(
+        components: components,
+        environment: Environment(),
+        token: .text(value: "", at: .unknown)
+      )
+      return try parser.parse()
+    } catch {
+      fatalError(error.localizedDescription)
     }
   }
+
+  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: StaticExpression(value: true))
+      try expect(expression.evaluate(context: Context())).to.beFalse()
+    }
+
+    it("returns falsy for negative expressions") {
+      let expression = NotExpression(expression: StaticExpression(value: 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

@@ -1,16 +1,16 @@
 import Spectre
-import Stencil
+@testable import Stencil
+import XCTest
 
-
-func testFilter() {
-  describe("template filters") {
+final class FilterTests: XCTestCase {
+  func testRegistration() {
     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 namespace = Namespace()
-      namespace.registerFilter("repeat") { (value: Any?) in
+      let repeatExtension = Extension()
+      repeatExtension.registerFilter("repeat") { (value: Any?) in
         if let value = value as? String {
           return "\(value) \(value)"
         }
@@ -18,103 +18,436 @@ func testFilter() {
         return nil
       }
 
-      let result = try template.render(Context(dictionary: context, namespace: namespace))
+      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 arguments") {
-      let template = Template(templateString: "{{ name|repeat:'value' }}")
-
-      let namespace = Namespace()
-      namespace.registerFilter("repeat") { value, arguments in
-        if !arguments.isEmpty {
-          return "\(value!) \(value!) with args \(arguments.first!!)"
+    it("allows you to register boolean filters") {
+      let repeatExtension = Extension()
+      repeatExtension.registerFilter(name: "isPositive", negativeFilterName: "isNotPositive") { (value: Any?) in
+        if let value = value as? Int {
+          return value > 0
         }
-
         return nil
       }
 
-      let result = try template.render(Context(dictionary: context, namespace: namespace))
-      try expect(result) == "Kyle Kyle with args value"
+      let result = try Template(templateString: "{{ value|isPositive }}")
+        .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 which throws") {
+    it("allows you to register a custom which throws") {
       let template = Template(templateString: "{{ name|repeat }}")
-      let namespace = Namespace()
-      namespace.registerFilter("repeat") { (value: Any?) in
+      let repeatExtension = Extension()
+      repeatExtension.registerFilter("repeat") { (_: Any?) in
         throw TemplateSyntaxError("No Repeat")
       }
 
-      try expect(try template.render(Context(dictionary: context, namespace: namespace))).toThrow(TemplateSyntaxError("No Repeat"))
+      let context = Context(dictionary: context, environment: Environment(extensions: [repeatExtension]))
+      try expect(try template.render(context))
+        .toThrow(TemplateSyntaxError(reason: "No Repeat", token: template.tokens.first))
     }
 
-    $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") {
+    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 template = Template(templateString: "{{ name|capitalize }}")
+    let repeatExtension = Extension()
+    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"
     }
-  }
 
-
-  describe("uppercase filter") {
-    let template = Template(templateString: "{{ name|uppercase }}")
-
-    $0.it("transforms a string to be uppercase") {
+    it("transforms a string to be uppercase") {
+      let template = Template(templateString: "{{ name|uppercase }}")
       let result = try template.render(Context(dictionary: ["name": "kyle"]))
       try expect(result) == "KYLE"
     }
-  }
 
-  describe("lowercase filter") {
-    let template = Template(templateString: "{{ name|lowercase }}")
-
-    $0.it("transforms a string to be lowercase") {
+    it("transforms a string to be lowercase") {
+      let template = Template(templateString: "{{ name|lowercase }}")
       let result = try template.render(Context(dictionary: ["name": "Kyle"]))
       try expect(result) == "kyle"
     }
   }
 
-  describe("default filter") {
-    let template = Template(templateString: "Hello {{ name|default:\"World\" }}")
+  func testStringFiltersWithArrays() {
+    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") {
-      let template = Template(templateString: "Hello {{ name|default:a,b,c,\"World\" }}")
+    it("supports multiple defaults") {
+      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") {
-    let template = Template(templateString: "{{ value|join:\", \" }}")
+  func testJoinFilter() {
+    let template = Template(templateString: """
+      {{ value|join:", " }}
+      """)
 
-    $0.it("transforms a string to be lowercase") {
+    it("joins a collection of strings") {
       let result = try template.render(Context(dictionary: ["value": ["One", "Two"]]))
       try expect(result) == "One, Two"
     }
+
+    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"
+    }
+
+    it("can join by non string") {
+      let template = Template(templateString: """
+        {{ value|join:separator }}
+        """)
+      let result = try template.render(Context(dictionary: ["value": ["One", "Two"], "separator": true]))
+      try expect(result) == "OnetrueTwo"
+    }
+
+    it("can join without arguments") {
+      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
+      """
+    ]))
+    try expect(result) == """
+        One
+        Two
+      """
+  }
+
+  func testIndentNotEmptyLines() throws {
+    let template = Template(templateString: """
+      {{ value|indent }}
+      """)
+    let result = try template.render(Context(dictionary: [
+      "value": """
+      One
+
+
+      Two
+
+
+      """
+    ]))
+    try expect(result) == """
+      One
+
+
+          Two
+
+
+      """
+  }
+
+  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

@@ -0,0 +1,54 @@
+import Spectre
+import Stencil
+import XCTest
+
+final class FilterTagTests: XCTestCase {
+  func testFilterTag() {
+    it("allows you to use a filter") {
+      let template = Template(templateString: "{% filter uppercase %}Test{% endfilter %}")
+      let result = try template.render()
+      try expect(result) == "TEST"
+    }
+
+    it("allows you to chain filters") {
+      let template = Template(templateString: "{% filter lowercase|capitalize %}TEST{% endfilter %}")
+      let result = try template.render()
+      try expect(result) == "Test"
+    }
+
+    it("errors without a filter") {
+      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") {
+        guard let value = $0 as? String,
+          let argument = $1.first as? String else { return $0 }
+        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") {
+        guard let value = $0 as? String,
+          $1.count == 2,
+          let search = $1.first as? String,
+          let replacement = $1.last as? String else { return $0 }
+        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

@@ -1,95 +1,341 @@
 import Spectre
 @testable import Stencil
-import Foundation
+import XCTest
 
+final class ForNodeTests: XCTestCase {
+  let context = Context(dictionary: [
+    "items": [1, 2, 3],
+    "anyItems": [1, 2, 3] as [Any],
+    "nsItems": NSArray(array: [1, 2, 3]),
+    "emptyItems": [Int](),
+    "dict": [
+      "one": "I",
+      "two": "II"
+    ],
+    "tuples": [(1, 2, 3), (4, 5, 6)]
+  ])
 
-func testForNode() {
-  describe("ForNode") {
-    let context = Context(dictionary: [
-      "items": [1, 2, 3],
-      "emptyItems": [Int](),
-    ])
-
-    $0.it("renders the given nodes for each item") {
+  func testForNode() {
+    it("renders the given nodes for each item") {
       let nodes: [NodeType] = [VariableNode(variable: "item")]
-      let node = ForNode(resolvable: Variable("items"), loopVariable: "item", nodes: nodes, emptyNodes: [])
-      try expect(try node.render(context)) == "123"
+      let node = ForNode(resolvable: Variable("items"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      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 emptyNodes: [NodeType] = [TextNode(text: "empty")]
-      let node = ForNode(resolvable: Variable("emptyItems"), loopVariable: "item", nodes: nodes, emptyNodes: emptyNodes)
-      try expect(try node.render(context)) == "empty"
+      let node = ForNode(resolvable: Variable("anyItems"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      try expect(try node.render(self.context)) == "123"
     }
 
-    $0.it("renders a context variable of type Array<Any>") {
-      let any_context = Context(dictionary: [
-        "items": ([1, 2, 3] as [Any])
-      ])
-
+    #if os(OSX)
+    it("renders a context variable of type NSArray") {
       let nodes: [NodeType] = [VariableNode(variable: "item")]
-      let node = ForNode(resolvable: Variable("items"), loopVariable: "item", nodes: nodes, emptyNodes: [])
-      try expect(try node.render(any_context)) == "123"
+      let node = ForNode(resolvable: Variable("nsItems"), loopVariables: ["item"], nodes: nodes, emptyNodes: [])
+      try expect(try node.render(self.context)) == "123"
     }
+    #endif
 
-#if os(OSX)
-    $0.it("renders a context variable of type NSArray") {
-      let nsarray_context = Context(dictionary: [
-        "items": NSArray(array: [1, 2, 3])
-      ])
-
-      let nodes: [NodeType] = [VariableNode(variable: "item")]
-      let node = ForNode(resolvable: Variable("items"), loopVariable: "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") {
-      let nodes: [NodeType] = [VariableNode(variable: "item"), VariableNode(variable: "forloop.first")]
-      let node = ForNode(resolvable: Variable("items"), loopVariable: "item", nodes: nodes, emptyNodes: [])
-      try expect(try node.render(context)) == "1true2false3false"
-    }
-
-    $0.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"), loopVariable: "item", nodes: nodes, emptyNodes: [])
-      try expect(try node.render(context)) == "1false2false3true"
-    }
-
-    $0.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"), loopVariable: "item", nodes: nodes, emptyNodes: [])
-      try expect(try node.render(context)) == "112233"
-    }
-
-    $0.it("can render a filter") {
-      let templateString = "{% for article in ars|default:articles %}" +
-        "- {{ article.title }} by {{ article.author }}.\n" +
-        "{% endfor %}\n"
-
+    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"),
+          Article(title: "Memory Management with ARC", author: "Kyle Fuller")
         ]
       ])
-
-      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) == """
+        - Migrating from OCUnit to XCTest by Kyle Fuller.
+        - Memory Management with ARC by Kyle Fuller.
 
