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barback/lib/src/graph/transform_node.dart

Index: barback/lib/src/graph/transform_node.dart
diff --git a/barback/lib/src/graph/transform_node.dart b/barback/lib/src/graph/transform_node.dart
deleted file mode 100644
index 2a24335b612077348302493624974e477670bdfb..0000000000000000000000000000000000000000
--- a/barback/lib/src/graph/transform_node.dart
+++ /dev/null
@@ -1,923 +0,0 @@
-// 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.transform_node;
-
-import 'dart:async';
-
-import '../asset/asset.dart';
-import '../asset/asset_id.dart';
-import '../asset/asset_node.dart';
-import '../asset/asset_node_set.dart';
-import '../errors.dart';
-import '../log.dart';
-import '../transformer/aggregate_transform.dart';
-import '../transformer/aggregate_transformer.dart';
-import '../transformer/declaring_aggregate_transform.dart';
-import '../transformer/declaring_aggregate_transformer.dart';
-import '../transformer/lazy_aggregate_transformer.dart';
-import '../utils.dart';
-import 'node_status.dart';
-import 'node_streams.dart';
-import 'phase.dart';
-import 'transformer_classifier.dart';
-
-/// Every `_applyLogDuration`, we will issue a fine log entry letting the user
-/// know that the transform is still executing.
-const _applyLogDuration = const Duration(seconds: 10);
-
-/// Describes a transform on a set of assets and its relationship to the build
-/// dependency graph.
-///
-/// Keeps track of whether it's dirty and needs to be run and which assets it
-/// depends on.
-class TransformNode {
-  /// The aggregate key for this node.
-  final String key;
-
-  /// The [TransformerClassifier] that [this] belongs to.
-  final TransformerClassifier classifier;
-
-  /// The [Phase] that this transform runs in.
-  Phase get phase => classifier.phase;
-
-  /// The [AggregateTransformer] to apply to this node's inputs.
-  final AggregateTransformer transformer;
-
-  /// The primary asset nodes this transform runs on.
-  final _primaries = new AssetNodeSet();
-
-  /// A string describing the location of [this] in the transformer graph.
-  final String _location;
-
-  /// The subscription to the [_primaries]' [AssetNode.onStateChange] streams.
-  final _primarySubscriptions = new Map<AssetId, StreamSubscription>();
-
-  /// The subscription to [phase]'s [Phase.onAsset] stream.
-  StreamSubscription<AssetNode> _phaseAssetSubscription;
-
-  /// The subscription to [phase]'s [Phase.onStatusChange] stream.
-  StreamSubscription<NodeStatus> _phaseStatusSubscription;
-
-  /// How far along [this] is in processing its assets.
-  NodeStatus get status {
-    if (_state == _State.APPLIED || _state == _State.DECLARED) {
-      return NodeStatus.IDLE;
-    }
-
-    if (_declaring && _state != _State.DECLARING &&
-        _state != _State.NEEDS_DECLARE) {
-      return NodeStatus.MATERIALIZING;
-    } else {
-      return NodeStatus.RUNNING;
-    }
-  }
-
-  /// The [TransformInfo] describing this node.
-  ///
-  /// [TransformInfo] is the publicly-visible representation of a transform
-  /// node.
-  TransformInfo get info => new TransformInfo(transformer,
-      new AssetId(phase.cascade.package, key));
-
-  /// Whether this is a declaring transform.
-  ///
-  /// This is usually identical to `transformer is
-  /// DeclaringAggregateTransformer`, but if a declaring and non-lazy
-  /// transformer emits an error during `declareOutputs` it's treated as though
-  /// it wasn't declaring.
-  bool get _declaring => transformer is DeclaringAggregateTransformer &&
-      (_state == _State.DECLARING || _declaredOutputs != null);
-
-  /// Whether this transform has been forced since it last finished applying.
-  ///
-  /// A transform being forced means it should run until it generates outputs
-  /// and is no longer dirty. This is always true for non-declaring
-  /// transformers, since they always need to eagerly generate outputs.
-  bool _forced;
-
-  /// The subscriptions to each secondary input's [AssetNode.onStateChange]
-  /// stream.
-  final _secondarySubscriptions = new Map<AssetId, StreamSubscription>();
-
-  /// The subscriptions to the [AssetCascade.onAsset] stream for cascades that
-  /// might generate assets in [_missingInputs].
