Create and test source mapping for invocations.

pkg/compiler/lib/src/js/js_debug.dart

Index: pkg/compiler/lib/src/js/js_debug.dart
diff --git a/pkg/compiler/lib/src/js/js_debug.dart b/pkg/compiler/lib/src/js/js_debug.dart
new file mode 100644
index 0000000000000000000000000000000000000000..43ec1309d03b492d2feecec4ad84de60f69c2a74
--- /dev/null
+++ b/pkg/compiler/lib/src/js/js_debug.dart
@@ -0,0 +1,65 @@
+// Copyright (c) 2015, 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.
+
+/// Helper for debug JS nodes.
+
+library js.debug;
+
+import 'package:js_ast/js_ast.dart';
+import '../util/util.dart' show Indentation, Tagging;
+
+/// Unparse the JavaScript [node].
+String nodeToString(Node node) {
+  JavaScriptPrintingOptions options = new JavaScriptPrintingOptions(
+      shouldCompressOutput: true,
+      preferSemicolonToNewlineInMinifiedOutput: true);
+  LenientPrintingContext printingContext =
+      new LenientPrintingContext();
+  new Printer(options, printingContext).visit(node);
+  return printingContext.getText();
+}
+
+/// Visitor that creates an XML-like representation of the structure of a
+/// JavaScript [Node].
+class DebugPrinter extends BaseVisitor with Indentation, Tagging<Node> {
+  StringBuffer sb = new StringBuffer();
+
+  void visitNodeWithChildren(Node node, String type) {
+    openNode(node, type);
+    node.visitChildren(this);
+    closeNode();
+  }
+
+  @override
+  void visitNode(Node node) {
+    visitNodeWithChildren(node, '${node.runtimeType}');
+  }
+
+  @override
+  void visitName(Name node) {
+    openAndCloseNode(node, '${node.runtimeType}', {'name': node.name});
+  }
+
+  @override
+  void visitLiteralString(LiteralString node) {
+    openAndCloseNode(node, '${node.runtimeType}', {'value': node.value});
+  }
+
+  /**
+   * Pretty-prints given node tree into string.
+   */
+  static String prettyPrint(Node node) {
+    var p = new DebugPrinter();
+    node.accept(p);
+    return p.sb.toString();
+  }
+}
+
+/// Simple printing context that doesn't throw on errors.
+class LenientPrintingContext extends SimpleJavaScriptPrintingContext {
+  @override
+  void error(String message) {
+    buffer.write('>>$message<<');
+  }
+}