-      try expect(result) == fixture
+        """
     }
   }
+
+  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 parser = TokenParser(tokens: [], environment: Environment())
+      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
+
+        """
+    }
+
+    it("can iterate with less number of variables") {
+      let template = Template(templateString: """
+        {% 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
+
+        """
+    }
+
+    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: [])
+
+      try expect(try node.render(context)) == "123"
+    }
+
+    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: [])
+
+      try expect(try node.render(context)) == "123"
+    }
+
+    it("can iterate in range of variables") {
+      let template: Template = "{% for i in 1...j %}{{ i }}{% endfor %}"
+      try expect(try template.render(Context(dictionary: ["j": 3]))) == "123"
+    }
+  }
+
+  func testHandleInvalidInput() throws {
+    let token = Token.block(value: "for i", at: .unknown)
+    let parser = TokenParser(tokens: [token], environment: Environment())
+    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)
+  }
 }
 
+private struct MyStruct {
+  let string: String
+  let number: Int
+}
 
-fileprivate struct Article {
+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/IfNodeSpec.swift

@@ -1,107 +1,288 @@
 import Spectre
 @testable import Stencil
+import XCTest
 
+private struct SomeType {
+  let value: String? = nil
+}
 
-func testIfNode() {
-  describe("IfNode") {
-    $0.describe("parsing") {
-      $0.it("can parse an if block") {
-        let tokens: [Token] = [
-          .block(value: "if value"),
-          .text(value: "true"),
-          .block(value: "else"),
-          .text(value: "false"),
-          .block(value: "endif")
-        ]
+final class IfNodeTests: XCTestCase {
+  func testParseIf() {
+    it("can parse an if block") {
+      let tokens: [Token] = [
+        .block(value: "if value", at: .unknown),
+        .text(value: "true", at: .unknown),
+        .block(value: "endif", at: .unknown)
+      ]
 
-        let parser = TokenParser(tokens: tokens, namespace: Namespace())
-        let nodes = try parser.parse()
-        let node = nodes.first as? IfNode
-        let trueNode = node?.trueNodes.first as? TextNode
-        let falseNode = node?.falseNodes.first as? TextNode
+      let parser = TokenParser(tokens: tokens, environment: Environment())
+      let nodes = try parser.parse()
+      let node = nodes.first as? IfNode
 
-        try expect(nodes.count) == 1
-        try expect(node?.trueNodes.count) == 1
-        try expect(trueNode?.text) == "true"
-        try expect(node?.falseNodes.count) == 1
-        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: "else"),
-          .text(value: "false"),
-          .block(value: "endif")
-        ]
-
-        let parser = TokenParser(tokens: tokens, namespace: Namespace())
-        let nodes = try parser.parse()
-        let node = nodes.first as? IfNode
-        let trueNode = node?.trueNodes.first as? TextNode
-        let falseNode = node?.falseNodes.first as? TextNode
-
-        try expect(nodes.count) == 1
-        try expect(node?.trueNodes.count) == 1
-        try expect(trueNode?.text) == "true"
-        try expect(node?.falseNodes.count) == 1
-        try expect(falseNode?.text) == "false"
-      }
-
-      $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, namespace: Namespace())
-        let nodes = try parser.parse()
-        let node = nodes.first as? IfNode
-        let trueNode = node?.trueNodes.first as? TextNode
-        let falseNode = node?.falseNodes.first as? TextNode
-
-        try expect(nodes.count) == 1
-        try expect(node?.trueNodes.count) == 1
-        try expect(trueNode?.text) == "true"
-        try expect(node?.falseNodes.count) == 1
-        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, namespace: Namespace())
-        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, namespace: Namespace())
-        let error = TemplateSyntaxError("`endif` was not found.")
-        try expect(try parser.parse()).toThrow(error)
-      }
+      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.describe("rendering") {
-      $0.it("renders the truth when expression evaluates to true") {
-        let node = IfNode(expression: StaticExpression(value: true), trueNodes: [TextNode(text: "true")], falseNodes: [TextNode(text: "false")])
-        try expect(try node.render(Context())) == "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)
+      ]
 
-      $0.it("renders the false when expression evaluates to false") {
-        let node = IfNode(expression: StaticExpression(value: false), trueNodes: [TextNode(text: "true")], falseNodes: [TextNode(text: "false")])
-        try expect(try node.render(Context())) == "false"
-      }
+      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: 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"
+    }
+
+    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"
+    }
+
+    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"
+    }
+
+    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())) == ""
+    }
+  }
+
+  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"
+  }
 }

Tests/StencilTests/IncludeSpec.swift

@@ -1,60 +1,72 @@
+import PathKit
 import Spectre
 @testable import Stencil
-import PathKit
+import XCTest
 
+final class IncludeTests: XCTestCase {
+  let path = Path(#file as String) + ".." + "fixtures"
+  lazy var loader = FileSystemLoader(paths: [path])
+  lazy var environment = Environment(loader: loader)
 
-func testInclude() {
-  describe("Include") {
-    let path = Path(#file) + ".." + "fixtures"
-    let loader = FileSystemLoader(paths: [path])
+  func testParsing() {
+    it("throws an error when no template is given") {
+      let tokens: [Token] = [ .block(value: "include", at: .unknown) ]
+      let parser = TokenParser(tokens: tokens, environment: Environment())
 
-    $0.describe("parsing") {
-      $0.it("throws an error when no template is given") {
-        let tokens: [Token] = [ .block(value: "include") ]
-        let parser = TokenParser(tokens: tokens, namespace: Namespace())
+      let error = TemplateSyntaxError(reason: """
+        '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
+        """, token: tokens.first)
+      try expect(try parser.parse()).toThrow(error)
+    }
 
-        let error = TemplateSyntaxError("'include' tag takes one argument, the template file to be included")
-        try expect(try parser.parse()).toThrow(error)
-      }
+    it("can parse a valid include block") {
+      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 tokens: [Token] = [ .block(value: "include \"test.html\"") ]
-        let parser = TokenParser(tokens: tokens, namespace: Namespace())
+      let nodes = try parser.parse()
+      let node = nodes.first as? IncludeNode
+      try expect(nodes.count) == 1
+      try expect(node?.templateName) == Variable("\"test.html\"")
+    }
+  }
 
-        let nodes = try parser.parse()
-        let node = nodes.first as? IncludeNode
-        try expect(nodes.count) == 1
-        try expect(node?.templateName) == Variable("\"test.html\"")
+  func testRendering() {
+    it("throws an error when rendering without a loader") {
+      let node = IncludeNode(templateName: Variable("\"test.html\""), token: .block(value: "", at: .unknown))
+
+      do {
+        _ = try node.render(Context())
+      } catch {
+        try expect("\(error)") == "Template named `test.html` does not exist. No loaders found"
       }
     }
 
-    $0.describe("rendering") {
-      $0.it("throws an error when rendering without a loader") {
-        let node = IncludeNode(templateName: Variable("\"test.html\""))
+    it("throws an error when it cannot find the included template") {
+      let node = IncludeNode(templateName: Variable("\"unknown.html\""), token: .block(value: "", at: .unknown))
 
-        do {
-          _ = try node.render(Context())
-        } catch {
-          try expect("\(error)") == "Template loader not in context"
-        }
+      do {
+        _ = try node.render(Context(environment: self.environment))
+      } catch {
+        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") {
-        let node = IncludeNode(templateName: Variable("\"unknown.html\""))
+    it("successfully renders a found included template") {
+      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 {
-          _ = try node.render(Context(dictionary: ["loader": loader]))
-        } catch {
-          try expect("\(error)".hasPrefix("'unknown.html' template not found")).to.beTrue()
-        }
-      }
-
-      $0.it("successfully renders a found included template") {
-        let node = IncludeNode(templateName: Variable("\"test.html\""))
-        let context = Context(dictionary: ["loader":loader, "target": "World"])
-        let value = try node.render(context)
-        try expect(value) == "Hello World!"
-      }
+    it("successfully passes context") {
+      let template = Template(templateString: """
+        {% include "test.html" child %}
+        """)
+      let context = Context(dictionary: ["child": ["target": "World"]], environment: self.environment)
+      let value = try template.render(context)
+      try expect(value) == "Hello World!"
     }
   }
 }

Tests/StencilTests/InheritanceSpec.swift

@@ -0,0 +1,36 @@
+import PathKit
+import Spectre
+import Stencil
+import XCTest
+
+final class InheritanceTests: XCTestCase {
+  let path = Path(#file as String) + ".." + "fixtures"
+  lazy var loader = FileSystemLoader(paths: [path])
+  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
+        """
+    }
+  }
+}

Tests/StencilTests/InheritenceSpec.swift

@@ -1,23 +0,0 @@
-import Spectre
-import Stencil
-import PathKit
-
-
-func testInheritence() {
-  describe("Inheritence") {
-    let path = Path(#file) + ".." + "fixtures"
-    let loader = FileSystemLoader(paths: [path])
-
-    $0.it("can inherit from another template") {
-      let context = Context(dictionary: ["loader": loader])
-      let template = try loader.loadTemplate(name: "child.html")
-      try expect(try template?.render(context)) == "Header\nChild"
-    }
-
-    $0.it("can inherit from another template inheriting from another template") {
-      let context = Context(dictionary: ["loader": loader])
-      let template = try loader.loadTemplate(name: "child-child.html")
-      try expect(try template?.render(context)) == "Child Child Header\nChild"
-    }
-  }
-}

