Stop running pub get at gclient sync time and fix build bugs

mojo/public/dart/third_party/barback/lib/src/graph/phase_output.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.graph.phase_output;
+
+import 'dart:async';
+import 'dart:collection';
+
+import '../asset/asset_forwarder.dart';
+import '../asset/asset_node.dart';
+import '../errors.dart';
+import 'phase.dart';
+
+/// A class that handles a single output of a phase.
+///
+/// Normally there's only a single [AssetNode] for a phase's output, but it's
+/// possible that multiple transformers in the same phase emit assets with the
+/// same id, causing collisions. This handles those collisions by forwarding the
+/// chronologically first asset.
+///
+/// When the asset being forwarding changes, the old value of [output] will be
+/// marked as removed and a new value will replace it. Users of this class can
+/// be notified of this using [onAsset].
+class PhaseOutput {
+  /// The phase for which this is an output.
+  final Phase _phase;
+
+  /// A string describing the location of [this] in the transformer graph.
+  final String _location;
+
+  /// The asset node for this output.
+  AssetNode get output => _outputForwarder.node;
+  AssetForwarder _outputForwarder;
+
+  /// A stream that emits an [AssetNode] each time this output starts forwarding
+  /// a new asset.
+  Stream<AssetNode> get onAsset => _onAssetController.stream;
+  final _onAssetController =
+      new StreamController<AssetNode>.broadcast(sync: true);
+
+  /// The assets for this output.
+  ///
+  /// If there's no collision, this will only have one element. Otherwise, it
+  /// will be ordered by which asset was added first.
+  final _assets = new Queue<AssetNode>();
+
+  /// The [AssetCollisionException] for this output, or null if there is no
+  /// collision currently.
+  AssetCollisionException get collisionException {
+    if (_assets.length == 1) return null;
+    return new AssetCollisionException(
+        _assets.where((asset) => asset.transform != null)
+            .map((asset) => asset.transform.info),
+        output.id);
+  }
+
+  PhaseOutput(this._phase, AssetNode output, this._location)
+      : _outputForwarder = new AssetForwarder(output) {
+    assert(!output.state.isRemoved);
+    add(output);
+  }
+
+  /// Adds an asset node as an output with this id.
+  void add(AssetNode node) {
+    assert(node.id == output.id);
+    assert(!output.state.isRemoved);
+    _assets.add(node);
+    _watchAsset(node);
+  }
+
+  /// Removes all existing listeners on [output] without actually closing
+  /// [this].
+  ///
+  /// This marks [output] as removed, but immediately replaces it with a new
+  /// [AssetNode] in the same state as the old output. This is used when adding
+  /// a new [Phase] to cause consumers of the prior phase's outputs to be to
+  /// start consuming the new phase's outputs instead.
+  void removeListeners() {
+    _outputForwarder.close();
+    _outputForwarder = new AssetForwarder(_assets.first);
+    _onAssetController.add(output);
+  }
+
+  /// Watches [node] to adjust [_assets] and [output] when it's removed.
+  void _watchAsset(AssetNode node) {
+    node.whenRemoved(() {
+      if (_assets.length == 1) {
+        assert(_assets.single == node);
+        _outputForwarder.close();
+        _onAssetController.close();
+        return;
+      }
+
+      // If there was more than one asset, we're resolving a collision --
+      // possibly partially.
+      var wasFirst = _assets.first == node;
+      _assets.remove(node);
+
+      // If this was the first asset, we replace it with the next asset
+      // (chronologically).
+      if (wasFirst) removeListeners();
+
+      // If there's still a collision, report it. This lets the user know if
+      // they've successfully resolved the collision or not.
+      if (_assets.length > 1) {
+        // TODO(nweiz): report this through the output asset.
+        _phase.cascade.reportError(collisionException);
+      }
+    });
+  }
+
+  String toString() => "phase output in $_location for $output";
+}