Support for @mixin, @include and @extend

pkg/csslib/lib/src/tree_printer.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of csslib.visitor;
 
 // TODO(terry): Enable class for debug only; when conditional imports enabled.
 
 /** Helper function to dump the CSS AST. */
 String treeToDebugString(styleSheet, [bool useSpan = false]) {
@@ skipping 123 matching lines @@
   void visitNamespaceDirective(NamespaceDirective node) {
     heading('NamespaceDirective', node);
     output.depth++;
     output.writeValue('prefix', node._prefix);
     output.writeValue('uri', node._uri);
     output.depth--;
   }
 
   void visitVarDefinitionDirective(VarDefinitionDirective node) {
     heading('Less variable definition', node);
+    output.depth++;
     visitVarDefinition(node.def);
+    output.depth--;
+  }
+
+  void visitMixinRulesetDirective(MixinRulesetDirective node) {
+    heading('Mixin top-level ${node.name}', node);
+    output.depth++;
+    _visitNodeList(node.rulesets);
+    output.depth--;
+  }
+
+  void visitMixinDeclarationDirective(MixinDeclarationDirective node) {
+    heading('Mixin declaration ${node.name}', node);
+    output.depth++;
+    visitDeclarationGroup(node.declarations);
+    output.depth--;
+  }
+
+  /**
+   * Added optional newLine for handling @include at top-level vs/ inside of
+   * a declaration group.
+   */
+  void visitIncludeDirective(IncludeDirective node) {
+    heading('IncludeDirective ${node.name}', node);
+  }
+
+  void visitIncludeMixinAtDeclaration(IncludeMixinAtDeclaration node) {
+    heading('IncludeMixinAtDeclaration ${node.include.name}', node);
+    output.depth++;
+    visitIncludeDirective(node.include);
+    output.depth--;
   }
 
   void visitRuleSet(RuleSet node) {
     heading('Ruleset', node);
     output.depth++;
     super.visitRuleSet(node);
     output.depth--;
   }
 
   void visitDeclarationGroup(DeclarationGroup node) {
@@ skipping 348 matching lines @@
   }
 
   void visitPaddingExpression(PaddingExpression node) {
     heading('Dart Style PaddingExpression', node);
   }
 
   void visitWidthExpression(WidthExpression node) {
     heading('Dart Style WidthExpression', node);
   }
 }