Tests/StencilTests/LexerSpec.swift

@@ -1,50 +1,144 @@
+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() {
-  describe("Lexer") {
-    $0.it("can tokenize text") {
-      let lexer = Lexer(templateString: "Hello World")
-      let tokens = lexer.tokenize()
+    try expect(tokens.count) == 1
+    try expect(tokens.first) == .text(value: "Hello World", at: makeSourceMap("Hello World", for: lexer))
+  }
 
-      try expect(tokens.count) == 1
-      try expect(tokens.first) == .text(value: "Hello World")
-    }
+  func testComment() throws {
+    let lexer = Lexer(templateString: "{# Comment #}")
+    let tokens = lexer.tokenize()
 
-    $0.it("can tokenize a comment") {
-      let lexer = Lexer(templateString: "{# Comment #}")
-      let tokens = lexer.tokenize()
+    try expect(tokens.count) == 1
+    try expect(tokens.first) == .comment(value: "Comment", at: makeSourceMap("Comment", for: lexer))
+  }
 
-      try expect(tokens.count) == (1)
-      try expect(tokens.first) == .comment(value: "Comment")
-    }
+  func testVariable() throws {
+    let lexer = Lexer(templateString: "{{ Variable }}")
+    let tokens = lexer.tokenize()
 
-    $0.it("can tokenize a variable") {
-      let lexer = Lexer(templateString: "{{ Variable }}")
-      let tokens = lexer.tokenize()
+    try expect(tokens.count) == 1
+    try expect(tokens.first) == .variable(value: "Variable", at: makeSourceMap("Variable", for: lexer))
+  }
 
-      try expect(tokens.count) == 1
-      try expect(tokens.first) == .variable(value: "Variable")
-    }
+  func testTokenWithoutSpaces() throws {
+    let lexer = Lexer(templateString: "{{Variable}}")
+    let tokens = lexer.tokenize()
 
-    $0.it("can tokenize a mixture of content") {
-      let lexer = Lexer(templateString: "My name is {{ name }}.")
-      let tokens = lexer.tokenize()
+    try expect(tokens.count) == 1
+    try expect(tokens.first) == .variable(value: "Variable", at: makeSourceMap("Variable", for: lexer))
+  }
 
-      try expect(tokens.count) == 3
-      try expect(tokens[0]) == Token.text(value: "My name is ")
-      try expect(tokens[1]) == Token.variable(value: "name")
-      try expect(tokens[2]) == Token.text(value: ".")
-    }
+  func testUnclosedTag() throws {
+    let templateString = "{{ thing"
+    let lexer = Lexer(templateString: templateString)
+    let tokens = lexer.tokenize()
 
-    $0.it("can tokenize two variables without being greedy") {
-      let lexer = Lexer(templateString: "{{ thing }}{{ name }}")
-      let tokens = lexer.tokenize()
+    try expect(tokens.count) == 1
+    try expect(tokens.first) == .text(value: "", at: makeSourceMap("{{ thing", for: lexer))
+  }
 
-      try expect(tokens.count) == 2
-      try expect(tokens[0]) == Token.variable(value: "thing")
-      try expect(tokens[1]) == Token.variable(value: "name")
+  func testContentMixture() throws {
+    let templateString = "My name is {{ myname }}."
+    let lexer = Lexer(templateString: templateString)
+    let tokens = lexer.tokenize()
+
+    try expect(tokens.count) == 3
+    try expect(tokens[0]) == Token.text(value: "My name is ", at: makeSourceMap("My name is ", for: lexer))
+    try expect(tokens[1]) == Token.variable(value: "myname", at: makeSourceMap("myname", for: lexer))
+    try expect(tokens[2]) == Token.text(value: ".", at: makeSourceMap(".", for: lexer))
+  }
+
+  func testVariablesWithoutBeingGreedy() throws {
+    let templateString = "{{ thing }}{{ name }}"
+    let lexer = Lexer(templateString: templateString)
+    let tokens = lexer.tokenize()
+
+    try expect(tokens.count) == 2
+    try expect(tokens[0]) == Token.variable(value: "thing", at: makeSourceMap("thing", for: lexer))
+    try expect(tokens[1]) == Token.variable(value: "name", at: makeSourceMap("name", for: lexer))
+  }
+
+  func testUnclosedBlock() throws {
+    let lexer = Lexer(templateString: "{%}")
+    _ = 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 {
+    let templateString = """
+      My name is {%
+          if name
+           and
+          name
+      %}{{
+      name
+      }}{%
+      endif %}.
+      """
+    let lexer = Lexer(templateString: templateString)
+    let tokens = lexer.tokenize()
+
+    try expect(tokens.count) == 5
+    try expect(tokens[0]) == Token.text(value: "My name is ", at: makeSourceMap("My name is", for: lexer))
+    try expect(tokens[1]) == Token.block(value: "if name and name", at: makeSourceMap("{%", for: lexer))
+    try expect(tokens[2]) == Token.variable(value: "name", at: makeSourceMap("name", for: lexer, options: .backwards))
+    try expect(tokens[3]) == Token.block(value: "endif", at: makeSourceMap("endif", for: lexer))
+    try expect(tokens[4]) == Token.text(value: ".", at: makeSourceMap(".", for: lexer))
+  }
+
+  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]) == Token.text(value: "class Some ", at: makeSourceMap("class Some ", for: lexer))
+    try expect(tokens[1]) == Token.variable(value: "'{'", at: makeSourceMap("'{'", for: lexer))
+    try expect(tokens[2]) == Token.block(value: "if true", at: makeSourceMap("if true", for: lexer))
+    try expect(tokens[3]) == Token.variable(value: "stuff", at: makeSourceMap("stuff", for: lexer))
+    try expect(tokens[4]) == Token.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

@@ -0,0 +1,55 @@
+import PathKit
+import Spectre
+import Stencil
+import XCTest
+
+final class TemplateLoaderTests: XCTestCase {
+  func testFileSystemLoader() {
+    let path = Path(#file as String) + ".." + "fixtures"
+    let loader = FileSystemLoader(paths: [path])
+    let environment = Environment(loader: loader)
+
+    it("errors when a template cannot be found") {
+      try expect(try environment.loadTemplate(name: "unknown.html")).toThrow()
+    }
+
+    it("errors when an array of templates cannot be found") {
+      try expect(try environment.loadTemplate(names: ["unknown.html", "unknown2.html"])).toThrow()
+    }
+
+    it("can load a template from a file") {
+      _ = try environment.loadTemplate(name: "test.html")
+    }
+
+    it("errors when loading absolute file outside of the selected path") {
+      try expect(try environment.loadTemplate(name: "/etc/hosts")).toThrow()
+    }
+
+    it("errors when loading relative file outside of the selected path") {
+      try expect(try environment.loadTemplate(name: "../LoaderSpec.swift")).toThrow()
+    }
+  }
+
+  func testDictionaryLoader() {
+    let loader = DictionaryLoader(templates: [
+        "index.html": "Hello World"
+    ])
+    let environment = Environment(loader: loader)
+
+    it("errors when a template cannot be found") {
+      try expect(try environment.loadTemplate(name: "unknown.html")).toThrow()
+    }
+
+    it("errors when an array of templates cannot be found") {
+      try expect(try environment.loadTemplate(names: ["unknown.html", "unknown2.html"])).toThrow()
+    }
+
+    it("can load a template from a known templates") {
+      _ = try environment.loadTemplate(name: "index.html")
+    }
+
+    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 +1,62 @@
 import Spectre
-import Stencil
+@testable import Stencil
+import XCTest
 
+class ErrorNode: NodeType {
+  let token: Token?
+  init(token: Token? = nil) {
+    self.token = token
+  }
 
-class ErrorNode : NodeType {
   func render(_ context: Context) throws -> String {
     throw TemplateSyntaxError("Custom Error")
   }
 }
 
+final class NodeTests: XCTestCase {
+  let context = Context(dictionary: [
+    "name": "Kyle",
+    "age": 27,
+    "items": [1, 2, 3]
+  ])
 
-func testNode() {
-  describe("Node") {
-    let context = Context(dictionary: [
-      "name": "Kyle",
-      "age": 27,
-      "items": [1, 2, 3],
-    ])
+  func testTextNode() {
+    it("renders the given text") {
+      let node = TextNode(text: "Hello World")
+      try expect(try node.render(self.context)) == "Hello World"
+    }
+  }
 
-    $0.describe("TextNode") {
-      $0.it("renders the given text") {
-        let node = TextNode(text: "Hello World")
-        try expect(try node.render(context)) == "Hello World"
-      }
+  func testVariableNode() {
+    it("resolves and renders the variable") {
+      let node = VariableNode(variable: Variable("name"))
+      try expect(try node.render(self.context)) == "Kyle"
     }
 
-    $0.describe("VariableNode") {
-      $0.it("resolves and renders the variable") {
-        let node = VariableNode(variable: Variable("name"))
-        try expect(try node.render(context)) == "Kyle"
-      }
+    it("resolves and renders a non string variable") {
+      let node = VariableNode(variable: Variable("age"))
+      try expect(try node.render(self.context)) == "27"
+    }
+  }
 
-      $0.it("resolves and renders a non string variable") {
-        let node = VariableNode(variable: Variable("age"))
-        try expect(try node.render(context)) == "27"
-      }
+  func testRendering() {
+    it("renders the nodes") {
+      let nodes: [NodeType] = [
+        TextNode(text: "Hello "),
+        VariableNode(variable: "name")
+      ]
+
+      try expect(try renderNodes(nodes, self.context)) == "Hello Kyle"
     }
 
