Add more metadata to non-programmatic barback exceptions.

pkg/barback/lib/src/asset_cascade.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.asset_cascade;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'asset.dart';
@@ skipping 48 matching lines @@
   Stream<BuildResult> get results => _resultsController.stream;
   final _resultsController = new StreamController<BuildResult>.broadcast();
 
   /// A stream that emits any errors from the cascade or the transformers.
   ///
   /// This emits errors as they're detected. If an error occurs in one part of
   /// the cascade, unrelated parts will continue building.
   ///
   /// This will not emit programming errors from barback itself. Those will be
   /// emitted through the [results] stream's error channel.
-  Stream get errors => _errorsController.stream;
-  final _errorsController = new StreamController.broadcast();
+  Stream<BarbackException> get errors => _errorsController.stream;
+  final _errorsController = new StreamController<BarbackException>.broadcast();
 
   /// The errors that have occurred since the current build started.
   ///
   /// This will be empty if no build is occurring.
-  Queue _accumulatedErrors;
+  Queue<BarbackException> _accumulatedErrors;
 
   /// A future that completes when the currently running build process finishes.
   ///
   /// If no build it in progress, is `null`.
   Future _processDone;
 
   /// Whether any source assets have been updated or removed since processing
   /// last began.
   var _newChanges = false;
 
@@ skipping 95 matching lines @@
       // return out-of-date contents for the asset.
       if (_loadingSources.containsKey(id)) _loadingSources[id].cancel();
 
       _loadingSources[id] =
           new CancelableFuture<Asset>(graph.provider.getAsset(id));
       _loadingSources[id].whenComplete(() {
         _loadingSources.remove(id);
       }).then((asset) {
         var controller = _sourceControllerMap[id].setAvailable(asset);
       }).catchError((error) {
-        reportError(error);
+        reportError(new AssetLoadException(id, error));
 
         // TODO(nweiz): propagate error information through asset nodes.
         _sourceControllerMap.remove(id).setRemoved();
       });
     }
   }
 
   /// Removes [removed] from the graph's known set of source assets.
   void removeSources(Iterable<AssetId> removed) {
     removed.forEach((id) {
       // If the source was being loaded, cancel that load.
       if (_loadingSources.containsKey(id)) _loadingSources.remove(id).cancel();
 
       var controller = _sourceControllerMap.remove(id);
       // Don't choke if an id is double-removed for some reason.
       if (controller != null) controller.setRemoved();
     });
   }
 
-  void reportError(error) {
+  void reportError(BarbackException error) {
     _accumulatedErrors.add(error);
     _errorsController.add(error);
   }
 
   /// Starts the build process asynchronously if there is work to be done.
   ///
   /// Returns a future that completes with the background processing is done.
   /// If there is no work to do, returns a future that completes immediately.
   /// All errors that occur during processing will be caught (and routed to the
   /// [results] stream) before they get to the returned future, so it is safe
@@ skipping 42 matching lines @@
 
         // Otherwise, everything is done.
         return;
       }
 
       // Process that phase and then loop onto the next.
       return future.then((_) => _process());
     });
   }
 }