Support @while

lib/src/ast/sass.dart

@@ -44,6 +44,7 @@ export 'sass/statement/stylesheet.dart';
 export 'sass/statement/supports_rule.dart';
 export 'sass/statement/variable_declaration.dart';
 export 'sass/statement/warn_rule.dart';
+export 'sass/statement/while_rule.dart';
 export 'sass/supports_condition.dart';
 export 'sass/supports_condition/declaration.dart';
 export 'sass/supports_condition/interpolation.dart';

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

@@ -0,0 +1,25 @@
+// 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 WhileRule implements Statement {
+  final Expression condition;
+
+  final List<Statement> children;
+
+  final FileSpan span;
+
+  WhileRule(this.condition, Iterable<Statement> children, this.span)
+      : children = new List.unmodifiable(children);
+
+  /*=T*/ accept/*<T>*/(StatementVisitor/*<T>*/ visitor) =>
+      visitor.visitWhileRule(this);
+
+  String toString() => "@while $condition {${children.join(" ")}}";
+}

lib/src/parser.dart

@@ -351,6 +351,8 @@ class Parser {
         return _supportsRule(start);
       case "warn":
         return _warnRule(start);
+      case "while":
+        return _whileRule(start, child);
       default:
         return _unknownAtRule(start, name);
     }
@@ -375,6 +377,8 @@ class Parser {
         return _includeRule(start);
       case "warn":
         return _warnRule(start);
+      case "while":
+        return _whileRule(start, _declarationChild);
       default:
         return _disallowedAtRule(start);
     }
@@ -395,6 +399,8 @@ class Parser {
         return _returnRule(start);
       case "warn":
         return _warnRule(start);
+      case "while":
+        return _whileRule(start, _functionAtRule);
       default:
         return _disallowedAtRule(start);
     }
@@ -580,6 +586,15 @@ class Parser {
   WarnRule _warnRule(LineScannerState start) =>
       new WarnRule(_expression(), _scanner.spanFrom(start));
 
+  WhileRule _whileRule(LineScannerState start, Statement child()) {
+    var wasInControlDirective = _inControlDirective;
+    _inControlDirective = true;
+    var expression = _expression();
+    var children = _children(child);
+    _inControlDirective = wasInControlDirective;
+    return new WhileRule(expression, children, _scanner.spanFrom(start));
+  }
+
   AtRule _unknownAtRule(LineScannerState start, String name) {
     Interpolation value;
     var next = _scanner.peekChar();

lib/src/visitor/interface/statement.dart

@@ -27,4 +27,5 @@ abstract class StatementVisitor<T> {
   T visitSupportsRule(SupportsRule node);
   T visitVariableDeclaration(VariableDeclaration node);
   T visitWarnRule(WarnRule node);
+  T visitWhileRule(WhileRule node);
 }

lib/src/visitor/perform.dart

@@ -532,6 +532,16 @@ class PerformVisitor implements StatementVisitor, ExpressionVisitor<Value> {
     }
   }
 
+  void visitWhileRule(WhileRule node) {
+    _environment.scope(() {
+      while (node.condition.accept(this).isTruthy) {
+        for (var child in node.children) {
+          child.accept(this);
+        }
+      }
+    }, semiGlobal: true);
+  }
+
   // ## Expressions
 
   Value visitVariableExpression(VariableExpression node) {