-    $0.describe("rendering nodes") {
-      $0.it("renders the nodes") {
-        let nodes: [NodeType] = [
-          TextNode(text:"Hello "),
-          VariableNode(variable: "name"),
-        ]
+    it("correctly throws a nodes failure") {
+      let nodes: [NodeType] = [
+        TextNode(text: "Hello "),
+        VariableNode(variable: "name"),
+        ErrorNode()
+      ]
 
-        try expect(try renderNodes(nodes, context)) == "Hello Kyle"
-      }
-
-      $0.it("correctly throws a nodes failure") {
-        let nodes: [NodeType] = [
-          TextNode(text:"Hello "),
-          VariableNode(variable: "name"),
-          ErrorNode(),
-        ]
-
-        try expect(try renderNodes(nodes, context)).toThrow(TemplateSyntaxError("Custom Error"))
-      }
+      try expect(try renderNodes(nodes, self.context)).toThrow(TemplateSyntaxError("Custom Error"))
     }
   }
 }

Tests/StencilTests/NowNodeSpec.swift

@@ -1,43 +1,50 @@
-import Foundation
 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() {
-#if !os(Linux)
-  describe("NowNode") {
-    $0.describe("parsing") {
-      $0.it("parses default format without any now arguments") {
-        let tokens: [Token] = [ .block(value: "now") ]
-        let parser = TokenParser(tokens: tokens, namespace: Namespace())
-
-        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, namespace: Namespace())
-        let nodes = try parser.parse()
-        let node = nodes.first as? NowNode
-        try expect(nodes.count) == 1
-        try expect(node?.format.variable) == "\"HH:mm\""
-      }
+      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\""
+#endif
     }
 
-    $0.describe("rendering") {
-      $0.it("renders the date") {
-        let node = NowNode(format: Variable("\"yyyy-MM-dd\""))
-
-        let formatter = DateFormatter()
-        formatter.dateFormat = "yyyy-MM-dd"
-        let date = formatter.string(from: NSDate() as Date)
-
-        try expect(try node.render(Context())) == date
-      }
+    it("parses now with a format") {
+#if os(Linux)
+      throw skip()
+#else
+      let tokens: [Token] = [ .block(value: "now \"HH:mm\"", at: .unknown) ]
+      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\""
+#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: NSDate() as Date)
+
+      try expect(try node.render(Context())) == date
 #endif
+    }
+  }
 }

Tests/StencilTests/ParserSpec.swift

@@ -1,13 +1,13 @@
 import Spectre
-import Stencil
+@testable import Stencil
+import XCTest
 
-
-func testTokenParser() {
-  describe("TokenParser") {
-    $0.it("can parse a text token") {
+final class TokenParserTests: XCTestCase {
+  func testTokenParser() {
+    it("can parse a text token") {
       let parser = TokenParser(tokens: [
-        .text(value: "Hello World")
-      ], namespace: Namespace())
+        .text(value: "Hello World", at: .unknown)
+      ], environment: Environment())
 
       let nodes = try parser.parse()
       let node = nodes.first as? TextNode
@@ -16,10 +16,10 @@ func testTokenParser() {
       try expect(node?.text) == "Hello World"
     }
 
-    $0.it("can parse a variable token") {
+    it("can parse a variable token") {
       let parser = TokenParser(tokens: [
-        .variable(value: "'name'")
-      ], namespace: Namespace())
+        .variable(value: "'name'", at: .unknown)
+      ], environment: Environment())
 
       let nodes = try parser.parse()
       let node = nodes.first as? VariableNode
@@ -28,35 +28,37 @@ func testTokenParser() {
       try expect(result) == "name"
     }
 
-    $0.it("can parse a comment token") {
+    it("can parse a comment token") {
       let parser = TokenParser(tokens: [
-        .comment(value: "Secret stuff!")
-      ], namespace: Namespace())
+        .comment(value: "Secret stuff!", at: .unknown)
+      ], environment: Environment())
 
       let nodes = try parser.parse()
       try expect(nodes.count) == 0
     }
 
-    $0.it("can parse a tag token") {
-      let namespace = Namespace()
-      namespace.registerSimpleTag("known") { _ in
-        return ""
+    it("can parse a tag token") {
+      let simpleExtension = Extension()
+      simpleExtension.registerSimpleTag("known") { _ in
+        ""
       }
 
       let parser = TokenParser(tokens: [
-        .block(value: "known"),
-      ], namespace: namespace)
+        .block(value: "known", at: .unknown)
+      ], environment: Environment(extensions: [simpleExtension]))
 
       let nodes = try parser.parse()
       try expect(nodes.count) == 1
     }
 
-    $0.it("errors when parsing an unknown tag") {
-      let parser = TokenParser(tokens: [
-        .block(value: "unknown"),
-      ], namespace: Namespace())
+    it("errors when parsing an unknown tag") {
+      let tokens: [Token] = [.block(value: "unknown", at: .unknown)]
+      let parser = TokenParser(tokens: tokens, environment: Environment())
 
-      try expect(try parser.parse()).toThrow(TemplateSyntaxError("Unknown template tag 'unknown'"))
+      try expect(try parser.parse()).toThrow(TemplateSyntaxError(
+        reason: "Unknown template tag 'unknown'",
+        token: tokens.first)
+      )
     }
   }
 }

Tests/StencilTests/StencilSpec.swift

@@ -1,72 +1,68 @@
 import Spectre
 import Stencil
+import XCTest
 
-
-fileprivate class CustomNode : NodeType {
-  func render(_ context:Context) throws -> String {
+private struct CustomNode: NodeType {
+  let token: Token?
+  func render(_ context: Context) throws -> String {
     return "Hello World"
   }
 }
 
-
-fileprivate struct Article {
+private struct Article {
   let title: String
   let author: String
 }
 
+final class StencilTests: XCTestCase {
+  lazy var environment: Environment = {
+    let exampleExtension = Extension()
+    exampleExtension.registerSimpleTag("simpletag") { _ in
+      "Hello World"
+    }
+    exampleExtension.registerTag("customtag") { _, token in
+      CustomNode(token: token)
+    }
+    return Environment(extensions: [exampleExtension])
+  }()
 
-func testStencil() {
-  describe("Stencil") {
-    $0.it("can render the README example") {
+  func testStencil() {
+    it("can render the README example") {
+      let templateString = """
+        There are {{ articles.count }} articles.
 
-      let templateString = "There are {{ articles.count }} articles.\n" +
-        "\n" +
-        "{% for article in articles %}" +
-        "    - {{ article.title }} by {{ article.author }}.\n" +
-        "{% endfor %}\n"
+        {% for article in articles %}\
+            - {{ article.title }} by {{ article.author }}.
+        {% endfor %}
+        """
 
-      let context = Context(dictionary: [
+      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" +
-        "\n" +
-        "    - Migrating from OCUnit to XCTest by Kyle Fuller.\n" +
-        "    - Memory Management with ARC by Kyle Fuller.\n" +
-        "\n"
+      try expect(result) == """
+        There are 2 articles.
 
-      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") {
-      let templateString = "{% custom %}"
-      let template = Template(templateString: templateString)
-
-      let namespace = Namespace()
-      namespace.registerTag("custom") { parser, token in
-        return CustomNode()
-      }
-
-      let result = try template.render(Context(namespace: namespace))
+    it("can render a custom template tag") {
+      let result = try self.environment.renderTemplate(string: "{% customtag %}")
       try expect(result) == "Hello World"
     }
 
-    $0.it("can render a simple custom tag") {
-      let templateString = "{% custom %}"
-      let template = Template(templateString: templateString)
-
-      let namespace = Namespace()
-      namespace.registerSimpleTag("custom") { context in
-        return "Hello World"
-      }
-
-      try expect(try template.render(Context(namespace: namespace))) == "Hello World"
+    it("can render a simple custom tag") {
+      let result = try self.environment.renderTemplate(string: "{% simpletag %}")
+      try expect(result) == "Hello World"
     }
   }
 }

Tests/StencilTests/TemplateLoaderSpec.swift

@@ -1,25 +0,0 @@
-import Spectre
-import Stencil
-import PathKit
-
-
-func testTemplateLoader() {
-  describe("TemplateLoader") {
-    let path = Path(#file) + ".."  + "fixtures"
-    let loader = FileSystemLoader(paths: [path])
-
-    $0.it("returns nil when a template cannot be found") {
-      try expect(try loader.loadTemplate(name: "unknown.html")).to.beNil()
-    }
-
-    $0.it("returns nil when an array of templates cannot be found") {
-      try expect(try loader.loadTemplate(names: ["unknown.html", "unknown2.html"])).to.beNil()
-    }
-
-    $0.it("can load a template from a file") {
-      if try loader.loadTemplate(name: "test.html") == nil {
-        throw failure("didn't find the template")
-      }
-    }
-  }
-}

Tests/StencilTests/TemplateSpec.swift

@@ -1,20 +1,18 @@
 import Spectre
-import Stencil
+@testable import Stencil
+import XCTest
 
-
-func testTemplate() {
-  describe("Template") {
-    $0.it("can render a template from a string") {
-      let context = Context(dictionary: [ "name": "Kyle" ])
+final class TemplateTests: XCTestCase {
+  func testTemplate() {
+    it("can render a template from a string") {
       let template = Template(templateString: "Hello World")
-      let result = try template.render(context)
+      let result = try template.render([ "name": "Kyle" ])
       try expect(result) == "Hello World"
     }
 
