Reorganize barback's source files.

pkg/barback/lib/src/transform_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.transform_logger;
-
-import 'package:source_maps/span.dart';
-
-import 'asset_id.dart';
-import 'log.dart';
-
-typedef void LogFunction(AssetId asset, LogLevel level, String message,
-                         Span span);
-
-/// Object used to report warnings and errors encountered while running a
-/// transformer.
-class TransformLogger {
-  final LogFunction _logFunction;
-
-  TransformLogger(this._logFunction);
-
-  /// Logs an informative message.
-  ///
-  /// If [asset] is provided, the log entry is associated with that asset.
-  /// Otherwise it's associated with the primary input of [transformer].
-  /// If [span] is provided, indicates the location in the input asset that
-  /// caused the message.
-  void info(String message, {AssetId asset, Span span}) {
-    _logFunction(asset, LogLevel.INFO, message, span);
-  }
-
-  /// Logs a message that won't be displayed unless the user is running in
-  /// verbose mode.
-  ///
-  /// If [asset] is provided, the log entry is associated with that asset.
-  /// Otherwise it's associated with the primary input of [transformer].
-  /// If [span] is provided, indicates the location in the input asset that
-  /// caused the message.
-  void fine(String message, {AssetId asset, Span span}) {
-    _logFunction(asset, LogLevel.FINE, message, span);
-  }
-
-  /// Logs a warning message.
-  ///
-  /// If [asset] is provided, the log entry is associated with that asset.
-  /// Otherwise it's associated with the primary input of [transformer].
-  /// If present, [span] indicates the location in the input asset that caused
-  /// the warning.
-  void warning(String message, {AssetId asset, Span span}) {
-    _logFunction(asset, LogLevel.WARNING, message, span);
-  }
-
-  /// Logs an error message.
-  ///
-  /// If [asset] is provided, the log entry is associated with that asset.
-  /// Otherwise it's associated with the primary input of [transformer].
-  /// If present, [span] indicates the location in the input asset that caused
-  /// the error.
-  ///
-  /// Logging any errors will cause Barback to consider the transformation to
-  /// have failed, much like throwing an exception. This means that neither the
-  /// primary input nor any outputs emitted by the transformer will be passed on
-  /// to the following phase, and the build will be reported as having failed.
-  ///
-  /// Unlike throwing an exception, this doesn't cause a transformer to stop
-  /// running. This makes it useful in cases where a single input may have
-  /// multiple errors that the user wants to know about.
-  void error(String message, {AssetId asset, Span span}) {
-    _logFunction(asset, LogLevel.ERROR, message, span);
-  }
-}