Improve barback/pub logging.

pkg/barback/lib/src/transform_node.dart

Index: pkg/barback/lib/src/transform_node.dart
diff --git a/pkg/barback/lib/src/transform_node.dart b/pkg/barback/lib/src/transform_node.dart
index 578b2fa20c8301b95cce949507f8ff91e626a5bd..56605c2617e63e8f9a877d96beb40cbace5d3eb5 100644
--- a/pkg/barback/lib/src/transform_node.dart
+++ b/pkg/barback/lib/src/transform_node.dart
@@ -10,6 +10,7 @@ import 'asset.dart';
 import 'asset_id.dart';
 import 'asset_node.dart';
 import 'asset_set.dart';
+import 'barback_logger.dart';
 import 'errors.dart';
 import 'phase.dart';
 import 'transform.dart';
@@ -53,6 +54,10 @@ class TransformNode {
   Stream get onDirty => _onDirtyController.stream;
   final _onDirtyController = new StreamController.broadcast(sync: true);
 
+  /// A stream that emits an event whenever this transform logs an entry.
+  Stream<LogEntry> get onLog => _onLogController.stream;
+  final _onLogController = new StreamController<LogEntry>.broadcast();
+
   TransformNode(this.phase, this.transformer, this.primary) {
     _primarySubscription = primary.onStateChange.listen((state) {
       if (state.isRemoved) {
@@ -106,7 +111,7 @@ class TransformNode {
     assert(!_onDirtyController.isClosed);
 
     var newOutputs = new AssetSet();
-    var transform = createTransform(this, newOutputs);
+    var transform = createTransform(this, newOutputs, _log);
 
     // Clear all the old input subscriptions. If an input is re-used, we'll
     // re-subscribe.
@@ -200,4 +205,12 @@ class TransformNode {
 
     return brandNewOutputs;
   }
+
+  void _log(AssetId asset, LogLevel level, String message, Span span) {
+    // If the log isn't already associated with an asset, use the primary.
+    if (asset == null) asset = primary.id;
+    var info = new TransformInfo(transformer, primary.id);

[nweiz, 2013/10/16 19:41:27]

There's already an info getter that does this.

[Bob Nystrom, 2013/10/28 23:45:56]

Done.

+    var entry = new LogEntry(info, asset, level, message, span);
+    _onLogController.add(entry);
+  }
 }