-    $0.it("can render a template from a string literal") {
-        let context = Context(dictionary: [ "name": "Kyle" ])
+    it("can render a template from a string literal") {
         let template: Template = "Hello World"
-        let result = try template.render(context)
+        let result = try template.render([ "name": "Kyle" ])
         try expect(result) == "Hello World"
     }
   }

Tests/StencilTests/TokenSpec.swift

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

Tests/StencilTests/VariableSpec.swift

@@ -1,106 +1,367 @@
-import Foundation
 import Spectre
-import Stencil
-
+@testable import Stencil
+import XCTest
 
 #if os(OSX)
-@objc class Object : NSObject {
-  let title = "Hello World"
+@objc
+class Superclass: NSObject {
+  @objc let name = "Foo"
+}
+@objc
+class Object: Superclass {
+  @objc let title = "Hello World"
 }
 #endif
 
-fileprivate struct Person {
+private struct Person {
   let name: String
 }
 
-fileprivate struct Article {
+private struct Article {
   let author: Person
 }
 
+private class WebSite {
+  let url: String = "blog.com"
+}
 
-func testVariable() {
-  describe("Variable") {
-    let context = Context(dictionary: [
+private class Blog: WebSite {
+  let articles: [Article] = [Article(author: Person(name: "Kyle"))]
+  let featuring: Article? = Article(author: Person(name: "Jhon"))
+}
+
+final class VariableTests: XCTestCase {
+  let context: Context = {
+    let ext = Extension()
+    ext.registerFilter("incr") { arg in
+      (arg.flatMap { toNumber(value: $0) } ?? 0) + 1
+    }
+    let environment = Environment(extensions: [ext])
+
+    var context = Context(dictionary: [
       "name": "Kyle",
       "contacts": ["Katie", "Carlton"],
       "profiles": [
-        "github": "kylef",
+        "github": "kylef"
       ],
-      "article": Article(author: Person(name: "Kyle"))
-    ])
-
+      "counter": [
+        "count": "kylef"
+      ],
+      "article": Article(author: Person(name: "Kyle")),
+      "blog": Blog(),
+      "tuple": (one: 1, two: 2)
+    ], environment: environment)
 #if os(OSX)
     context["object"] = Object()
 #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"
     }
+    
+    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()
+    }
 
-    $0.it("can resolve a string literal with single quotes") {
+    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"
     }
+    
+    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(self.context) as? Int
+      try expect(result) == 5
+    }
 
-    $0.it("can resolve a string variable") {
+    it("can resolve an float literal") {
+      let variable = Variable("3.14")
+      let result = try variable.resolve(self.context) as? Number
+      try expect(result) == 3.14
+    }
+
+    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 result1 = try variable1.resolve(context) as? String
+        let result1 = try variable1.resolve(self.context) as? String
         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 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"
     }
 
+    it("can resolve a value via reflection") {
+      let variable = Variable("blog.articles.0.author.name")
+      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)
-    $0.it("can resolve a value via KVO") {
+    it("can resolve a value via KVO") {
       let variable = Variable("object.title")
-      let result = try variable.resolve(context) as? String
+      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
+    }
+
+    it("can resolve tuple by label") {
+      let variable = Variable("tuple.two")
+      let result = try variable.resolve(self.context) as? Int
+      try expect(result) == 2
+    }
+  }
+
+  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()
+    }
+  }
 }

Tests/StencilTests/XCTest.swift

@@ -1,28 +0,0 @@
-import XCTest
-
-
-public func stencilTests() {
-  testContext()
-  testFilter()
-  testLexer()
-  testToken()
-  testTokenParser()
-  testTemplateLoader()
-  testTemplate()
-  testVariable()
-  testNode()
-  testForNode()
-  testExpressions()
-  testIfNode()
-  testNowNode()
-  testInclude()
-  testInheritence()
-  testStencil()
-}
-
-
-class StencilTests: XCTestCase {
-  func testRunStencilTests() {
-    stencilTests()
-  }
-}

Tests/StencilTests/XCTestManifests.swift

@@ -0,0 +1,228 @@
+import XCTest
+
+extension ContextTests {
+    static let __allTests = [
+        ("testContextRestoration", testContextRestoration),
+        ("testContextSubscripting", testContextSubscripting),
+    ]
+}
+
+extension EnvironmentBaseAndChildTemplateTests {
+    static let __allTests = [
+        ("testRuntimeErrorInBaseTemplate", testRuntimeErrorInBaseTemplate),
+        ("testRuntimeErrorInChildTemplate", testRuntimeErrorInChildTemplate),
+        ("testSyntaxErrorInBaseTemplate", testSyntaxErrorInBaseTemplate),
+        ("testSyntaxErrorInChildTemplate", testSyntaxErrorInChildTemplate),
+    ]
+}
+
+extension EnvironmentIncludeTemplateTests {
+    static let __allTests = [
+        ("testRuntimeError", testRuntimeError),
+        ("testSyntaxError", testSyntaxError),
+    ]
+}
+
+extension EnvironmentTests {
+    static let __allTests = [
+        ("testLoading", testLoading),
+        ("testRendering", testRendering),
+        ("testRenderingError", testRenderingError),
+        ("testSyntaxError", testSyntaxError),
+        ("testUnknownFilter", testUnknownFilter),
+    ]
+}
+
+extension ExpressionsTests {
+    static let __allTests = [
+        ("testAndExpression", testAndExpression),
+        ("testEqualityExpression", testEqualityExpression),
+        ("testExpressionParsing", testExpressionParsing),
+        ("testFalseExpressions", testFalseExpressions),
+        ("testFalseInExpression", testFalseInExpression),
+        ("testInequalityExpression", testInequalityExpression),
+        ("testLessThanEqualExpression", testLessThanEqualExpression),
+        ("testLessThanExpression", testLessThanExpression),
+        ("testMoreThanEqualExpression", testMoreThanEqualExpression),
+        ("testMoreThanExpression", testMoreThanExpression),
+        ("testMultipleExpressions", testMultipleExpressions),
+        ("testNotExpression", testNotExpression),
+        ("testOrExpression", testOrExpression),
+        ("testTrueExpressions", testTrueExpressions),
+        ("testTrueInExpression", testTrueInExpression),
+    ]
+}
+
+extension FilterTagTests {
+    static let __allTests = [
+        ("testFilterTag", testFilterTag),
+    ]
+}
+
+extension FilterTests {
+    static let __allTests = [
+        ("testDefaultFilter", testDefaultFilter),
+        ("testDynamicFilters", testDynamicFilters),
+        ("testFilterSuggestion", testFilterSuggestion),
+        ("testIndentContent", testIndentContent),
+        ("testIndentFirstLine", testIndentFirstLine),
+        ("testIndentNotEmptyLines", testIndentNotEmptyLines),
+        ("testIndentWithArbitraryCharacter", testIndentWithArbitraryCharacter),
+        ("testJoinFilter", testJoinFilter),
+        ("testRegistration", testRegistration),
+        ("testRegistrationOverrideDefault", testRegistrationOverrideDefault),
+        ("testRegistrationWithArguments", testRegistrationWithArguments),
+        ("testSplitFilter", testSplitFilter),
+        ("testStringFilters", testStringFilters),
+        ("testStringFiltersWithArrays", testStringFiltersWithArrays),
+    ]
+}
+
+extension ForNodeTests {
+    static let __allTests = [
+        ("testArrayOfTuples", testArrayOfTuples),
+        ("testForNode", testForNode),
+        ("testHandleInvalidInput", testHandleInvalidInput),
+        ("testIterateDictionary", testIterateDictionary),
+        ("testIterateRange", testIterateRange),
+        ("testIterateUsingMirroring", testIterateUsingMirroring),
+        ("testLoopMetadata", testLoopMetadata),
+        ("testWhereExpression", testWhereExpression),
+    ]
+}
+
+extension IfNodeTests {
+    static let __allTests = [
+        ("testEvaluatesNilAsFalse", testEvaluatesNilAsFalse),
+        ("testParseIf", testParseIf),
+        ("testParseIfnot", testParseIfnot),
+        ("testParseIfWithElif", testParseIfWithElif),
+        ("testParseIfWithElifWithoutElse", testParseIfWithElifWithoutElse),
+        ("testParseIfWithElse", testParseIfWithElse),
+        ("testParseMultipleElif", testParseMultipleElif),
+        ("testParsingErrors", testParsingErrors),
+        ("testRendering", testRendering),
+        ("testSupportsRangeVariables", testSupportsRangeVariables),
+        ("testSupportVariableFilters", testSupportVariableFilters),
+    ]
+}
+
+extension IncludeTests {
+    static let __allTests = [
+        ("testParsing", testParsing),
+        ("testRendering", testRendering),
+    ]
+}
+
+extension InheritanceTests {
+    static let __allTests = [
+        ("testInheritance", testInheritance),
+    ]
+}
+
+extension LexerTests {
+    static let __allTests = [
+        ("testComment", testComment),
+        ("testContentMixture", testContentMixture),
+        ("testEmptyVariable", testEmptyVariable),
+        ("testEscapeSequence", testEscapeSequence),
+        ("testNewlines", testNewlines),
+        ("testPerformance", testPerformance),
+        ("testText", testText),
+        ("testTokenizeIncorrectSyntaxWithoutCrashing", testTokenizeIncorrectSyntaxWithoutCrashing),
+        ("testTokenWithoutSpaces", testTokenWithoutSpaces),
+        ("testUnclosedBlock", testUnclosedBlock),
+        ("testUnclosedTag", testUnclosedTag),
+        ("testVariable", testVariable),
+        ("testVariablesWithoutBeingGreedy", testVariablesWithoutBeingGreedy),
+    ]
+}
+
+extension NodeTests {
+    static let __allTests = [
+        ("testRendering", testRendering),
+        ("testTextNode", testTextNode),
+        ("testVariableNode", testVariableNode),
+    ]
+}
+
+extension NowNodeTests {
+    static let __allTests = [
+        ("testParsing", testParsing),
+        ("testRendering", testRendering),
+    ]
+}
+
+extension StencilTests {
+    static let __allTests = [
+        ("testStencil", testStencil),
+    ]
+}
+
+extension TemplateLoaderTests {
+    static let __allTests = [
+        ("testDictionaryLoader", testDictionaryLoader),
+        ("testFileSystemLoader", testFileSystemLoader),
+    ]
+}
+
+extension TemplateTests {
+    static let __allTests = [
+        ("testTemplate", testTemplate),
+    ]
+}
+
+extension TokenParserTests {
+    static let __allTests = [
+        ("testTokenParser", testTokenParser),
+    ]
+}
+
+extension TokenTests {
+    static let __allTests = [
+        ("testToken", testToken),
+    ]
+}
+
+extension VariableTests {
+    static let __allTests = [
+        ("testArray", testArray),
+        ("testDictionary", testDictionary),
+        ("testKVO", testKVO),
+        ("testLiterals", testLiterals),
+        ("testMultipleSubscripting", testMultipleSubscripting),
+        ("testOptional", testOptional),
+        ("testRangeVariable", testRangeVariable),
+        ("testReflection", testReflection),
+        ("testSubscripting", testSubscripting),
+        ("testTuple", testTuple),
+        ("testVariable", testVariable),
+    ]
+}
+
+#if !os(macOS)
+public func __allTests() -> [XCTestCaseEntry] {
+    return [
+        testCase(ContextTests.__allTests),
+        testCase(EnvironmentBaseAndChildTemplateTests.__allTests),
+        testCase(EnvironmentIncludeTemplateTests.__allTests),
+        testCase(EnvironmentTests.__allTests),
+        testCase(ExpressionsTests.__allTests),
+        testCase(FilterTagTests.__allTests),
+        testCase(FilterTests.__allTests),
+        testCase(ForNodeTests.__allTests),
+        testCase(IfNodeTests.__allTests),
+        testCase(IncludeTests.__allTests),
+        testCase(InheritanceTests.__allTests),
+        testCase(LexerTests.__allTests),
+        testCase(NodeTests.__allTests),
+        testCase(NowNodeTests.__allTests),
+        testCase(StencilTests.__allTests),
+        testCase(TemplateLoaderTests.__allTests),
+        testCase(TemplateTests.__allTests),
+        testCase(TokenParserTests.__allTests),
+        testCase(TokenTests.__allTests),
+        testCase(VariableTests.__allTests),
+    ]
+}
+#endif