-  final _missingExternalInputSubscriptions =
-      new Map<String, StreamSubscription>();
-
-  /// The controllers for the asset nodes emitted by this node.
-  final _outputControllers = new Map<AssetId, AssetNodeController>();
-
-  /// The ids of inputs the transformer tried and failed to read last time it
-  /// ran.
-  final _missingInputs = new Set<AssetId>();
-
-  /// The controllers that are used to pass each primary input through [this] if
-  /// it's not consumed or overwritten.
-  ///
-  /// This needs an intervening controller to ensure that the output can be
-  /// marked dirty when determining whether [this] will consume or overwrite it,
-  /// and be marked removed if it does. No pass-through controller will exist
-  /// for primary inputs that are not being passed through.
-  final _passThroughControllers = new Map<AssetId, AssetNodeController>();
-
-  /// The asset node for this transform.
-  final _streams = new NodeStreams();
-  Stream<NodeStatus> get onStatusChange => _streams.onStatusChange;
-  Stream<AssetNode> get onAsset => _streams.onAsset;
-  Stream<LogEntry> get onLog => _streams.onLog;
-
-  /// The current state of [this].
-  var _state = _State.DECLARED;
-
-  /// Whether [this] has been marked as removed.
-  bool get _isRemoved => _streams.onAssetController.isClosed;
-
-  // If [transformer] is declaring but not lazy and [primary] is available, we
-  // can run [apply] even if [force] hasn't been called, since [transformer]
-  // should run eagerly if possible.
-  bool get _canRunDeclaringEagerly =>
-      _declaring && transformer is! LazyAggregateTransformer &&
-      _primaries.every((input) => input.state.isAvailable);
-
-  /// Which primary inputs the most recent run of this transform has declared
-  /// that it consumes.
-  ///
-  /// This starts out `null`, indicating that the transform hasn't declared
-  /// anything yet. This is not meaningful unless [_state] is [_State.APPLIED]
-  /// or [_State.DECLARED].
-  Set<AssetId> _consumedPrimaries;
-
-  /// The set of output ids that [transformer] declared it would emit.
-  ///
-  /// This is only non-null if [transformer] is a
-  /// [DeclaringAggregateTransformer] and its [declareOutputs] has been run
-  /// successfully.
-  Set<AssetId> _declaredOutputs;
-
-  /// The controller for the currently-running
-  /// [DeclaringAggregateTransformer.declareOutputs] call's
-  /// [DeclaringAggregateTransform].
-  ///
-  /// This will be non-`null` when
-  /// [DeclaringAggregateTransformer.declareOutputs] is running. This means that
-  /// it's always non-`null` when [_state] is [_State.DECLARING], sometimes
-  /// non-`null` when it's [_State.NEEDS_DECLARE], and always `null` otherwise.
-  DeclaringAggregateTransformController _declareController;
-
-  /// The controller for the currently-running [AggregateTransformer.apply]
-  /// call's [AggregateTransform].
-  ///
-  /// This will be non-`null` when [AggregateTransform.apply] is running, which
-  /// means that it's always non-`null` when [_state] is [_State.APPLYING] or
-  /// [_State.NEEDS_APPLY], sometimes non-`null` when it's
-  /// [_State.NEEDS_DECLARE], and always `null` otherwise.
-  AggregateTransformController _applyController;
-
-  /// Map to track pending requests for secondary inputs.
-  ///
-  /// Keys are the secondary inputs that have been requested but not yet
-  /// produced. Values are the number of requests for that input.
-  final _pendingSecondaryInputs = <AssetId, int>{};
-
-  /// A stopwatch that tracks the total time spent in a transformer's `apply`
-  /// function.
-  final _timeInTransformer = new Stopwatch();
-
-  /// A stopwatch that tracks the time in a transformer's `apply` function spent
-  /// waiting for [getInput] calls to complete.
-  final _timeAwaitingInputs = new Stopwatch();
-
-  TransformNode(this.classifier, this.transformer, this.key, this._location) {
-    _forced = transformer is! DeclaringAggregateTransformer;
-
-    _phaseAssetSubscription = phase.previous.onAsset.listen((node) {
-      if (!_missingInputs.contains(node.id)) return;
-      if (_forced) node.force();
-      _dirty();
-    });
-
-    _phaseStatusSubscription = phase.previous.onStatusChange.listen((status) {
-      if (status == NodeStatus.RUNNING) return;
-
-      _maybeFinishDeclareController();
-      _maybeFinishApplyController();
-    });
-
-    classifier.onDoneClassifying.listen((_) {
-      _maybeFinishDeclareController();
-      _maybeFinishApplyController();
-    });
-
-    _run();
-  }
-
-  /// Adds [input] as a primary input for this node.
