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barback/lib/src/graph/phase.dart

Index: barback/lib/src/graph/phase.dart
diff --git a/barback/lib/src/graph/phase.dart b/barback/lib/src/graph/phase.dart
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index 4bfc5e19fd1a74decd504ee8e1f1b8aa3a9a0a19..0000000000000000000000000000000000000000
--- a/barback/lib/src/graph/phase.dart
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-// 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;
-
-import 'dart:async';
-
-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_transformer.dart';
-import '../transformer/transformer.dart';
-import '../transformer/transformer_group.dart';
-import '../utils.dart';
-import '../utils/multiset.dart';
-import 'asset_cascade.dart';
-import 'group_runner.dart';
-import 'node_status.dart';
-import 'node_streams.dart';
-import 'phase_forwarder.dart';
-import 'phase_output.dart';
-import 'transformer_classifier.dart';
-
-/// One phase in the ordered series of transformations in an [AssetCascade].
-///
-/// Each phase can access outputs from previous phases and can in turn pass
-/// outputs to later phases. Phases are processed strictly serially. All
-/// transforms in a phase will be complete before moving on to the next phase.
-/// Within a single phase, all transforms will be run in parallel.
-///
-/// Building can be interrupted between phases. For example, a source is added
-/// which starts the background process. Sometime during, say, phase 2 (which
-/// is running asynchronously) that source is modified. When the process queue
-/// goes to advance to phase 3, it will see that modification and start the
-/// waterfall from the beginning again.
-class Phase {
-  /// The cascade that owns this phase.
-  final AssetCascade cascade;
-
-  /// A string describing the location of [this] in the transformer graph.
-  final String _location;
-
-  /// The index of [this] in its parent cascade or group.
-  final int _index;
-
-  /// The groups for this phase.
-  final _groups = new Map<TransformerGroup, GroupRunner>();
-
-  /// The inputs for this phase.
-  ///
-  /// For the first phase, these will be the source assets. For all other
-  /// phases, they will be the outputs from the previous phase.
-  final _inputs = new AssetNodeSet();
-
-  /// The transformer classifiers for this phase.
-  ///
-  /// The keys can be either [Transformer]s or [AggregateTransformer]s.
-  final _classifiers = new Map<dynamic, TransformerClassifier>();
-
-  /// The forwarders for this phase.
-  final _forwarders = new Map<AssetId, PhaseForwarder>();
-
-  /// The outputs for this phase.
-  final _outputs = new Map<AssetId, PhaseOutput>();
-
-  /// The set of all [AssetNode.origin] properties of the input assets for this
-  /// phase.
-  ///
-  /// This is used to determine which assets have been passed unmodified through
-  /// [_classifiers] or [_groups]. It's possible that a given asset was consumed
-  /// by a group and not an individual transformer, and so shouldn't be
-  /// forwarded through the phase as a whole.
-  ///
-  /// In order to detect whether an output has been forwarded through a group or
-  /// a classifier, we must be able to distinguish it from other outputs with
-  /// the same id. To do so, we check if its origin is in [_inputOrigins]. If
-  /// so, it's been forwarded unmodified.
-  final _inputOrigins = new Multiset<AssetNode>();
-
-  /// The streams exposed by this phase.
-  final _streams = new NodeStreams();
-  Stream<NodeStatus> get onStatusChange => _streams.onStatusChange;
-  Stream<AssetNode> get onAsset => _streams.onAsset;
-  Stream<LogEntry> get onLog => _streams.onLog;
-
-  /// How far along [this] is in processing its assets.
-  NodeStatus get status {
-    // Before any transformers are added, the phase should be dirty if and only
-    // if any input is dirty.
-    if (_classifiers.isEmpty && _groups.isEmpty && previous == null) {
-      return _inputs.any((input) => input.state.isDirty) ?
-          NodeStatus.RUNNING : NodeStatus.IDLE;
-    }
-
-    var classifierStatus = NodeStatus.dirtiest(
-        _classifiers.values.map((classifier) => classifier.status));
-    var groupStatus = NodeStatus.dirtiest(
-        _groups.values.map((group) => group.status));
-    return (previous == null ? NodeStatus.IDLE : previous.status)
-        .dirtier(classifierStatus)
-        .dirtier(groupStatus);
-  }
-
-  /// The previous phase in the cascade, or null if this is the first phase.
-  final Phase previous;
-
-  /// The subscription to [previous]'s [onStatusChange] stream.
-  StreamSubscription _previousStatusSubscription;
-
-  /// The subscription to [previous]'s [onAsset] stream.
-  StreamSubscription<AssetNode> _previousOnAssetSubscription;
-
-  final _inputSubscriptions = new Set<StreamSubscription>();
-
-  /// A map of asset ids to completers for [getInput] requests.
-  ///
-  /// If an asset node is requested before it's available, we put a completer in
-  /// this map to wait for the asset to be generated. If it's not generated, the
-  /// completer should complete to `null`.