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-super.html

@@ -0,0 +1,3 @@
+{% extends "base.html" %}
+{% 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/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/api.rst

@@ -0,0 +1,150 @@
+Template API
+============
+
+This document describes Stencils Swift API, and not the Swift template language.
+
+.. contents:: :depth: 2
+
+Environment
+-----------
+
+An environment contains shared configuration such as custom filters and tags
+along with template loaders.
+
+.. code-block:: swift
+
+    let environment = Environment()
+
+You can optionally provide a loader or extensions when creating an environment:
+
+.. code-block:: swift
+
+    let environment = Environment(loader: ..., extensions: [...])
+
+Rendering a Template
+~~~~~~~~~~~~~~~~~~~~
+
+Environment provides convinience methods to render a template either from a
+string or a template loader.
+
+.. code-block:: swift
+
+    let template = "Hello {{ name }}"
+    let context = ["name": "Kyle"]
+    let rendered = environment.renderTemplate(string: template, context: context)
+
+Rendering a template from the configured loader:
+
+.. code-block:: swift
+
+    let context = ["name": "Kyle"]
+    let rendered = environment.renderTemplate(name: "example.html", context: context)
+
+Loading a Template
+~~~~~~~~~~~~~~~~~~
+
+Environment provides an API to load a template from the configured loader.
+
+.. code-block:: swift
+
+    let template = try environment.loadTemplate(name: "example.html")
+
+Loader
+------
+
+Loaders are responsible for loading templates from a resource such as the file
+system.
+
+Stencil provides a ``FileSytemLoader`` which allows you to load a template
+directly from the file system.
+
+FileSystemLoader
+~~~~~~~~~~~~~~~~
+
+Loads templates from the file system. This loader can find templates in folders
+on the file system.
+
+.. code-block:: swift
+
+    FileSystemLoader(paths: ["./templates"])
+
+.. code-block:: swift
+
+    FileSystemLoader(bundle: [Bundle.main])
+
+
+DictionaryLoader
+~~~~~~~~~~~~~~~~
+
+Loads templates from a dictionary.
+
+.. code-block:: swift
+
+    DictionaryLoader(templates: ["index.html": "Hello World"])
+
+
+Custom Loaders
+~~~~~~~~~~~~~~
+
+``Loader`` is a protocol, so you can implement your own compatible loaders. You
+will need to implement a ``loadTemplate`` method to load the template,
+throwing a ``TemplateDoesNotExist`` when the template is not found.
+
+.. code-block:: swift
+
+    class ExampleMemoryLoader: Loader {
+      func loadTemplate(name: String, environment: Environment) throws -> Template {
+        if name == "index.html" {
+          return Template(templateString: "Hello", environment: environment)
+        }
+
+        throw TemplateDoesNotExist(name: name, loader: self)
+      }
+    }
+
+
+Context
+-------
+
+A ``Context`` is a structure containing any templates you would like to use in
+a template. It’s somewhat like a dictionary, however you can push and pop to
+scope variables. So that means that when iterating over a for loop, you can
+push a new scope into the context to store any variables local to the scope.
+
+You would normally only access the ``Context`` within a custom template tag or
+filter.
+
+Subscripting
+~~~~~~~~~~~~
+
+You can use subscripting to get and set values from the context.
+
+.. code-block:: swift
+
+    context["key"] = value
+    let value = context["key"]
+
+``push()``
+~~~~~~~~~~
+
+A ``Context`` is a stack. You can push a new level onto the ``Context`` so that
+modifications can easily be poped off. This is useful for isolating mutations
+into scope of a template tag. Such as ``{% if %}`` and ``{% for %}`` tags.
+
+.. code-block:: swift
+
+    context.push(["name": "example"]) {
+        // context contains name which is `example`.
+    }
+
+    // name is popped off the context after the duration of the closure.
+
+``flatten()``
+~~~~~~~~~~~~~
+
+Using ``flatten()`` method you can get whole ``Context`` stack as one
+dictionary including all variables.
+
+.. code-block:: swift
+
+    let dictionary = context.flatten()

docs/api/context.rst

@@ -1,51 +0,0 @@
-Context
-=======
-
-A Context is a structure containing any templates you would like to use in a
-template. It’s somewhat like a dictionary, however you can push and pop to
-scope variables. So that means that when iterating over a for loop, you can
-push a new scope into the context to store any variables local to the scope.
-
-You can initialise a ``Context`` with a ``Dictionary``.
-
-.. code-block:: swift
-
-    Context(dictionary: [String: Any]? = nil)
-
-API
-----
-
-Subscripting
-~~~~~~~~~~~~
-
-You can use subscripting to get and set values from the context.
-
-.. code-block:: swift
-
-    context["key"] = value
-    let value = context["key"]
-
-``push()``
-~~~~~~~~~~
-
-A ``Context`` is a stack. You can push a new level onto the ``Context`` so that
-modifications can easily be poped off. This is useful for isolating mutations
-into scope of a template tag. Such as ``{% if %}`` and ``{% for %}`` tags.
-
-.. code-block:: swift
-
-    context.push(["name": "example"]) {
-        // context contains name which is `example`.
-    }
-
-    // name is popped off the context after the duration of the closure.
-
-``flatten()``
-~~~~~~~~~~~~~
-
-Using ``flatten()`` method you can get whole ``Context`` stack as one
-dictionary including all variables.
-
-.. code-block:: swift
-
-    let dictionary = context.flatten()

docs/builtins.rst

@@ -19,6 +19,39 @@ A for loop allows you to iterate over an array found by variable lookup.
       {% endfor %}
     </ul>
 
+The ``for`` tag can iterate over dictionaries.
+
+.. code-block:: html+django
+
+    <ul>
+      {% for key, value in dict %}
+        <li>{{ key }}: {{ value }}</li>
+      {% endfor %}
+    </ul>
+    
+It can also iterate over ranges, tuple elements, structs' and classes' stored properties (using ``Mirror``).
+
+You can iterate over range literals created using ``N...M`` syntax, both in ascending and descending order:
+
+.. 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
+
+    <ul>
+      {% for user in users where user.name != "Kyle" %}
+        <li>{{ user }}</li>
+      {% endfor %}
+    </ul>
+
 The ``for`` tag can take an optional ``{% empty %}`` block that will be
 displayed if the given list is empty or could not be found.
 
