Add support for transformer clusters to barback.

pkg/barback/lib/src/phase.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.phase;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'asset_cascade.dart';
 import 'asset_id.dart';
 import 'asset_node.dart';
 import 'asset_set.dart';
+import 'group_runner.dart';
 import 'errors.dart';
+import 'phase_forwarder.dart';
 import 'phase_input.dart';
 import 'phase_output.dart';
 import 'stream_pool.dart';
 import 'transformer.dart';
+import 'transformer_group.dart';
 import 'utils.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;
 
   /// The transformers that can access [inputs].
   ///
   /// Their outputs will be available to the next phase.
   final Set<Transformer> _transformers;
 
+  /// 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 Map<AssetId, PhaseInput>();
 
+  /// The forwarders for this phase.
+  final _forwarders = new Map<AssetId, PhaseForwarder>();
+
   /// The outputs for this phase.
   final _outputs = new Map<AssetId, PhaseOutput>();
 
+  // TODO(nweiz): Don't re-calculate this on the fly all the time.
+  /// 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
+  /// [_inputs] or [_groups]. Each input asset has a PhaseInput in [_inputs]. If
+  /// that input isn't consumed by any transformers, it will be forwarded
+  /// through the PhaseInput. However, it's possible that it was consumed by a
+  /// group, 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 PhaseInput, 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.
+  Set<AssetNode> get _inputOrigins =>
+    _inputs.values.map((input) => input.input.origin).toSet();
+
   /// A stream that emits an event whenever this phase becomes dirty and needs
   /// to be run.
   ///
   /// This may emit events when the phase was already dirty or while processing
   /// transforms. Events are emitted synchronously to ensure that the dirty
   /// state is thoroughly propagated as soon as any assets are changed.
   Stream get onDirty => _onDirtyPool.stream;
   final _onDirtyPool = new StreamPool.broadcast();
 
   /// A controller whose stream feeds into [_onDirtyPool].
   ///
   /// This is used whenever an input is added or transforms are changed.
   final _onDirtyController = new StreamController.broadcast(sync: true);
 
+  /// Whether this phase is dirty and needs to be run.
+  bool get isDirty => _inputs.values.any((input) => input.isDirty) ||
+      _groups.values.any((group) => group.isDirty);
+
   /// The phase after this one.
   ///
   /// Outputs from this phase will be passed to it.
   Phase get next => _next;
   Phase _next;
 
   /// Returns all currently-available output assets for this phase.
-  AssetSet get availableOutputs {
-    return new AssetSet.from(_outputs.values
+  Set<AssetNode> get availableOutputs {
+    return _outputs.values
         .map((output) => output.output)
         .where((node) => node.state.isAvailable)
-        .map((node) => node.asset));
+        .toSet();
   }
 
-  Phase(this.cascade, Iterable<Transformer> transformers)
-      : _transformers = transformers.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(this.cascade, Iterable transformers)
+      : _transformers = transformers.where((op) => op is Transformer).toSet() {
     _onDirtyPool.add(_onDirtyController.stream);
+
+    for (var group in transformers.where((op) => op is TransformerGroup)) {
+      _groups[group] = new GroupRunner(cascade, group);
+      _onDirtyPool.add(_groups[group].onDirty);
+    }
   }
 
   /// 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) {
     if (_inputs.containsKey(node.id)) _inputs[node.id].remove();
 
+    // Each group is one channel along which an asset may be forwarded. Then
+    // there's one additional channel for the non-grouped transformers.
+    var forwarder = new PhaseForwarder(_groups.length + 1);
+    _forwarders[node.id] = forwarder;
+    forwarder.onForwarding.listen((asset) {
+      _addOutput(asset);
+
+      var exception = _outputs[asset.id].collisionException;
+      if (exception != null) cascade.reportError(exception);
+    });
+
     var input = new PhaseInput(this, node, _transformers);
     _inputs[node.id] = input;
-    input.input.whenRemoved.then((_) => _inputs.remove(node.id));
+    input.input.whenRemoved.then((_) {
+      _inputs.remove(node.id);
+      _forwarders.remove(node.id).remove();
+    });
     _onDirtyPool.add(input.onDirty);
     _onDirtyController.add(null);
+
+    for (var group in _groups.values) {
+      group.addInput(node);
+    }
   }
 
   /// Gets the asset node for an input [id].
   ///
   /// If an input with that ID cannot be found, returns null.
   Future<AssetNode> getInput(AssetId id) {
     return newFuture(() {
       if (id.package != cascade.package) return cascade.graph.getAssetNode(id);
       if (_inputs.containsKey(id)) return _inputs[id].input;
       return null;
     });
   }
 