-  void addPrimary(AssetNode input) {
-    _primaries.add(input);
-    if (_forced) input.force();
-
-    _primarySubscriptions[input.id] = input.onStateChange
-        .listen((_) => _onPrimaryStateChange(input));
-
-    if (_state == _State.DECLARING && !_declareController.isDone) {
-      // If we're running `declareOutputs` and its id stream isn't closed yet,
-      // pass this in as another id.
-      _declareController.addId(input.id);
-      _maybeFinishDeclareController();
-    } else if (_state == _State.APPLYING) {
-      // If we're running `apply`, we need to wait until [input] is available
-      // before we pass it into the stream. If it's available now, great; if
-      // not, [_onPrimaryStateChange] will handle it.
-      if (!input.state.isAvailable) {
-        // If we started running eagerly without being forced, abort that run if
-        // a new unavailable asset comes in.
-        if (input.isLazy && !_forced) _restartRun();
-        return;
-      }
-
-      _onPrimaryStateChange(input);
-      _maybeFinishApplyController();
-    } else {
-      // Otherwise, a new input means we'll need to re-run `declareOutputs`.
-      _restartRun();
-    }
-  }
-
-  /// Marks this transform as removed.
-  ///
-  /// This causes all of the transform's outputs to be marked as removed as
-  /// well. Normally this will be automatically done internally based on events
-  /// from the primary input, but it's possible for a transform to no longer be
-  /// valid even if its primary input still exists.
-  void remove() {
-    _streams.close();
-    _phaseAssetSubscription.cancel();
-    _phaseStatusSubscription.cancel();
-    if (_declareController != null) _declareController.cancel();
-    if (_applyController != null) _applyController.cancel();
-    _clearSecondarySubscriptions();
-    _clearOutputs();
-
-    for (var subscription in _primarySubscriptions.values) {
-      subscription.cancel();
-    }
-    _primarySubscriptions.clear();
-
-    for (var controller in _passThroughControllers.values) {
-      controller.setRemoved();
-    }
-    _passThroughControllers.clear();
-  }
-
-  /// If [this] is deferred, ensures that its concrete outputs will be
-  /// generated.
-  void force() {
-    if (_forced || _state == _State.APPLIED) return;
-    for (var input in _primaries) {
-      input.force();
-    }
-
-    _forced = true;
-    if (_state == _State.DECLARED) _apply();
-  }
-
-  /// Marks this transform as dirty.
-  ///
-  /// Specifically, this should be called when one of the transform's inputs'
-  /// contents change, or when a secondary input is removed. Primary inputs
-  /// being added or removed are handled by [addInput] and
-  /// [_onPrimaryStateChange].
-  void _dirty() {
-    if (_state == _State.DECLARING || _state == _State.NEEDS_DECLARE ||
-        _state == _State.NEEDS_APPLY) {
-      // If we already know that [_apply] needs to be run, there's nothing to do
-      // here.
-      return;
-    }
-
-    if (!_forced && !_canRunDeclaringEagerly) {
-      // [forced] should only ever be false for a declaring transformer.
-      assert(_declaring);
-
-      // If we've finished applying, transition to DECLARED, indicating that we
-      // know what outputs [apply] will emit but we're waiting to emit them
-      // concretely until [force] is called. If we're still applying, we'll
-      // transition to DECLARED once we finish.
-      if (_state == _State.APPLIED) _state = _State.DECLARED;
-      for (var controller in _outputControllers.values) {
-        controller.setLazy(force);
-      }
-      _emitDeclaredOutputs();
-      return;
-    }
-
-    if (_state == _State.APPLIED) {
-      if (_declaredOutputs != null) _emitDeclaredOutputs();
-      _apply();
-    } else if (_state == _State.DECLARED) {
-      _apply();
-    } else {
-      _state = _State.NEEDS_APPLY;
-    }
-  }
-
-  /// The callback called when [input]'s state changes.
