fix duplicate script issue

pkg/polymer/lib/src/build/import_inliner.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.
 
 /// Transfomer that inlines polymer-element definitions from html imports.
 library polymer.src.build.import_inliner;
 
 import 'dart:async';
 import 'dart:convert';
+import 'dart:collection' show LinkedHashSet;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:barback/barback.dart';
 import 'package:code_transformers/assets.dart';
 import 'package:code_transformers/messages/build_logger.dart';
 import 'package:path/path.dart' as path;
 import 'package:html5lib/dom.dart' show
     Document, DocumentFragment, Element, Node;
 import 'package:html5lib/dom_parsing.dart' show TreeVisitor;
 import 'package:source_maps/refactor.dart' show TextEditTransaction;
 import 'package:source_span/source_span.dart';
 
 import 'common.dart';
 import 'messages.dart';
 
 // TODO(sigmund): move to web_components package (dartbug.com/18037).
 class _HtmlInliner extends PolymerTransformer {
   final TransformOptions options;
   final Transform transform;
   final BuildLogger logger;
   final AssetId docId;
   final seen = new Set<AssetId>();
-  final scriptIds = <AssetId>[];
+  final scriptIds = new LinkedHashSet<AssetId>();
   final inlinedStylesheetIds = new Set<AssetId>();
   final extractedFiles = new Set<AssetId>();
   bool experimentalBootstrap = false;
   final Element importsWrapper = new Element.html('<div hidden></div>');
 
   /// The number of extracted inline Dart scripts. Used as a counter to give
   /// unique-ish filenames.
   int inlineScriptCounter = 0;
 
   _HtmlInliner(TransformOptions options, Transform transform)
@@ skipping 43 matching lines @@
 
       var output = transform.primaryInput;
       if (changed) output = new Asset.fromString(docId, document.outerHtml);
       transform.addOutput(output);
 
       // We produce a secondary asset with extra information for later phases.
       transform.addOutput(new Asset.fromString(
           docId.addExtension('._data'),
           JSON.encode({
             'experimental_bootstrap': experimentalBootstrap,
-            'script_ids': scriptIds,
+            'script_ids': scriptIds.toList(),
           }, toEncodable: (id) => id.serialize())));
 
       // Write out the logs collected by our [BuildLogger].
       if (options.injectBuildLogsInOutput) {
         return logger.writeOutput();
       }
     });
   }
 
   /// Visits imports in [document] and add the imported documents to documents.
@@ skipping 126 matching lines @@
   /// the script tags. Instead we remove them entirely.
   Future<bool> _removeScripts(Document doc) {
     bool changed = false;
     return Future.forEach(doc.querySelectorAll('script'), (script) {
       if (script.attributes['type'] == TYPE_DART) {
         changed = true;
         script.remove();
         var src = script.attributes['src'];
         var srcId = uriToAssetId(docId, src, logger, script.sourceSpan);
 
+        // No duplicates allowed!
+        if (scriptIds.contains(srcId)) {
+          logger.warning(SCRIPT_INCLUDED_MORE_THAN_ONCE.create({'url': src}),
+              span: script.sourceSpan);
+          return true;
+        }
+
         // We check for extractedFiles because 'hasInput' below is only true for
         // assets that existed before this transformer runs (hasInput is false
         // for files created by [_extractScripts]).
         if (extractedFiles.contains(srcId)) {
           scriptIds.add(srcId);
           return true;
         }
 
         return transform.hasInput(srcId).then((exists) {
           if (!exists) {
@@ skipping 298 matching lines @@
 /// style tag except these ones.
 const IGNORED_LINKED_STYLE_ATTRS =
     const ['charset', 'href', 'href-lang', 'rel', 'rev'];
 
 /// Global RegExp objects.
 final _INVALID_LIB_CHARS_REGEX = new RegExp('[^a-z0-9_]');
 final _NUM_REGEX = new RegExp('[0-9]');
 final _BINDING_REGEX = new RegExp(r'(({{.*}})|(\[\[.*\]\]))');
 
 _getSpan(SourceFile file, AstNode node) => file.span(node.offset, node.end);