Make pub build use barback.

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 103 matching lines @@
 
   /// Creates a new [AssetCascade].
   ///
   /// It loads source assets within [package] using [provider].
   AssetCascade(this.graph, this.package) {
     _onDirtyPool.add(_onDirtyController.stream);
     _addPhase(new Phase(this, []));
 
     // Keep track of logged errors so we can know that the build failed.
     onLog.listen((entry) {
-      if (entry.level == LogLevel.ERROR) _numLogErrors++;
+      if (entry.level == LogLevel.ERROR) {
+        _accumulatedErrors.add(
+            new TransformerException(entry.transform, entry.message));
+      }
     });
   }
 
   /// Gets the asset identified by [id].
   ///
   /// If [id] is for a generated or transformed asset, this will wait until it
   /// has been created and return it. This means that the returned asset will
   /// always be [AssetState.AVAILABLE].
   ///
   /// If the asset cannot be found, returns null.
@@ skipping 119 matching lines @@
   /// to discard it.
   Future _waitForProcess() {
     if (_processDone != null) return _processDone;
 
     _accumulatedErrors = new Queue();
     _numLogErrors = 0;
     return _processDone = _process().then((_) {
       // Report the build completion.
       // TODO(rnystrom): Put some useful data in here.
       _resultsController.add(
-          new BuildResult(_accumulatedErrors, _numLogErrors));
+          new BuildResult(_accumulatedErrors));
     }).catchError((error) {
       // If we get here, it's an unexpected error. Runtime errors like missing
       // assets should be handled earlier. Errors from transformers or other
       // external code that barback calls into should be caught at that API
       // boundary.
       //
       // On the off chance we get here, pipe the error to the results stream
       // as an error. That will let applications handle it without it appearing
       // in the same path as "normal" errors that get reported.
       _resultsController.addError(error);
@@ skipping 23 matching lines @@
 
         // Otherwise, everything is done.
         return;
       }
 
       // Process that phase and then loop onto the next.
       return future.then((_) => _process());
     });
   }
 }