-  void _onPrimaryStateChange(AssetNode input) {
-    if (input.state.isRemoved) {
-      _primarySubscriptions.remove(input.id);
-
-      if (_primaries.isEmpty) {
-        // If there are no more primary inputs, there's no more use for this
-        // node in the graph. It will be re-created by its
-        // [TransformerClassifier] if a new input with [key] is added.
-        remove();
-        return;
-      }
-
-      // Any change to the number of primary inputs requires that we re-run the
-      // transformation.
-      _restartRun();
-    } else if (input.state.isAvailable) {
-      if (_state == _State.DECLARED) {
-        // If we're passing through this input and its contents don't matter,
-        // update the pass-through controller.
-        var controller = _passThroughControllers[input.id];
-        if (controller != null) controller.setAvailable(input.asset);
-      }
-
-      if (_state == _State.DECLARED && _canRunDeclaringEagerly) {
-        // If [this] is fully declared but hasn't started applying, this input
-        // becoming available may mean that all inputs are available, in which
-        // case we can run apply eagerly.
-        _apply();
-        return;
-      }
-
-      // If we're not actively passing concrete assets to the transformer, the
-      // distinction between a dirty asset and an available one isn't relevant.
-      if (_state != _State.APPLYING) return;
-
-      if (_applyController.isDone) {
-        // If we get a new asset after we've closed the asset stream, we need to
-        // re-run declare and then apply.
-        _restartRun();
-      } else {
-        // If the new asset comes before the asset stream is done, we can just
-        // pass it to the stream.
-        _applyController.addInput(input.asset);
-        _maybeFinishApplyController();
-      }
-    } else {
-      if (_forced) input.force();
-
-      var controller = _passThroughControllers[input.id];
-      if (controller != null) controller.setDirty();
-
-      if (_state == _State.APPLYING && !_applyController.addedId(input.id) &&
-          (_forced || !input.isLazy)) {
-        // If the input hasn't yet been added to the transform's input stream,
-        // there's no need to consider the transformation dirty. However, if the
-        // input is lazy and we're running eagerly, we need to restart the
-        // transformation.
-        return;
-      }
-      _dirty();
-    }
-  }
-
-  /// Run the entire transformation, including both `declareOutputs` (if
-  /// applicable) and `apply`.
-  void _run() {
-    assert(_state != _State.DECLARING);
-    assert(_state != _State.APPLYING);
-
-    _markOutputsDirty();
-    _declareOutputs(() {
-      if (_forced || _canRunDeclaringEagerly) {
-        _apply();
-      } else {
-        _state = _State.DECLARED;
-        _streams.changeStatus(NodeStatus.IDLE);
-      }
-    });
-  }
-
-  /// Restart the entire transformation, including `declareOutputs` if
-  /// applicable.
-  void _restartRun() {
-    if (_state == _State.DECLARED || _state == _State.APPLIED) {
-      // If we're currently idle, we can restart the transformation immediately.
-      _run();
-      return;
-    }
-
-    // If we're actively running `declareOutputs` or `apply`, cancel the
-    // transforms and transition to `NEEDS_DECLARE`. Once the transformer's
-    // method returns, we'll transition to `DECLARING`.
-    if (_declareController != null) _declareController.cancel();
-    if (_applyController != null) _applyController.cancel();
-    _state = _State.NEEDS_DECLARE;
-  }
-
-  /// Runs [transform.declareOutputs] and emits the resulting assets as dirty
-  /// assets.
-  ///
-  /// Calls [callback] when it's finished. This doesn't return a future so that
-  /// [callback] is called synchronously if there are no outputs to declare. If
-  /// [this] is removed while inputs are being declared, [callback] will not be
-  /// called.
-  void _declareOutputs(void callback()) {
-    if (transformer is! DeclaringAggregateTransformer) {
-      callback();
-      return;
-    }
-
-    _state = _State.DECLARING;
-    var controller = new DeclaringAggregateTransformController(this);
-    _declareController = controller;
-    _streams.onLogPool.add(controller.onLog);
-    for (var primary in _primaries) {
-      controller.addId(primary.id);
-    }
-    _maybeFinishDeclareController();
-
-    syncFuture(() {
-      return (transformer as DeclaringAggregateTransformer)
-          .declareOutputs(controller.transform);
-    }).whenComplete(() {
-      // Cancel the controller here even if `declareOutputs` wasn't interrupted.
-      // Since the declaration is finished, we want to close out the
-      // controller's streams.