   /// Gets the asset node for an output [id].
   ///
   /// If an output with that ID cannot be found, returns null.
   Future<AssetNode> getOutput(AssetId id) {
     return newFuture(() {
       if (id.package != cascade.package) return cascade.graph.getAssetNode(id);
       if (!_outputs.containsKey(id)) return null;
       return _outputs[id].output;
     });
   }
 
   /// Set this phase's transformers to [transformers].
-  void updateTransformers(Iterable<Transformer> transformers) {
+  void updateTransformers(Iterable transformers) {
     _onDirtyController.add(null);
+
+    var actualTransformers = transformers.where((op) => op is Transformer);
     _transformers.clear();
-    _transformers.addAll(transformers);
+    _transformers.addAll(actualTransformers);
     for (var input in _inputs.values) {
-      input.updateTransformers(_transformers);
+      input.updateTransformers(actualTransformers);
+    }
+
+    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(cascade, added);
+      _groups[added] = runner;
+      _onDirtyPool.add(runner.onDirty);
+      for (var input in _inputs.values) {
+        runner.addInput(input.input);
+      }
+    }
+
+    for (var forwarder in _forwarders.values) {
+      forwarder.numChannels = _groups.length + 1;
     }
   }
 
   /// Add a new phase after this one with [transformers].
   ///
   /// This may only be called on a phase with no phase following it.
-  Phase addPhase(Iterable<Transformer> transformers) {
+  Phase addPhase(Iterable transformers) {
     assert(_next == null);
     _next = new Phase(cascade, transformers);
     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();
 
       // Removing [output]'s listeners will cause it to be removed from
       // [_outputs], so we have to put it back.
       _outputs[output.output.id] = output;
       output.output.whenRemoved.then((_) => _outputs.remove(output.output.id));
       _next.addInput(output.output);
     }
     return _next;
   }
 
   /// Mark this phase as removed.
   ///
   /// This will remove all the phase's outputs and all following phases.
   void remove() {
     removeFollowing();
     for (var input in _inputs.values.toList()) {
       input.remove();
     }
+    for (var group in _groups.values) {
+      group.remove();
+    }
     _onDirtyPool.close();
   }
 
   /// Remove all phases after this one.
   void removeFollowing() {
     if (_next == null) return;
     _next.remove();
     _next = null;
   }
 
   /// Processes this phase.
   ///
   /// Returns a future that completes when processing is done. If there is
   /// nothing to process, returns `null`.
   Future process() {
-    if (!_inputs.values.any((input) => input.isDirty)) return null;
+    if (!isDirty) return null;
 
     var outputIds = new Set<AssetId>();
-    return Future.wait(_inputs.values.map((input) {
+    void _handleOutputs(Set<AssetNode> outputs) {
+      for (var asset in outputs) {
+        if (_inputOrigins.contains(asset.origin)) {
+          _forwarders[asset.id].addIntermediateAsset(asset);
+          continue;
+        }
+
+        outputIds.add(asset.id);
+        _addOutput(asset);
+      }
+    }
+
+    var outputFutures = [];
+    outputFutures.addAll(_inputs.values.map((input) {
       if (!input.isDirty) return new Future.value(new Set());
-      return input.process().then((outputs) {
-        for (var asset in outputs) {
-          outputIds.add(asset.id);
-          if (_outputs.containsKey(asset.id)) {
-            _outputs[asset.id].add(asset);
-          } else {
-            _outputs[asset.id] = new PhaseOutput(this, asset);
-            _outputs[asset.id].output.whenRemoved.then((_) {
-              _outputs.remove(asset.id);
-            });
-            if (_next != null) _next.addInput(_outputs[asset.id].output);
-          }
-        }
-      });
-    })).then((_) {
+      return input.process().then(_handleOutputs);
+    }));
+    outputFutures.addAll(_groups.values.map((input) {
+      if (!input.isDirty) return new Future.value(new Set());
+      return input.process().then(_handleOutputs);
+    }));
+
+    // TODO(nweiz): handle pass-through.
+
+    return Future.wait(outputFutures).then((_) {
       // Report collisions in a deterministic order.
       outputIds = outputIds.toList();
       outputIds.sort((a, b) => a.compareTo(b));
       for (var id in outputIds) {
         // It's possible the output was removed before other transforms in this
         // phase finished.
         if (!_outputs.containsKey(id)) continue;
         var exception = _outputs[id].collisionException;
         if (exception != null) cascade.reportError(exception);
       }
     });
   }
+
+  /// Add [asset] as an output of this phase.
+  void _addOutput(AssetNode asset) {
+    if (_outputs.containsKey(asset.id)) {
+      _outputs[asset.id].add(asset);
+    } else {
+      _outputs[asset.id] = new PhaseOutput(this, asset);
+      _outputs[asset.id].output.whenRemoved.then((_) {
+        _outputs.remove(asset.id);
+      });
+      if (_next != null) _next.addInput(_outputs[asset.id].output);
+    }
+  }
 }