Implement trim whitespace

Tests/StencilTests/TrimBehaviourSpec.swift

@@ -0,0 +1,137 @@
+import Spectre
+import Stencil
+import XCTest
+
+final class TrimBehaviourTests: XCTestCase {
+  func testSmartTrimCanRemoveNewlines() throws {
+    let templateString = """
+      {% for item in items %}
+        - {{item}}
+      {% endfor %}
+      text
+      """
+
+    let context = ["items": ["item 1", "item 2"]]
+    let template = Template(templateString: templateString, environment: .init(trimBehaviour: .smart))
+    let result = try template.render(context)
+
+    // swiftlint:disable indentation_width
+    try expect(result) == """
+        - item 1
+        - item 2
+      text
+      """
+    // swiftlint:enable indentation_width
+  }
+
+  func testSmartTrimOnlyRemoveSingleNewlines() throws {
+    let templateString = """
+      {% for item in items %}
+
+        - {{item}}
+      {% endfor %}
+      text
+      """
+
+    let context = ["items": ["item 1", "item 2"]]
+    let template = Template(templateString: templateString, environment: .init(trimBehaviour: .smart))
+    let result = try template.render(context)
+
+    // swiftlint:disable indentation_width
+    try expect(result) == """
+
+        - item 1
+
+        - item 2
+      text
+      """
+    // swiftlint:enable indentation_width
+  }
+
+  func testSmartTrimCanRemoveNewlinesWhileKeepingWhitespace() throws {
+    // swiftlint:disable indentation_width
+    let templateString = """
+          Items:
+          {% for item in items %}
+              - {{item}}
+          {% endfor %}
+      """
+    // swiftlint:enable indentation_width
+
+    let context = ["items": ["item 1", "item 2"]]
+    let template = Template(templateString: templateString, environment: .init(trimBehaviour: .smart))
+    let result = try template.render(context)
+
+    // swiftlint:disable indentation_width
+    try expect(result) == """
+          Items:
+              - item 1
+              - item 2
+
+      """
+    // swiftlint:enable indentation_width
+  }
+
+  func testTrimSymbols() {
+    it("Respects whitespace control symbols in for tags") {
+      // swiftlint:disable indentation_width
+      let template: Template = """
+        {% for num in numbers -%}
+            {{num}}
+        {%- endfor %}
+        """
+      // swiftlint:enable indentation_width
+      let result = try template.render([ "numbers": Array(1...9) ])
+      try expect(result) == "123456789"
+    }
+    it("Respects whitespace control symbols in if tags") {
+      let template: Template = """
+        {% if value -%}
+          {{text}}
+        {%- endif %}
+        """
+      let result = try template.render([ "text": "hello", "value": true ])
+      try expect(result) == "hello"
+    }
+  }
+
+  func testTrimSymbolsOverridingEnvironment() {
+    let environment = Environment(trimBehaviour: .all)
+
+    it("respects whitespace control symbols in if tags") {
+      // swiftlint:disable indentation_width
+      let templateString = """
+          {% if value +%}
+          {{text}}
+        {%+ endif %}
+
+        """
+      // swiftlint:enable indentation_width
+      let template = Template(templateString: templateString, environment: environment)
+      let result = try template.render([ "text": "hello", "value": true ])
+      try expect(result) == "\n  hello\n"
+    }
+
+    it("can customize blocks on same line as text") {
+      // swiftlint:disable indentation_width
+      let templateString = """
+            Items:{% for item in items +%}
+                - {{item}}
+            {%- endfor %}
+        """
+      // swiftlint:enable indentation_width
+
+      let context = ["items": ["item 1", "item 2"]]
+      let template = Template(templateString: templateString, environment: environment)
+      let result = try template.render(context)
+
+      // swiftlint:disable indentation_width
+      try expect(result) == """
+            Items:
+                - item 1
+                - item 2
+        """
+      // swiftlint:enable indentation_width
+    }
+  }
+}