-      controller.cancel();
-      _declareController = null;
-    }).then((_) {
-      if (_isRemoved) return;
-      if (_state == _State.NEEDS_DECLARE) {
-        _declareOutputs(callback);
-        return;
-      }
-
-      if (controller.loggedError) {
-        // If `declareOutputs` fails, fall back to treating a declaring
-        // transformer as though it were eager.
-        if (transformer is! LazyAggregateTransformer) _forced = true;
-        callback();
-        return;
-      }
-
-      _consumedPrimaries = controller.consumedPrimaries;
-      _declaredOutputs = controller.outputIds;
-      var invalidIds = _declaredOutputs
-          .where((id) => id.package != phase.cascade.package).toSet();
-      for (var id in invalidIds) {
-        _declaredOutputs.remove(id);
-        // TODO(nweiz): report this as a warning rather than a failing error.
-        phase.cascade.reportError(new InvalidOutputException(info, id));
-      }
-
-      for (var primary in _primaries) {
-        if (_declaredOutputs.contains(primary.id)) continue;
-        _passThrough(primary.id);
-      }
-      _emitDeclaredOutputs();
-      callback();
-    }).catchError((error, stackTrace) {
-      if (_isRemoved) return;
-      if (transformer is! LazyAggregateTransformer) _forced = true;
-      phase.cascade.reportError(_wrapException(error, stackTrace));
-      callback();
-    });
-  }
-
-  /// Emits a dirty asset node for all outputs that were declared by the
-  /// transformer.
-  ///
-  /// This won't emit any outputs for which there already exist output
-  /// controllers. It should only be called for transforms that have declared
-  /// their outputs.
-  void _emitDeclaredOutputs() {
-    assert(_declaredOutputs != null);
-    for (var id in _declaredOutputs) {
-      if (_outputControllers.containsKey(id)) continue;
-      var controller = _forced
-          ? new AssetNodeController(id, this)
-          : new AssetNodeController.lazy(id, force, this);
-      _outputControllers[id] = controller;
-      _streams.onAssetController.add(controller.node);
-    }
-  }
-
-  //// Mark all emitted and passed-through outputs of this transform as dirty.
-  void _markOutputsDirty() {
-    for (var controller in _passThroughControllers.values) {
-      controller.setDirty();
-    }
-    for (var controller in _outputControllers.values) {
-      if (_forced) {
-        controller.setDirty();
-      } else {
-        controller.setLazy(force);
-      }
-    }
-  }
-
-  /// Applies this transform.
-  void _apply() {
-    assert(!_isRemoved);
-
-    _markOutputsDirty();
-    _clearSecondarySubscriptions();
-    _state = _State.APPLYING;
-    _streams.changeStatus(status);
-    _runApply().then((hadError) {
-      if (_isRemoved) return;
-
-      if (_state == _State.DECLARED) return;
-
-      if (_state == _State.NEEDS_DECLARE) {
-        _run();
-        return;
-      }
-
-      // If an input's contents changed while running `apply`, retry unless the
-      // transformer is deferred and hasn't been forced.
-      if (_state == _State.NEEDS_APPLY) {
-        if (_forced || _canRunDeclaringEagerly) {
-          _apply();
-        } else {
-          _state = _State.DECLARED;
-        }
-        return;
-      }
-
-      if (_declaring) _forced = false;
-
-      assert(_state == _State.APPLYING);
-      if (hadError) {
-        _clearOutputs();
-        // If the transformer threw an error, we don't want to emit the
-        // pass-through assets in case they'll be overwritten by the
-        // transformer. However, if the transformer declared that it wouldn't
-        // overwrite or consume a pass-through asset, we can safely emit it.
-        if (_declaredOutputs != null) {
-          for (var input in _primaries) {
-            if (_consumedPrimaries.contains(input.id) ||
-                _declaredOutputs.contains(input.id)) {
-              _consumePrimary(input.id);
-            } else {
-              _passThrough(input.id);
-            }
-          }
-        }
-      }
-
-      _state = _State.APPLIED;
-      _streams.changeStatus(NodeStatus.IDLE);
-    });
-  }
-
-  /// Gets the asset for an input [id].
-  ///
-  /// If an input with [id] cannot be found, throws an [AssetNotFoundException].