-  final _pendingOutputRequests = new Map<AssetId, Completer<AssetNode>>();
-
-  /// Returns all currently-available output assets for this phase.
-  Set<AssetNode> get availableOutputs {
-    return _outputs.values
-        .map((output) => output.output)
-        .where((node) => node.state.isAvailable)
-        .toSet();
-  }
-
-  // TODO(nweiz): Rather than passing the cascade and the phase everywhere,
-  // create an interface that just exposes [getInput]. Emit errors via
-  // [AssetNode]s.
-  Phase(AssetCascade cascade, String location)
-      : this._(cascade, location, 0);
-
-  Phase._(this.cascade, this._location, this._index, [this.previous]) {
-    if (previous != null) {
-      _previousOnAssetSubscription = previous.onAsset.listen(addInput);
-      _previousStatusSubscription = previous.onStatusChange
-          .listen((_) => _streams.changeStatus(status));
-    }
-
-    onStatusChange.listen((status) {
-      if (status == NodeStatus.RUNNING) return;
-
-      // All the previous phases have finished declaring or producing their
-      // outputs. If anyone's still waiting for outputs, cut off the wait; we
-      // won't be generating them, at least until a source asset changes.
-      for (var completer in _pendingOutputRequests.values) {
-        completer.complete(null);
-      }
-      _pendingOutputRequests.clear();
-    });
-  }
-
-  /// Adds a new asset as an input for this phase.
-  ///
-  /// [node] doesn't have to be [AssetState.AVAILABLE]. Once it is, the phase
-  /// will automatically begin determining which transforms can consume it as a
-  /// primary input. The transforms themselves won't be applied until [process]
-  /// is called, however.
-  ///
-  /// This should only be used for brand-new assets or assets that have been
-  /// removed and re-created. The phase will automatically handle updated assets
-  /// using the [AssetNode.onStateChange] stream.
-  void addInput(AssetNode node) {
-    // Each group is one channel along which an asset may be forwarded, as is
-    // each transformer.
-    var forwarder = new PhaseForwarder(
-        node, _classifiers.length, _groups.length);
-    _forwarders[node.id] = forwarder;
-    forwarder.onAsset.listen(_handleOutputWithoutForwarder);
-    if (forwarder.output != null) {
-      _handleOutputWithoutForwarder(forwarder.output);
-    }
-
-    _inputOrigins.add(node.origin);
-    _inputs.add(node);
-    _inputSubscriptions.add(node.onStateChange.listen((state) {
-      if (state.isRemoved) {
-        _inputOrigins.remove(node.origin);
-        _forwarders.remove(node.id).remove();
-      }
-      _streams.changeStatus(status);
-    }));
-
-    for (var classifier in _classifiers.values) {
-      classifier.addInput(node);
-    }
-  }
-
-  // TODO(nweiz): If the output is available when this is called, it's
-  // theoretically possible for it to become unavailable between the call and
-  // the return. If it does so, it won't trigger the rebuilding process. To
-  // avoid this, we should have this and the methods it calls take explicit
-  // callbacks, as in [AssetNode.whenAvailable].
-  /// Gets the asset node for an output [id].
-  ///
-  /// If [id] is for a generated or transformed asset, this will wait until it
-  /// has been created and return it. This means that the returned asset will
-  /// always be [AssetState.AVAILABLE].
-  /// 
-  /// If the output cannot be found, returns null.
-  Future<AssetNode> getOutput(AssetId id) {
-    return syncFuture(() {
-      if (id.package != cascade.package) return cascade.graph.getAssetNode(id);
-      if (_outputs.containsKey(id)) {
-        var output = _outputs[id].output;
-        // If the requested output is available, we can just return it.
-        if (output.state.isAvailable) return output;
-
-        // If the requested output exists but isn't yet available, wait to see
-        // if it becomes available. If it's removed before becoming available,
-        // try again, since it could be generated again.
-        output.force();
-        return output.whenAvailable((_) {
-          return output;
-        }).catchError((error) {
-          if (error is! AssetNotFoundException) throw error;
-          return getOutput(id);
-        });
-      }
-
-      // If this phase and the previous phases are fully declared or done, the
-      // requested output won't be generated and we can safely return null.
-      if (status != NodeStatus.RUNNING) return null;
-
-      // Otherwise, store a completer for the asset node. If it's generated in
-      // the future, we'll complete this completer.
-      var completer = _pendingOutputRequests.putIfAbsent(id,
-          () => new Completer.sync());
-      return completer.future;
-    });
-  }
-
-  /// Set this phase's transformers to [transformers].