@@ -36,7 +69,26 @@ The for block sets a few variables available within the loop:
 
 - ``first`` - True if this is the first time through the loop
 - ``last`` - True if this is the last time through the loop
-- ``counter`` - The current iteration of 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:
+
+.. code-block:: html+django
+
+    {% for user in users %}
+      {% if forloop.first %}
+        This is the first user.
+      {% endif %}
+    {% endfor %}
+
+.. code-block:: html+django
+
+    {% for user in users %}
+      This is user number {{ forloop.counter }} user.
+    {% endfor %}
+
 
 ``if``
 ~~~~~~
@@ -52,10 +104,12 @@ true the contents of the block are processed. Being true is defined as:
 
 .. code-block:: html+django
 
-    {% if variable %}
-      The variable was found in the current context.
+    {% if admin %}
+      The user is an administrator.
+    {% elif user %}
+      A user is logged in.
     {% else %}
-      The variable was not found.
+      No user was found.
     {% endif %}
 
 Operators
@@ -83,7 +137,7 @@ 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
 
@@ -95,6 +149,19 @@ 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
 """""""""""""""
 
@@ -177,6 +244,26 @@ Will be treated as:
 ``now``
 ~~~~~~~
 
+``filter``
+~~~~~~~~~~
+
+Filters the contents of the block.
+
+.. code-block:: html+django
+
+    {% filter lowercase %}
+      This Text Will Be Lowercased.
+    {% endfilter %}
+
+You can chain multiple filters with a pipe (`|`).
+
+.. code-block:: html+django
+
+    {% filter lowercase|capitalize %}
+      This Text Will First Be Lowercased, Then The First Character Will BE
+      Capitalised.
+    {% endfilter %}
+
 ``include``
 ~~~~~~~~~~~
 
@@ -186,20 +273,37 @@ You can include another template using the `include` tag.
 
     {% include "comment.html" %}
 
-The `include` tag requires a FileSystemLoader to be found inside your context with the paths, or bundles used to lookup the template.
+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.
+
+.. 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
 
-    let context = Context(dictionary: [
-      "loader": FileSystemLoader(bundle: [NSBundle.mainBundle()])
-    ])
+    let environment = Environment(bundle: [Bundle.main])
+    let template = environment.loadTemplate(name: "index.html")
 
 ``extends``
 ~~~~~~~~~~~
 
+Extends the template from a parent template.
+
+.. code-block:: html+django
+
+    {% extends "base.html" %}
+
+See :ref:`template-inheritance` for more information.
+
 ``block``
 ~~~~~~~~~
 
+Defines a block that can be overridden by child templates. See
+:ref:`template-inheritance` for more information.
+
 .. _built-in-filters:
 
 Built-in Filters
@@ -209,7 +313,7 @@ Built-in Filters
 ~~~~~~~~~~~~~~
 
 The capitalize filter allows you to capitalize a string.
-For example, `stencil` to `Stencil`.
+For example, `stencil` to `Stencil`. Can be applied to array of strings to change each string.
 
 .. code-block:: html+django
 
@@ -219,7 +323,7 @@ For example, `stencil` to `Stencil`.
 ~~~~~~~~~~~~~
 
 The uppercase filter allows you to transform a string to uppercase.
-For example, `Stencil` to `STENCIL`.
+For example, `Stencil` to `STENCIL`. Can be applied to array of strings to change each string.
 
 .. code-block:: html+django
 
@@ -229,7 +333,7 @@ For example, `Stencil` to `STENCIL`.
 ~~~~~~~~~~~~~
 
 The uppercase filter allows you to transform a string to lowercase.
-For example, `Stencil` to `stencil`.
+For example, `Stencil` to `stencil`. Can be applied to array of strings to change each string.
 
 .. code-block:: html+django
 
@@ -248,10 +352,47 @@ value of the variable. For example:
 ``join``
 ~~~~~~~~
 
-Join an array with a string.
+Join an array of items.
 
 .. code-block:: html+django
 
     {{ value|join:", " }}
 
-.. note:: The value MUST be an array of Strngs and the separator must be a string.
+.. 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

@@ -58,9 +58,9 @@ author = 'Kyle Fuller'
 # built documents.
 #
 # The short X.Y version.
-version = '0.7.0'
+version = '0.14.2'
 # The full version, including alpha/beta/rc tags.
-release = '0.7.0'
+release = '0.14.2'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.

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

@@ -3,13 +3,15 @@ Custom Template Tags and Filters
 
 You can build your own custom filters and tags and pass them down while
 rendering your template. Any custom filters or tags must be registered with a
-namespace which contains all filters and tags available to the template.
+extension which contains all filters and tags available to the template.
 
 .. code-block:: swift
 
-    let namespace = Namespace()
-    // Register your filters and tags with the namespace
-    let rendered = try template.render(context, namespace: namespace)
+    let ext = Extension()
+    // Register your filters and tags with the extension
+
+    let environment = Environment(extensions: [ext])
+    try environment.renderTemplate(name: "example.html")
 
 Custom Filters
 --------------
@@ -18,7 +20,7 @@ Registering custom filters:
 
 .. code-block:: swift
 
-    namespace.registerFilter("double") { (value: Any?) in
+    ext.registerFilter("double") { (value: Any?) in
       if let value = value as? Int {
         return value * 2
       }
@@ -30,7 +32,7 @@ Registering custom filters with arguments:
 
 .. code-block:: swift
 
-    namespace.registerFilter("multiply") { (value: Any?, arguments: [Any?]) in
+    ext.registerFilter("multiply") { (value: Any?, arguments: [Any?]) in
       let amount: Int
 
       if let value = arguments.first as? Int {
@@ -40,12 +42,23 @@ Registering custom filters with arguments:
       }
 
       if let value = value as? Int {
-        return value * 2
+        return value * amount
       }
 
       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
 -----------
 
@@ -54,7 +67,7 @@ write your own custom tags. The following is the simplest form:
 
 .. code-block:: swift
 
-    namespace.registerSimpleTag("custom") { context in
+    ext.registerSimpleTag("custom") { context in
       return "Hello World"
     }
 

docs/getting-started.rst

@@ -0,0 +1,37 @@
+Getting Started
+===============
+
+The easiest way to render a template using Stencil is to create a template and
+call render on it providing a context.
+
+.. code-block:: swift
+
+    let template = Template(templateString: "Hello {{ name }}")
+    try template.render(["name": "kyle"])
+
+For more advanced uses, you would normally create an ``Environment`` and call
+the ``renderTemplate`` convinience method.
+
+.. code-block:: swift
+
+    let environment = Environment()
+
+    let context = ["name": "kyle"]
+    try environment.renderTemplate(string: "Hello {{ name }}", context: context)
+
+Template Loaders
+----------------
+
+A template loader allows you to load files from disk or elsewhere. Using a
+``FileSystemLoader`` we can easily render a template from disk.
+
+For example, to render a template called ``index.html`` inside the
+``templates/`` directory we can use the following:
+
+.. code-block:: swift
+
+    let fsLoader = FileSystemLoader(paths: ["templates/"])
+    let environment = Environment(loader: fsLoader)
+
+    let context = ["name": "kyle"]
+    try environment.renderTemplate(name: "index.html", context: context)

docs/index.rst

@@ -17,32 +17,48 @@ feel right at home with Stencil.
 
 .. code-block:: swift
 
-   struct Article {
-     let title: String
-     let author: String
-   }
+    import Stencil
 
-    let context = Context(dictionary: [
+    struct Article {
+      let title: String
+      let author: String
+    }
+
+    let context = [
       "articles": [
         Article(title: "Migrating from OCUnit to XCTest", author: "Kyle Fuller"),
         Article(title: "Memory Management with ARC", author: "Kyle Fuller"),
       ]
-    ])
+    ]
 
-    do {
-      let template = try Template(named: "template.html")
-      let rendered = try template.render(context)
-      print(rendered)
-    } catch {
-      print("Failed to render template \(error)")
-    }
+    let environment = Environment(loader: FileSystemLoader(paths: ["templates/"])
+    let rendered = try environment.renderTemplate(name: "articles.html", context: context)
 
-Contents:
+    print(rendered)
+
+The User Guide
+--------------
+
+For Template Writers
+~~~~~~~~~~~~~~~~~~~~
+
+Resources for Stencil template authors to write Stencil templates.
 
 .. toctree::
    :maxdepth: 2
 
    templates
    builtins
-   api/context
+
+For Developers
+~~~~~~~~~~~~~~
+
+Resources to help you integrate Stencil into a Swift project.
+
+.. toctree::
+   :maxdepth: 1
+
+   installation
+   getting-started
+   api
    custom-template-tags-and-filters

docs/installation.rst

@@ -0,0 +1,52 @@
+Installation
+============
+
+Swift Package Manager
+---------------------
+
+If you're using the Swift Package Manager, you can add ``Stencil`` to your
+dependencies inside ``Package.swift``.
+
+.. code-block:: swift
+
+    import PackageDescription
+
+    let package = Package(
+      name: "MyApplication",
+      dependencies: [
+        .Package(url: "https://github.com/stencilproject/Stencil.git", majorVersion: 0, minor: 13),
+      ]
+    )
+
+CocoaPods
+---------
+
+If you're using CocoaPods, you can add Stencil to your ``Podfile`` and then run
+``pod install``.
+
+.. code-block:: ruby
+
+    pod 'Stencil', '~> 0.14.2'
+
+Carthage
+--------
+
+.. note:: Use at your own risk. We don't offer support for Carthage and instead recommend you use Swift Package Manager.
+
+1) Add ``Stencil`` to your ``Cartfile``:
+
+    .. code-block:: text
+
+        github "stencilproject/Stencil" ~> 0.14.2
+
+2) Checkout your dependencies, generate the Stencil Xcode project, and then use Carthage to build Stencil:
+
+    .. code-block:: shell
+
+        $ carthage update
+        $ (cd Carthage/Checkouts/Stencil && swift package generate-xcodeproj)
+        $ carthage build
+
+3) Follow the Carthage steps to add the built frameworks to your project.
+
+To learn more about this approach see `Using Swift Package Manager with Carthage <https://fuller.li/posts/using-swift-package-manager-with-carthage/>`_.

docs/templates.rst

@@ -1,5 +1,5 @@
-Templates
-=========
+Language overview
+==================
 
 - ``{{ ... }}`` for variables to print to the template output
 - ``{% ... %}`` for tags
@@ -20,9 +20,9 @@ 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
+- Type introspection (via ``Mirror``)
 
 For example, if `people` was an array:
 
@@ -31,6 +31,24 @@ 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.
+
 Filters
 ~~~~~~~
 