-  Future<Asset> getInput(AssetId id) {
-    _timeAwaitingInputs.start();
-    _pendingSecondaryInputs[id] = _pendingSecondaryInputs.containsKey(id)
-        ? _pendingSecondaryInputs[id] + 1
-        : 1;
-    return phase.previous.getOutput(id).then((node) {
-      // Throw if the input isn't found. This ensures the transformer's apply
-      // is exited. We'll then catch this and report it through the proper
-      // results stream.
-      if (node == null) {
-        _missingInputs.add(id);
-
-        // If this id is for an asset in another package, subscribe to that
-        // package's asset cascade so when it starts emitting the id we know to
-        // re-run the transformer.
-        if (id.package != phase.cascade.package) {
-          var stream = phase.cascade.graph.onAssetFor(id.package);
-          if (stream != null) {
-            _missingExternalInputSubscriptions.putIfAbsent(id.package, () {
-              return stream.listen((node) {
-                if (!_missingInputs.contains(node.id)) return;
-                if (_forced) node.force();
-                _dirty();
-              });
-            });
-          }
-        }
-
-        throw new AssetNotFoundException(id);
-      }
-
-      _secondarySubscriptions.putIfAbsent(node.id, () {
-        return node.onStateChange.listen((_) => _dirty());
-      });
-
-      return node.asset;
-    }).whenComplete(() {
-      assert(_pendingSecondaryInputs.containsKey(id));
-      if (_pendingSecondaryInputs[id] == 1) {
-        _pendingSecondaryInputs.remove(id);
-      } else {
-        _pendingSecondaryInputs[id]--;
-      }
-      if (_pendingSecondaryInputs.isEmpty) _timeAwaitingInputs.stop();
-    });
-  }
-
-  /// Run [AggregateTransformer.apply].
-  ///
-  /// Returns whether or not an error occurred while running the transformer.
-  Future<bool> _runApply() {
-    var controller = new AggregateTransformController(this);
-    _applyController = controller;
-    _streams.onLogPool.add(controller.onLog);
-    for (var primary in _primaries) {
-      if (!primary.state.isAvailable) continue;
-      controller.addInput(primary.asset);
-    }
-    _maybeFinishApplyController();
-
-    var transformCounterTimer;
-
-    return syncFuture(() {
-      _timeInTransformer.reset();
-      _timeAwaitingInputs.reset();
-      _timeInTransformer.start();
-
-      transformCounterTimer = new Timer.periodic(_applyLogDuration, (_) {
-        if (_streams.onLogController.isClosed ||
-            !_timeInTransformer.isRunning) {
-          return;
-        }
-
-        var message = new StringBuffer("Not yet complete after "
-            "${niceDuration(_timeInTransformer.elapsed)}");
-        if (_pendingSecondaryInputs.isNotEmpty) {
-          message.write(", waiting on input(s) "
-              "${_pendingSecondaryInputs.keys.join(", ")}");
-        }
-        _streams.onLogController.add(new LogEntry(
-              info,
-              info.primaryId,
-              LogLevel.FINE,
-              message.toString(),
-              null));
-      });
-
-      return transformer.apply(controller.transform);
-    }).whenComplete(() {
-      transformCounterTimer.cancel();
-      _timeInTransformer.stop();
-      _timeAwaitingInputs.stop();
-
-      // Cancel the controller here even if `apply` wasn't interrupted. Since
-      // the apply is finished, we want to close out the controller's streams.
-      controller.cancel();
-      _applyController = null;
-    }).then((_) {
-      assert(_state != _State.DECLARED);
-      assert(_state != _State.DECLARING);
-      assert(_state != _State.APPLIED);
-
-      if (!_forced && _primaries.any((node) => !node.state.isAvailable)) {
-        _state = _State.DECLARED;
-        _streams.changeStatus(NodeStatus.IDLE);
-        return false;
-      }
-
-      if (_isRemoved) return false;
-      if (_state == _State.NEEDS_APPLY) return false;
-      if (_state == _State.NEEDS_DECLARE) return false;
-      if (controller.loggedError) return true;
-
-      // If the transformer took long enough, log its duration in fine output.
-      // That way it's not always visible, but users running with "pub serve
-      // --verbose" can see it.
-      var ranLong = _timeInTransformer.elapsed > new Duration(seconds: 1);
-      var ranLongLocally =
-          _timeInTransformer.elapsed - _timeAwaitingInputs.elapsed >
-            new Duration(milliseconds: 200);
-
-      // Report the transformer's timing information if it spent more than 0.2s
-      // doing things other than waiting for its secondary inputs or if it spent
-      // more than 1s in total.