-  void updateTransformers(Iterable transformers) {
-    var newTransformers = transformers
-        .where((op) => op is Transformer || op is AggregateTransformer)
-        .toSet();
-    var oldTransformers = _classifiers.keys.toSet();
-    for (var removed in oldTransformers.difference(newTransformers)) {
-      _classifiers.remove(removed).remove();
-    }
-
-    for (var transformer in newTransformers.difference(oldTransformers)) {
-      var classifier = new TransformerClassifier(
-          this, transformer, "$_location.$_index");
-      _classifiers[transformer] = classifier;
-      classifier.onAsset.listen(_handleOutput);
-      _streams.onLogPool.add(classifier.onLog);
-      classifier.onStatusChange.listen((_) => _streams.changeStatus(status));
-      for (var input in _inputs) {
-        classifier.addInput(input);
-      }
-    }
-
-    var newGroups = transformers.where((op) => op is TransformerGroup)
-        .toSet();
-    var oldGroups = _groups.keys.toSet();
-    for (var removed in oldGroups.difference(newGroups)) {
-      _groups.remove(removed).remove();
-    }
-
-    for (var added in newGroups.difference(oldGroups)) {
-      var runner = new GroupRunner(previous, added, "$_location.$_index");
-      _groups[added] = runner;
-      runner.onAsset.listen(_handleOutput);
-      _streams.onLogPool.add(runner.onLog);
-      runner.onStatusChange.listen((_) => _streams.changeStatus(status));
-    }
-
-    for (var forwarder in _forwarders.values) {
-      forwarder.updateTransformers(_classifiers.length, _groups.length);
-    }
-
-    _streams.changeStatus(status);
-  }
-
-  /// Force all [LazyTransformer]s' transforms in this phase to begin producing
-  /// concrete assets.
-  void forceAllTransforms() {
-    for (var classifier in _classifiers.values) {
-      classifier.forceAllTransforms();
-    }
-
-    for (var group in _groups.values) {
-      group.forceAllTransforms();
-    }
-  }
-
-  /// Add a new phase after this one.
-  ///
-  /// The new phase will have a location annotation describing its place in the
-  /// package graph. By default, this annotation will describe it as being
-  /// directly after [this]. If [location] is passed, though, it's described as
-  /// being the first phase in that location.
-  Phase addPhase([String location]) {
-    var index = 0;
-    if (location == null) {
-      location = _location;
-      index = _index + 1;
-    }
-
-    var next = new Phase._(cascade, location, index, this);
-    for (var output in _outputs.values.toList()) {
-      // Remove [output]'s listeners because now they should get the asset from
-      // [next], rather than this phase. Any transforms consuming [output] will
-      // be re-run and will consume the output from the new final phase.
-      output.removeListeners();
-    }
-    return next;
-  }
-
-  /// Mark this phase as removed.
-  ///
-  /// This will remove all the phase's outputs.
-  void remove() {
-    for (var classifier in _classifiers.values.toList()) {
-      classifier.remove();
-    }
-    for (var group in _groups.values) {
-      group.remove();
-    }
-    _streams.close();
-    for (var subscription in _inputSubscriptions) {
-      subscription.cancel();
-    }
-    if (_previousStatusSubscription != null) {
-      _previousStatusSubscription.cancel();
-    }
-    if (_previousOnAssetSubscription != null) {
-      _previousOnAssetSubscription.cancel();
-    }
-  }
-
-  /// Add [asset] as an output of this phase.
-  void _handleOutput(AssetNode asset) {
-    if (_inputOrigins.contains(asset.origin)) {
-      _forwarders[asset.id].addIntermediateAsset(asset);
-    } else {
-      _handleOutputWithoutForwarder(asset);
-    }
-  }
-
-  /// Add [asset] as an output of this phase without checking if it's a
-  /// forwarded asset.
-  void _handleOutputWithoutForwarder(AssetNode asset) {
-    if (_outputs.containsKey(asset.id)) {
-      _outputs[asset.id].add(asset);
-    } else {
-      _outputs[asset.id] = new PhaseOutput(this, asset, "$_location.$_index");
-      _outputs[asset.id].onAsset.listen(_emit,
-          onDone: () => _outputs.remove(asset.id));
-      _emit(_outputs[asset.id].output);
-    }
-
-    var exception = _outputs[asset.id].collisionException;
-    if (exception != null) cascade.reportError(exception);
-  }
-
-  /// Emit [asset] as an output of this phase.
-  ///
-  /// This should be called after [_handleOutput], so that collisions are
-  /// resolved.
-  void _emit(AssetNode asset) {
-    _streams.onAssetController.add(asset);
-    _providePendingAsset(asset);
-  }
-
-  /// Provide an asset to a pending [getOutput] call.
-  void _providePendingAsset(AssetNode asset) {
-    // If anyone's waiting for this asset, provide it to them.
-    var request = _pendingOutputRequests.remove(asset.id);
-    if (request == null) return;
-
-    if (asset.state.isAvailable) {
-      request.complete(asset);
-      return;
-    }
-
-    // A lazy asset may be emitted while still dirty. If so, we wait until it's
-    // either available or removed before trying again to access it.
-    assert(asset.state.isDirty);
-    asset.force();
-    asset.whenStateChanges().then((state) {
-      if (state.isRemoved) return getOutput(asset.id);
-      return asset;
-    }).then(request.complete).catchError(request.completeError);
-  }
-
-  String toString() => "phase $_location.$_index";
-}