Revise barback logging patch.

pkg/barback/lib/src/package_graph.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.package_graph;
 
 import 'dart:async';
 
 import 'asset_cascade.dart';
 import 'asset_id.dart';
 import 'asset_node.dart';
 import 'asset_set.dart';
-import 'barback_logger.dart';
 import 'build_result.dart';
 import 'errors.dart';
+import 'log.dart';
 import 'package_provider.dart';
 import 'pool.dart';
 import 'transformer.dart';
 import 'utils.dart';
 
 /// The collection of [AssetCascade]s for an entire application.
 ///
 /// This tracks each package's [AssetCascade] and routes asset requests between
 /// them.
 class PackageGraph {
   /// The provider that exposes asset and package information.
   final PackageProvider provider;
 
-  /// The logger used to report transformer log entries. If this is null, then
-  /// [_defaultLogger] will be used instead.
-  final BarbackLogger _logger;
-
   /// The [AssetCascade] for each package.
   final _cascades = <String, AssetCascade>{};
 
   /// The current [BuildResult] for each package's [AssetCascade].
   ///
   /// The result for a given package will be `null` if that [AssetCascade] is
   /// actively building.
   final _cascadeResults = <String, BuildResult>{};
 
   /// A stream that emits a [BuildResult] each time the build is completed,
@@ skipping 10 matching lines @@
   /// A stream that emits any errors from the graph or the transformers.
   ///
   /// This emits errors as they're detected. If an error occurs in one part of
   /// the graph, 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<BarbackException> get errors => _errors;
   Stream<BarbackException> _errors;
 
+  /// The stream of [LogEntry] objects used to report transformer log entries.
+  Stream<LogEntry> get log => _logController.stream;
+  final _logController = new StreamController<LogEntry>.broadcast();
+
   /// The most recent error emitted from a cascade's result stream.
   ///
   /// This is used to pipe an unexpected error from a build to the resulting
   /// [Future] returned by [getAllAssets].
   var _lastUnexpectedError;
 
   // TODO(nweiz): Allow transformers to declare themselves as "lightweight" or
   // "heavyweight" and adjust their restrictions appropriately. Simple
   // transformers may be very efficient to run in parallel, whereas dart2js uses
   // a lot of memory and should be run more sequentially.
   /// A pool that controls how many transformers may be applied at once.
   final Pool transformPool = new Pool(10);
 
   /// Creates a new [PackageGraph] that will transform assets in all packages
   /// made available by [provider].
-  PackageGraph(this.provider, {BarbackLogger logger})
-      : _logger = logger != null ? logger : new BarbackLogger() {
+  PackageGraph(this.provider) {
     for (var package in provider.packages) {
       var cascade = new AssetCascade(this, package);
       // The initial result for each cascade is "success" since the cascade
       // doesn't start building until some source in that graph is updated.
       _cascadeResults[package] = new BuildResult.success();
       _cascades[package] = cascade;
       cascade.onDirty.listen((_) {
         _cascadeResults[package] = null;
       });
 
-      cascade.onLog.listen(_logger.logEntry);
+      cascade.onLog.listen((entry) {
+        if (_logController.hasListener) {
+          _logController.add(entry);
+        } else {
+          // No listeners, so just print entry.
+          var buffer = new StringBuffer();
+          buffer.write("[${entry.level} ${entry.transform}] ");
+
+          if (entry.span != null) {
+            buffer.write(entry.span.getLocationMessage(entry.message));
+          } else {
+            buffer.write(entry.message);
+          }
+
+          print(buffer);
+        }
+      });
 
       cascade.results.listen((result) {
         _cascadeResults[cascade.package] = result;
         // If any cascade hasn't yet finished, the overall build isn't finished
         // either.
         if (_cascadeResults.values.any((result) => result == null)) return;
 
         // Include all build errors for all cascades. If no cascades have
         // errors, the result will automatically be considered a success.
         _resultsController.add(
@@ skipping 72 matching lines @@
       if (cascade == null) throw new ArgumentError("Unknown package $package.");
       cascade.removeSources(ids);
     });
   }
 
   void updateTransformers(String package,
       Iterable<Iterable<Transformer>> transformers) {
     _cascades[package].updateTransformers(transformers);
   }
 }