-      if (ranLongLocally || ranLong) {
-        _streams.onLogController.add(new LogEntry(
-            info, info.primaryId, LogLevel.FINE,
-            "Took ${niceDuration(_timeInTransformer.elapsed)} "
-              "(${niceDuration(_timeAwaitingInputs.elapsed)} awaiting "
-              "secondary inputs).",
-            null));
-      }
-
-      _handleApplyResults(controller);
-      return false;
-    }).catchError((error, stackTrace) {
-      // If the transform became dirty while processing, ignore any errors from
-      // it.
-      if (_state == _State.NEEDS_APPLY || _isRemoved) return false;
-
-      // Catch all transformer errors and pipe them to the results stream. This
-      // is so a broken transformer doesn't take down the whole graph.
-      phase.cascade.reportError(_wrapException(error, stackTrace));
-      return true;
-    });
-  }
-
-  /// Handle the results of running [Transformer.apply].
-  ///
-  /// [controller] should be the controller for the [AggegateTransform] passed
-  /// to [AggregateTransformer.apply].
-  void _handleApplyResults(AggregateTransformController controller) {
-    _consumedPrimaries = controller.consumedPrimaries;
-
-    var newOutputs = controller.outputs;
-    // Any ids that are for a different package are invalid.
-    var invalidIds = newOutputs
-        .map((asset) => asset.id)
-        .where((id) => id.package != phase.cascade.package)
-        .toSet();
-    for (var id in invalidIds) {
-      newOutputs.removeId(id);
-      // TODO(nweiz): report this as a warning rather than a failing error.
-      phase.cascade.reportError(new InvalidOutputException(info, id));
-    }
-
-    // Remove outputs that used to exist but don't anymore.
-    for (var id in _outputControllers.keys.toList()) {
-      if (newOutputs.containsId(id)) continue;
-      _outputControllers.remove(id).setRemoved();
-    }
-
-    // Emit or stop emitting pass-through assets between removing and adding
-    // outputs to ensure there are no collisions.
-    for (var id in _primaries.map((node) => node.id)) {
-      if (_consumedPrimaries.contains(id) || newOutputs.containsId(id)) {
-        _consumePrimary(id);
-      } else {
-        _passThrough(id);
-      }
-    }
-
-    // Store any new outputs or new contents for existing outputs.
-    for (var asset in newOutputs) {
-      var controller = _outputControllers[asset.id];
-      if (controller != null) {
-        controller.setAvailable(asset);
-      } else {
-        var controller = new AssetNodeController.available(asset, this);
-        _outputControllers[asset.id] = controller;
-        _streams.onAssetController.add(controller.node);
-      }
-    }
-  }
-
-  /// Cancels all subscriptions to secondary input nodes and other cascades.
-  void _clearSecondarySubscriptions() {
-    _missingInputs.clear();
-    for (var subscription in _secondarySubscriptions.values) {
-      subscription.cancel();
-    }
-    for (var subscription in _missingExternalInputSubscriptions.values) {
-      subscription.cancel();
-    }
-    _secondarySubscriptions.clear();
-    _missingExternalInputSubscriptions.clear();
-  }
-
-  /// Removes all output assets.
-  void _clearOutputs() {
-    // Remove all the previously-emitted assets.
-    for (var controller in _outputControllers.values) {
-      controller.setRemoved();
-    }
-    _outputControllers.clear();
-  }
-
-  /// Emit the pass-through node for the primary input [id] if it's not being
-  /// emitted already.
-  void _passThrough(AssetId id) {
-    assert(!_outputControllers.containsKey(id));
-
-    if (_consumedPrimaries.contains(id)) return;
-    var controller = _passThroughControllers[id];
-    var primary = _primaries[id];
-    if (controller == null) {
-      controller = new AssetNodeController.from(primary);
-      _passThroughControllers[id] = controller;
-      _streams.onAssetController.add(controller.node);
-    } else if (primary.state.isDirty) {
-      controller.setDirty();
-    } else if (!controller.node.state.isAvailable) {
-      controller.setAvailable(primary.asset);
-    }
-  }
-
-  /// Stops emitting the pass-through node for the primary input [id] if it's
-  /// being emitted.
