Support keyframes.

lib/src/ast/css.dart

@@ -6,6 +6,7 @@ export 'css/at_rule.dart';
 export 'css/comment.dart';
 export 'css/declaration.dart';
 export 'css/import.dart';
+export 'css/keyframe_block.dart';
 export 'css/media_query.dart';
 export 'css/media_rule.dart';
 export 'css/node.dart';

lib/src/ast/css/keyframe_block.dart

@@ -0,0 +1,27 @@
+// Copyright 2016 Google Inc. Use of this source code is governed by an
+// MIT-style license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import 'package:source_span/source_span.dart';
+
+import '../../visitor/interface/css.dart';
+import 'node.dart';
+import 'value.dart';
+
+/// A block within a `@keyframes` rule.
+///
+/// For example, `10% {opacity: 0.5}`.
+class CssKeyframeBlock extends CssParentNode {
+  /// The selector for this block.
+  final CssValue<List<String>> selector;
+
+  final FileSpan span;
+
+  CssKeyframeBlock(this.selector, this.span);
+
+  /*=T*/ accept/*<T>*/(CssVisitor/*<T>*/ visitor) =>
+      visitor.visitKeyframeBlock(this);
+
+  CssKeyframeBlock copyWithoutChildren() =>
+      new CssKeyframeBlock(selector, span);
+}

lib/src/ast/sass/at_root_query.dart

@@ -30,7 +30,7 @@ class AtRootQuery {
   /// Whether this excludes `@media` rules.
   ///
   /// Note that this takes [include] into account.
-  bool get excludesMedia => _all ? !include : _excludesName("media");
+  bool get excludesMedia => _all ? !include : excludesName("media");
 
   /// Whether this excludes style rules.
   ///
@@ -61,11 +61,11 @@ class AtRootQuery {
   bool excludes(CssParentNode node) {
     if (_all) return !include;
     if (_rule && node is CssStyleRule) return !include;
-    return _excludesName(_nameFor(node));
+    return excludesName(_nameFor(node));
   }
 
   /// Returns whether [this] excludes a node with the given [name].
-  bool _excludesName(String name) => names.contains(name) != include;
+  bool excludesName(String name) => names.contains(name) != include;
 
   /// Returns the at-rule name for [node], or `null` if it's not an at-rule.
   String _nameFor(CssParentNode node) {

lib/src/ast/sass/statement/at_rule.dart

@@ -4,6 +4,7 @@
 
 import 'package:source_span/source_span.dart';
 
+import '../../../utils.dart';
 import '../../../visitor/interface/statement.dart';
 import '../interpolation.dart';
 import '../statement.dart';
@@ -13,6 +14,9 @@ class AtRule implements Statement {
   /// The name of this rule.
   final String name;
 
+  /// Like [name], but without any vendor prefixes.
+  final String normalizedName;
+
   /// The value of this rule.
   final Interpolation value;
 
@@ -24,8 +28,10 @@ class AtRule implements Statement {
 
   final FileSpan span;
 
-  AtRule(this.name, this.span, {this.value, Iterable<Statement> children})
-      : children = children == null ? null : new List.unmodifiable(children);
+  AtRule(String name, this.span, {this.value, Iterable<Statement> children})
+      : name = name,
+        normalizedName = unvendor(name),
+        children = children == null ? null : new List.unmodifiable(children);
 
   /*=T*/ accept/*<T>*/(StatementVisitor/*<T>*/ visitor) =>
       visitor.visitAtRule(this);

lib/src/parse/at_root_query.dart

@@ -16,7 +16,7 @@ class AtRootQueryParser extends Parser {
       scanner.expectChar($lparen);
       whitespace();
       var include = scanIdentifier("with");
-      if (!include) expectIdentifier("without");
+      if (!include) expectIdentifier("without", name: '"with" or "without"');
       whitespace();
       scanner.expectChar($colon);
       whitespace();

lib/src/parse/keyframe_selector.dart

@@ -0,0 +1,73 @@
+// Copyright 2016 Google Inc. Use of this source code is governed by an
+// MIT-style license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import 'package:charcode/charcode.dart';
+
+import '../util/character.dart';
+import 'parser.dart';
+
+/// A parser for `@keyframes` block selectors.
+class KeyframeSelectorParser extends Parser {
+  KeyframeSelectorParser(String contents, {url}) : super(contents, url: url);
+
+  List<String> parse() {
+    return wrapSpanFormatException(() {
+      whitespace();
+
+      var selectors = <String>[];
+      do {
+        if (lookingAtIdentifier()) {
+          if (scanIdentifier("from")) {
+            selectors.add("from");
+          } else {
+            expectIdentifier("to", name: '"to" or "from"');
+            selectors.add("to");
+          }
+        } else {
+          selectors.add(_percentage());
+        }
+        whitespace();
+      } while (scanner.scanChar($comma));
+
+      return selectors;
+    });
+  }
+
+  String _percentage() {
+    var buffer = new StringBuffer();
+    if (scanner.scanChar($plus)) buffer.writeCharCode($plus);
+
+    var second = scanner.peekChar();
+    if (!isDigit(second) && second != $dot) {
+      scanner.error("Expected number.");
+    }
+
+    while (isDigit(scanner.peekChar())) {
+      buffer.writeCharCode(scanner.readChar());
+    }
+
+    if (scanner.peekChar() == $dot) {
+      buffer.writeCharCode(scanner.readChar());
+
+      while (isDigit(scanner.peekChar())) {
+        buffer.writeCharCode(scanner.readChar());
+      }
+    }
+
+    if (scanIdentifier("e", ignoreCase: true)) {
+      buffer.write(scanner.readChar());
+      var next = scanner.peekChar();
+      if (next == $plus || next == $minus) buffer.write(scanner.readChar());
+      if (!isDigit(scanner.peekChar())) scanner.error("Expected digit.");
+
+      while (isDigit(scanner.peekChar())) {
+        buffer.writeCharCode(scanner.readChar());
+      }
+    }
+
+    scanner.expectChar($percent);
+    buffer.writeCharCode($percent);
+    return buffer.toString();
+  }
+}

lib/src/util/character.dart

@@ -28,7 +28,8 @@ bool isAlphabetic(int character) =>
     (character >= $A && character <= $Z);
 
