Improve barback/pub logging.

pkg/barback/lib/src/barback_logger.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.barback_logger;
+
+import 'package:source_maps/span.dart';
+
+import 'asset_id.dart';
+import 'errors.dart';
+
+/// Object used to report warnings and errors encountered while running a
+/// transformer.
+class BarbackLogger {
+  /// Logs [entry].
+  void logEntry(LogEntry entry) {

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

I'd rather just call this "log". "logEntry" reads as a noun to me, which is
weird for a method name.

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

In pub, we import log.dart with a "log" prefix, so implementing this class in
pub is nasty if the method is called "log" too. :-/

My intent is for the method to read like "log entry" where "log" is the verb.
It's not ideal.

[nweiz, 2013/10/29 00:40:13]

Does it actually cause a conflict to define a method with the same name as a
prefix that's in scope? That seems like it should be fine.

[Bob Nystrom, 2013/10/29 18:29:45]

It doesn't conflict, it wins. So you have to do "this.log" to get to the method.

Removed this class, though, so done.

+    var buffer = new StringBuffer();
+    buffer.write("[${entry.level} ${entry.transform}] ");
+
+    var message = entry.message;

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

Unused variable.

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

Done.

+    if (entry.span == null) {

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

!=

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

Eek. Done.

+      buffer.write(entry.span.getLocationMessage(entry.message));
+    } else {
+      buffer.write(message);
+    }
+
+    print(buffer);
+  }
+}
+
+/// The severity of a logged message.
+class LogLevel {

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

Do we want to have a FINE level as well?

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

Sure, I just added the ones I needed for dart2js, but we can expand this over
time.

+  static const INFO = const LogLevel("Info");
+  static const WARNING = const LogLevel("Warning");
+  static const ERROR = const LogLevel("Error");
+
+  final String name;
+  const LogLevel(this.name);
+
+  String toString() => name;
+}
+
+/// One message logged during a transform.
+class LogEntry {
+  /// The transform that logged the message.
+  final TransformInfo transform;
+
+  /// The asset that the message is associated with.
+  final AssetId asset;

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

I'd call this "assetId", since Asset is a different public class.

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

Done.

+
+  final LogLevel level;
+  final String message;
+
+  /// The location that the message pertains to or null if not associated with
+  /// a source [Span].
+  final Span span;
+
+  LogEntry(this.transform, this.asset, this.level, this.message, this.span);
+}