-  void _consumePrimary(AssetId id) {
-    var controller = _passThroughControllers.remove(id);
-    if (controller == null) return;
-    controller.setRemoved();
-  }
-
-  /// If `declareOutputs` is running and all previous phases have declared their
-  /// outputs, mark [_declareController] as done.
-  void _maybeFinishDeclareController() {
-    if (_declareController == null) return;
-    if (classifier.isClassifying) return;
-    if (phase.previous.status == NodeStatus.RUNNING) return;
-    _declareController.done();
-  }
-
-  /// If `apply` is running, all previous phases have declared their outputs,
-  /// and all primary inputs are available and thus have been passed to the
-  /// transformer, mark [_applyController] as done.
-  void _maybeFinishApplyController() {
-    if (_applyController == null) return;
-    if (classifier.isClassifying) return;
-    if (_primaries.any((input) => !input.state.isAvailable)) return;
-    if (phase.previous.status == NodeStatus.RUNNING) return;
-    _applyController.done();
-  }
-
-  BarbackException _wrapException(error, StackTrace stackTrace) {
-    if (error is! AssetNotFoundException) {
-      return new TransformerException(info, error, stackTrace);
-    } else {
-      return new MissingInputException(info, error.id);
-    }
-  }
-
-  String toString() =>
-      "transform node in $_location for $transformer on ${info.primaryId} "
-      "($_state, $status, ${_forced ? '' : 'un'}forced)";
-}
-
-/// The enum of states that [TransformNode] can be in.
-class _State {
-  /// The transform is running [DeclaringAggregateTransformer.declareOutputs].
-  ///
-  /// If the set of primary inputs changes while in this state, it will
-  /// transition to [NEEDS_DECLARE]. If the [TransformNode] is still in this
-  /// state when `declareOutputs` finishes running, it will transition to
-  /// [APPLYING] if the transform is non-lazy and all of its primary inputs are
-  /// available, and [DECLARED] otherwise.
-  ///
-  /// Non-declaring transformers will transition out of this state and into
-  /// [APPLYING] immediately.
-  static const DECLARING = const _State._("declaring outputs");
-
-  /// The transform is running [AggregateTransformer.declareOutputs] or
-  /// [AggregateTransform.apply], but a primary input was added or removed after
-  /// it started, so it will need to re-run `declareOutputs`.
-  ///
-  /// The [TransformNode] will transition to [DECLARING] once `declareOutputs`
-  /// or `apply` finishes running.
-  static const NEEDS_DECLARE = const _State._("needs declare");
-
-  /// The transform is deferred and has run
-  /// [DeclaringAggregateTransformer.declareOutputs] but hasn't yet been forced.
-  ///
-  /// The [TransformNode] will transition to [APPLYING] when one of the outputs
-  /// has been forced or if the transformer is non-lazy and all of its primary
-  /// inputs become available.
-  static const DECLARED = const _State._("declared");
-
-  /// The transform is running [AggregateTransformer.apply].
-  ///
-  /// If an input's contents change or a secondary input is added or removed
-  /// while in this state, the [TransformNode] will transition to [NEEDS_APPLY].
-  /// If a primary input is added or removed, it will transition to
-  /// [NEEDS_DECLARE]. If it's still in this state when `apply` finishes
-  /// running, it will transition to [APPLIED].
-  static const APPLYING = const _State._("applying");
-
-  /// The transform is running [AggregateTransformer.apply], but an input's
-  /// contents changed or a secondary input was added or removed after it
-  /// started, so it will need to re-run `apply`.
-  ///
-  /// If a primary input is added or removed while in this state, the
-  /// [TranformNode] will transition to [NEEDS_DECLARE]. If it's still in this
-  /// state when `apply` finishes running, it will transition to [APPLYING].
-  static const NEEDS_APPLY = const _State._("needs apply");
-
-  /// The transform has finished running [AggregateTransformer.apply], whether
-  /// or not it emitted an error.
-  ///
-  /// If an input's contents change or a secondary input is added or removed,
-  /// the [TransformNode] will transition to [DECLARED] if the transform is
-  /// declaring and [APPLYING] otherwise. If a primary input is added or
-  /// removed, this will transition to [DECLARING].
-  static const APPLIED = const _State._("applied");
-
-  final String name;
-
-  const _State._(this.name);
-
-  String toString() => name;
-}