 /// Returns whether [character] is a number.
-bool isDigit(int character) => character >= $0 && character <= $9;
+bool isDigit(int character) =>
+    character != null && character >= $0 && character <= $9;
 
 /// Returns whether [character] is legal as the start of a Sass identifier.
 bool isNameStart(int character) =>

lib/src/visitor/interface/css.dart

@@ -12,6 +12,7 @@ abstract class CssVisitor<T> {
   T visitComment(CssComment node);
   T visitDeclaration(CssDeclaration node);
   T visitImport(CssImport node);
+  T visitKeyframeBlock(CssKeyframeBlock node);
   T visitMediaRule(CssMediaRule node);
   T visitStyleRule(CssStyleRule node);
   T visitStylesheet(CssStylesheet node);

lib/src/visitor/perform.dart

@@ -17,6 +17,7 @@ import '../environment.dart';
 import '../exception.dart';
 import '../extend/extender.dart';
 import '../io.dart';
+import '../parse/keyframe_selector.dart';
 import '../utils.dart';
 import '../value.dart';
 import 'interface/statement.dart';
@@ -82,6 +83,9 @@ class _PerformVisitor
   /// Whether we're currently building the output of an unknown at rule.
   var _inUnknownAtRule = false;
 
+  /// Whether we're currently building the output of a `@keyframes` rule.
+  var _inKeyframes = false;
+
   /// The resolved URLs for each [ImportRule] that's been seen so far.
   ///
   /// This is cached in case the same file is imported multiple times, and thus
@@ -228,14 +232,24 @@ class _PerformVisitor
       var innerScope = scope;
       scope = (callback) => _withMediaQueries(null, () => innerScope(callback));
     }
+
+    if (_inKeyframes && query.excludesName('keyframes')) {
+      var innerScope = scope;
+      scope = (callback) {
+        var wasInKeyframes = _inKeyframes;
+        _inKeyframes = false;
+        innerScope(callback);
+        _inKeyframes = wasInKeyframes;
+      };
+    }
+
     if (_inUnknownAtRule && !included.any((parent) => parent is CssAtRule)) {
       var innerScope = scope;
       scope = (callback) {
         var wasInUnknownAtRule = _inUnknownAtRule;
         _inUnknownAtRule = false;
-        var result = innerScope(callback);
+        innerScope(callback);
         _inUnknownAtRule = wasInUnknownAtRule;
-        return result;
       };
     }
 
@@ -270,7 +284,7 @@ class _PerformVisitor
   }
 
   Value visitDeclaration(Declaration node) {
-    if (_selector == null && !_inUnknownAtRule) {
+    if (_selector == null && !_inUnknownAtRule && !_inKeyframes) {
       throw _exception(
           "Declarations may only be used within style rules.", node.span);
     }
@@ -357,8 +371,6 @@ class _PerformVisitor
           "At-rules may not be used within nested declarations.", node.span);
     }
 
-    var wasInUnknownAtRule = _inUnknownAtRule;
-    _inUnknownAtRule = true;
     var value = node.value == null
         ? null
         : _interpolationToValue(node.value, trim: true);
@@ -369,6 +381,14 @@ class _PerformVisitor
       return null;
     }
 
+    var wasInKeyframes = _inKeyframes;
+    var wasInUnknownAtRule = _inUnknownAtRule;
+    if (node.normalizedName == 'keyframes') {
+      _inKeyframes = true;
+    } else {
+      _inUnknownAtRule = true;
+    }
+
     _withParent(new CssAtRule(node.name, node.span, value: value), () {
       if (_selector == null) {
         for (var child in node.children) {
@@ -388,6 +408,7 @@ class _PerformVisitor
     }, through: (node) => node is CssStyleRule);
 
     _inUnknownAtRule = wasInUnknownAtRule;
+    _inKeyframes = wasInKeyframes;
     return null;
   }
 
@@ -601,6 +622,21 @@ class _PerformVisitor
     }
 
     var selectorText = _interpolationToValue(node.selector, trim: true);
+    if (_inKeyframes) {
+      var parsedSelector = _adjustParseError(node.selector.span,
+          () => new KeyframeSelectorParser(selectorText.value).parse());
+      var rule = new CssKeyframeBlock(
+          new CssValue(
+              new List.unmodifiable(parsedSelector), node.selector.span),
+          node.span);
+      _withParent(rule, () {
+        for (var child in node.children) {
+          child.accept(this);
+        }
+      }, through: (node) => node is CssStyleRule);
+      return null;
+    }
+
     var parsedSelector = _adjustParseError(
         node.selector.span, () => new SelectorList.parse(selectorText.value));
     parsedSelector = _addExceptionSpan(node.selector.span,

lib/src/visitor/serialize.dart

@@ -144,6 +144,13 @@ class _SerializeCssVisitor
     _buffer.writeCharCode($semicolon);
   }
 
+  void visitKeyframeBlock(CssKeyframeBlock node) {
+    _writeIndentation();
+    _writeBetween(node.selector.value, ", ", _buffer.write);
+    _buffer.writeCharCode($space);
+    _visitChildren(node.children);
+  }
+
   void visitMediaQuery(CssMediaQuery query) {
     if (query.modifier != null) {
       _buffer.write(query.modifier.value);