@@ -75,3 +93,93 @@ To comment out part of your template, you can use the following syntax:
 .. code-block:: html+django
 
     {# My comment is completely hidden #}
+
+.. _template-inheritance:
+
+Template inheritance
+--------------------
+
+Template inheritance allows the common components surrounding individual pages
+to be shared across other templates. You can define blocks which can be
+overidden in any child template.
+
+Let's take a look at an example. Here is our base template (``base.html``):
+
+.. code-block:: html+django
+
+    <html>
+      <head>
+        <title>{% block title %}Example{% endblock %}</title>
+      </head>
+
+      <body>
+        <aside>
+          {% block sidebar %}
+            <ul>
+              <li><a href="/">Home</a></li>
+              <li><a href="/notes/">Notes</a></li>
+            </ul>
+          {% endblock %}
+        </aside>
+
+        <section>
+          {% block content %}{% endblock %}
+        </section>
+      </body>
+    </html>
+
+This example declares three blocks, ``title``, ``sidebar`` and ``content``. We
+can use the ``{% extends %}`` template tag to inherit from out base template
+and then use ``{% block %}`` to override any blocks from our base template.
+
+A child template might look like the following:
+
+.. code-block:: html+django
+
+    {% extends "base.html" %}
+
+    {% block title %}Notes{% endblock %}
+
+    {% block content %}
+      {% for note in notes %}
+        <h2>{{ note }}</h2>
+      {% endfor %}
+    {% endblock %}
+
+.. note:: You can use ``{{ block.super }}` inside a block to render the contents of the parent block inline.
+
+Since our child template doesn't declare a sidebar block. The original sidebar
+from our base template will be used. Depending on the content of ``notes`` our
+template might be rendered like the following:
+
+.. code-block:: html
+
+    <html>
+      <head>
+        <title>Notes</title>
+      </head>
+
+      <body>
+        <aside>
+          <ul>
+            <li><a href="/">Home</a></li>
+            <li><a href="/notes/">Notes</a></li>
+          </ul>
+        </aside>
+
+        <section>
+          <h2>Pick up food</h2>
+          <h2>Do laundry</h2>
+        </section>
+      </body>
+    </html>
+
+You can use as many levels of inheritance as needed. One common way of using
+inheritance is the following three-level approach:
+
+* Create a ``base.html`` template that holds the main look-and-feel of your site.
+* Create a ``base_SECTIONNAME.html`` template for each “section” of your site.
+  For example, ``base_news.html``, ``base_news.html``. These templates all
+  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.

rakelib/changelog.rake

@@ -0,0 +1,34 @@
+NEW_CHANGELOG_SECTION = "## Master\n" + ['Breaking', 'Enhancements', 'Deprecations', 'Bug Fixes', 'Internal Changes'].map do |s|
+  <<~MARKDOWN
+
+    ### #{s}
+    
+    _None_
+  MARKDOWN
+end.join
+
+def changelog_first_section
+  content = []
+  section_count = 0
+  File.foreach(CHANGELOG_FILE) do |line|
+    section_count += 1 if line.start_with?('## ')
+    break if section_count > 1
+    content.append(line) if section_count == 1
+  end
+  content[1..].join
+end
+
+namespace :changelog do
+  # rake changelog:reset
+  desc "Add a new empty section at the top of the changelog and git push it"
+  task :reset do
+    header "Reset CHANGELOG"
+    content = File.read(CHANGELOG_FILE)
+    new_content = NEW_CHANGELOG_SECTION + "\n" + content
+    File.write(CHANGELOG_FILE, new_content)
+
+    sh("git", "add", CHANGELOG_FILE)
+    sh("git", "commit", "-m", "Reset CHANGELOG")
+    sh("git", "push")
+  end
+end

rakelib/github.rake

@@ -0,0 +1,52 @@
+require 'octokit'
+
+def repo_slug
+  url_parts = `git remote get-url origin`.chomp.split(%r{/|:})
+  last_two_parts = url_parts[-2..-1].join('/')
+  last_two_parts.gsub(/\.git$/, '')
+end
+
+def github_client
+  Octokit::Client.new(:netrc => true)
+end
+
+namespace :github do
+  # rake github:create_release_pr[version]
+  task :create_release_pr, [:version] do |_, args|
+    version = args[:version]
+    branch = release_branch(version)
+
+    title = "Release #{version}"
+    body = <<~BODY
+      This PR prepares the release for version #{version}.
+  
+      Once the PR is merged into master, run `bundle exec rake release:finish` to tag and push to trunk.
+    BODY
+
+    header "Opening PR"
+    res = github_client.create_pull_request(repo_slug, "master", branch, title, body)
+    info "Pull request created: #{res['html_url']}"
+  end
+
+  # rake github:tag
+  task :tag do
+    tag = current_pod_version
+    sh("git", "tag", tag)
+    sh("git", "push", "origin", tag)
+  end
+
+  # rake github:create_release
+  task :create_release do
+    tag_name = current_pod_version
+    title = tag_name
+    body = changelog_first_section()
+    res = github_client.create_release(repo_slug, tag_name, name: title, body: body)
+    info "GitHub Release created: #{res['html_url']}"
+  end
+
+  # rake github:pull_master
+  task :pull_master do
+    sh("git", "switch", "master")
+    sh("git", "pull")
+  end
+end

rakelib/pod.rake

@@ -0,0 +1,21 @@
+require 'json'
+
+def current_pod_version
+  JSON.parse(File.read(PODSPEC_FILE))['version']
+end
+
+namespace :pod do
+  # rake pod:lint
+  desc "Lint the podspec"
+  task :lint do
+    header "Linting podspec"
+    sh("pod", "lib", "lint", PODSPEC_FILE)
+  end
+
+  # rake pod:push
+  desc "Push the podspec to trunk"
+  task :push do
+    header "Pushing podspec to trunk"
+    sh("pod", "trunk", "push", PODSPEC_FILE)
+  end
+end

rakelib/release.rake

@@ -0,0 +1,67 @@
+require 'json'
+
+namespace :release do
+
+  # rake release:new
+  desc "Ask for a version number and prepare a release PR for that version"
+  task :new do
+    info "Current version is: #{current_pod_version}"
+    print "What version do you want to release? "
+    new_version = STDIN.gets.chomp
+
+    Rake::Task['release:start'].invoke(new_version)
+  end
+
+  # rake release:start[version]
+  desc "Start a release by creating a PR with the required changes to bump the version"
+  task :start, [:version] => ['release:create_branch', 'release:update_files', 'pod:lint', 'release:push_branch', 'github:create_release_pr', 'github:pull_master']
+
+  # rake release:finish[version]
+  desc "Finish a release after the PR has been merged, by tagging master and pushing to trunk"
+  task :finish => ['github:pull_master', 'github:tag', 'pod:push', 'github:create_release', 'changelog:reset']
+
+
+  ### Helper tasks ###
+
+  # rake release:create_branch[version]
+  task :create_branch, [:version] do |_, args|
+    branch = release_branch(args[:version])
+
+    header "Creating release branch"
+    sh("git", "checkout", "-b", branch)
+  end
+
+  # rake release:update_files[version]
+  task :update_files, [:version] do |_, args|
+    version = args[:version]
+
+    header "Updating files for version #{version}"
+
+    podspec = JSON.parse(File.read(PODSPEC_FILE))
+    podspec['version'] = version
+    podspec['source']['tag'] = version
+    File.write(PODSPEC_FILE, JSON.pretty_generate(podspec) + "\n")
+
+    replace(CHANGELOG_FILE, '## Master' => "\#\# #{version}")
+    replace("docs/conf.py",
+      /^version = .*/ => %Q(version = '#{version}'),
+      /^release = .*/ => %Q(release = '#{version}')
+    )
+    replace("docs/installation.rst",
+      /pod 'Stencil', '.*'/ => %Q(pod 'Stencil', '~> #{version}'),
+      /github "stencilproject\/Stencil" ~> .*/ => %Q(github "stencilproject/Stencil" ~> #{version})
+    )
+
+    ## Commit Changes
+    sh("git", "add", PODSPEC_FILE, CHANGELOG_FILE, "docs/*")
+    sh("git", "commit", "-m", "Version #{version}")
+  end
+
+  # rake release:push_branch[version]
+  task :push_branch, [:version] do |_, args|
+    branch = release_branch(args[:version])
+
+    header "Pushing #{branch} to origin"
+    sh("git", "push", "-u", "origin", branch)
+  end
+end

rakelib/utils.rake

@@ -0,0 +1,28 @@
+def colorize(string, *codes)
+  if `tput colors`.chomp.to_i >= 8
+    code = codes.join(';')
+    puts "\e[#{code}m" + string + "\e[0m"
+  else
+    puts string
+  end
+end
+
+def header(title)
+  puts colorize("==> #{title}...", 1, 32) # bold, green
+end
+
+def info(string)
+  puts colorize(string, 34) # blue
+end
+
+def release_branch(version)
+  "release/#{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