Handle synchronous asset load errors in barback.

pkg/barback/test/utils.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.
 
 library barback.test.utils;
 
 import 'dart:async';
 import 'dart:convert' show Encoding;
 
 import 'package:barback/barback.dart';
@@ skipping 140 matching lines @@
 /// Does not update it in the graph.
 void modifyAsset(String name, String contents) {
   schedule(() {
     _provider._modifyAsset(name, contents);
   }, "modify asset $name");
 }
 
 /// Schedules an error to be generated when loading the asset identified by
 /// [name].
 ///
-/// Does not update the asset in the graph.
-void setAssetError(String name) {
+/// Does not update the asset in the graph. If [async] is true, the error is
+/// thrown asynchronously.
+void setAssetError(String name, {bool async: true}) {
   schedule(() {
-    _provider._setAssetError(name);
+    _provider._setAssetError(name, async);
   }, "set error for asset $name");
 }
 
 /// Schedules a pause of the internally created [PackageProvider].
 ///
 /// All asset requests that the [PackageGraph] makes to the provider after this
 /// will not complete until [resumeProvider] is called.
 void pauseProvider() {
   schedule(() => _provider._pause(), "pause provider");
 }
@@ skipping 288 matching lines @@
 /// An [AssetProvider] that provides the given set of assets.
 class MockProvider implements PackageProvider {
   Iterable<String> get packages => _assets.keys;
 
   final Map<String, AssetSet> _assets;
 
   /// The set of assets for which [MockLoadException]s should be emitted if
   /// they're loaded.
   final _errors = new Set<AssetId>();
 
+  /// The set of assets for which synchronous [MockLoadException]s should be
+  /// emitted if they're loaded.
+  final _syncErrors = new Set<AssetId>();
+
   /// The completer that [getAsset()] is waiting on to complete when paused.
   ///
   /// If `null` it will return the asset immediately.
   Completer _pauseCompleter;
 
   /// Tells the provider to wait during [getAsset] until [complete()]
   /// is called.
   ///
   /// Lets you test the asynchronous behavior of loading.
   void _pause() {
@@ skipping 37 matching lines @@
 
     // If there are no assets or transformers, add a dummy package. This better
     // simulates the real world, where there'll always be at least the
     // entrypoint package.
     return assetMap.isEmpty ? {"app": new AssetSet()} : assetMap;
   }
 
   void _modifyAsset(String name, String contents) {
     var id = new AssetId.parse(name);
     _errors.remove(id);
+    _syncErrors.remove(id);
     (_assets[id.package][id] as _MockAsset).contents = contents;
   }
 
-  void _setAssetError(String name) {
-    _errors.add(new AssetId.parse(name));
+  void _setAssetError(String name, bool async) {
+    (async ? _errors : _syncErrors).add(new AssetId.parse(name));
   }
 
   List<AssetId> listAssets(String package, {String within}) {
     if (within != null) {
       throw new UnimplementedError("Doesn't handle 'within' yet.");
     }
 
     return _assets[package].map((asset) => asset.id);
   }
 
   Future<Asset> getAsset(AssetId id) {
     // Eagerly load the asset so we can test an asset's value changing between
     // when a load starts and when it finishes.
     var assets = _assets[id.package];
     var asset;
     if (assets != null) asset = assets[id];
 
+    if (_syncErrors.contains(id)) throw new MockLoadException(id);
     var hasError = _errors.contains(id);
 
     var future;
     if (_pauseCompleter != null) {
       future = _pauseCompleter.future;
     } else {
       future = new Future.value();
     }
 
     return future.then((_) {
@@ skipping 20 matching lines @@
 
   _MockAsset(this.id, this.contents);
 
   Future<String> readAsString({Encoding encoding}) =>
       new Future.value(contents);
 
   Stream<List<int>> read() => throw new UnimplementedError();
 
   String toString() => "MockAsset $id $contents";
 }