Support @each

lib/src/ast/sass.dart

@@ -28,6 +28,7 @@ export 'sass/statement/comment.dart';
 export 'sass/statement/content_rule.dart';
 export 'sass/statement/debug_rule.dart';
 export 'sass/statement/declaration.dart';
+export 'sass/statement/each_rule.dart';
 export 'sass/statement/error_rule.dart';
 export 'sass/statement/extend_rule.dart';
 export 'sass/statement/for_rule.dart';

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

@@ -0,0 +1,31 @@
+// 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/statement.dart';
+import '../expression.dart';
+import '../statement.dart';
+
+class EachRule implements Statement {
+  final List<String> variables;
+
+  final Expression list;
+
+  final List<Statement> children;
+
+  final FileSpan span;
+
+  EachRule(Iterable<String> variables, this.list, Iterable<Statement> children,
+      this.span)
+      : variables = new List.unmodifiable(variables),
+        children = new List.unmodifiable(children);
+
+  /*=T*/ accept/*<T>*/(StatementVisitor/*<T>*/ visitor) =>
+      visitor.visitEachRule(this);
+
+  String toString() =>
+      "@each ${variables.map((variable) => '\$' + variable).join(', ')} in "
+      "$list {${children.join(" ")}}";
+}

lib/src/parser.dart

@@ -327,6 +327,8 @@ class Parser {
         return _contentRule(start);
       case "debug":
         return _debugRule(start);
+      case "each":
+        return _eachRule(start, child);
       case "error":
         return _errorRule(start);
       case "extend":
@@ -367,6 +369,8 @@ class Parser {
         return _contentRule(start);
       case "debug":
         return _debugRule(start);
+      case "each":
+        return _eachRule(start, _declarationChild);
       case "error":
         return _errorRule(start);
       case "for":
@@ -389,6 +393,8 @@ class Parser {
     switch (_atRuleName()) {
       case "debug":
         return _debugRule(start);
+      case "each":
+        return _eachRule(start, _functionAtRule);
       case "error":
         return _errorRule(start);
       case "for":
@@ -436,6 +442,28 @@ class Parser {
   DebugRule _debugRule(LineScannerState start) =>
       new DebugRule(_expression(), _scanner.spanFrom(start));
 
+  EachRule _eachRule(LineScannerState start, Statement child()) {
+    var wasInControlDirective = _inControlDirective;
+    _inControlDirective = true;
+
+    var variables = [_variableName()];
+    _ignoreComments();
+    while (_scanner.scanChar($comma)) {
+      _ignoreComments();
+      variables.add(_variableName());
+      _ignoreComments();
+    }
+
+    _scanner.expect("in");
+    _ignoreComments();
+
+    var list = _expression();
+    var children = _children(child);
+    _inControlDirective = wasInControlDirective;
+
+    return new EachRule(variables, list, children, _scanner.spanFrom(start));
+  }
+
   ErrorRule _errorRule(LineScannerState start) =>
       new ErrorRule(_expression(), _scanner.spanFrom(start));
 
@@ -1938,6 +1966,7 @@ class Parser {
   /// [the CSS algorithm]: https://drafts.csswg.org/css-syntax-3/#would-start-an-identifier
   bool _lookingAtInterpolatedIdentifier() {
     var first = _scanner.peekChar();
+    if (first == null) return false;
     if (isNameStart(first) || first == $backslash) return true;
     if (first == $hash) return _scanner.peekChar(1) == $lbrace;
 

lib/src/value.dart

@@ -24,12 +24,12 @@ abstract class Value {
 
   int get asInt => throw new InternalException("$this is not an int.");
 
+  List<Value> get asList => [this];
+
   const Value();
 
   /*=T*/ accept/*<T>*/(ValueVisitor/*<T>*/ visitor);
 
-  List<Value> asList() => [this];
-
   Value unaryPlus() => new SassIdentifier("+${valueToCss(this)}");
 
   Value unaryMinus() => new SassIdentifier("-${valueToCss(this)}");

lib/src/value/list.dart

@@ -15,6 +15,8 @@ class SassList extends Value {
 
   bool get isBlank => contents.every((element) => element.isBlank);
 
+  List<Value> get asList => contents;
+
   SassList(Iterable<Value> contents, this.separator, {bool bracketed: false})
       : contents = new List.unmodifiable(contents),
         isBracketed = bracketed;

lib/src/value/map.dart

@@ -10,6 +10,14 @@ import '../value.dart';
 class SassMap extends Value {
   final Map<Value, Value> contents;
 
+  List<SassList> get asList {
+    var result = <SassList>[];
+    contents.forEach((key, value) {
+      result.add(new SassList([key, value], ListSeparator.space));
+    });
+    return result;
+  }
+
   SassMap(Map<Value, Value> contents)
       : contents = new Map.unmodifiable(contents);
 

lib/src/visitor/interface/statement.dart

@@ -11,6 +11,7 @@ abstract class StatementVisitor<T> {
   T visitContentRule(ContentRule node);
   T visitDebugRule(DebugRule node);
   T visitDeclaration(Declaration node);
+  T visitEachRule(EachRule node);
   T visitErrorRule(ErrorRule node);
   T visitExtendRule(ExtendRule node);
   T visitForRule(ForRule node);

lib/src/visitor/perform.dart

@@ -211,6 +211,33 @@ class PerformVisitor implements StatementVisitor, ExpressionVisitor<Value> {
     }
   }
 
+  void visitEachRule(EachRule node) {
+    var list = node.list.accept(this);
+    var setVariables = node.variables.length == 1
+        ? (value) => _environment.setLocalVariable(node.variables.first, value)
+        : (value) => _setMultipleVariables(node.variables, value);
+    _environment.scope(() {
+      for (var element in list.asList) {
+        setVariables(element);
+        for (var child in node.children) {
+          child.accept(this);
+        }
+      }
+    }, semiGlobal: true);
+  }
+
+  void _setMultipleVariables(List<String> variables, Value value) {
+    var list = value.asList;
+    var minLength = math.min(variables.length, list.length);
+    for (var i = 0; i < minLength; i++) {
+      _environment.setLocalVariable(variables[i], list[i]);
+    }
+    for (var i = minLength; i < variables.length; i++) {
+      // TODO: Sass null
+      _environment.setLocalVariable(variables[i], null);
+    }
+  }
+
   void visitErrorRule(ErrorRule node) {
     throw _exception(node.expression.accept(this).toString(), node.span);
   }
@@ -720,7 +747,7 @@ class PerformVisitor implements StatementVisitor, ExpressionVisitor<Value> {
     if (rest is SassMap) {
       _addRestMap(named, rest, invocation.span);
     } else if (rest is SassList) {
-      positional.addAll(rest.asList());
+      positional.addAll(rest.asList);
     } else {
       positional.add(rest);
     }