Index: mojo/public/dart/third_party/barback/lib/src/transformer/declaring_aggregate_transform.dart |
diff --git a/mojo/public/dart/third_party/barback/lib/src/transformer/declaring_aggregate_transform.dart b/mojo/public/dart/third_party/barback/lib/src/transformer/declaring_aggregate_transform.dart |
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+// Copyright (c) 2014, 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.transformer.declaring_aggregate_transform; |
+ |
+import 'dart:async'; |
+ |
+import '../asset/asset_id.dart'; |
+import '../graph/transform_node.dart'; |
+import '../utils.dart'; |
+import 'base_transform.dart'; |
+ |
+/// A transform for [DeclaringAggregateTransformer]s that allows them to declare |
+/// the ids of the outputs they'll generate without generating the concrete |
+/// bodies of those outputs. |
+class DeclaringAggregateTransform extends BaseTransform { |
+ /// The set of output ids declared by the transformer. |
+ final _outputIds = new Set<AssetId>(); |
+ |
+ /// The transform key. |
+ /// |
+ /// This is the key returned by [AggregateTransformer.classifyPrimary] for all |
+ /// the assets in this transform. |
+ final String key; |
+ |
+ /// The package in which this transform is running. |
+ final String package; |
+ |
+ /// The stream of primary input ids that have been aggregated for this |
+ /// transform. |
+ /// |
+ /// This is exposed as a stream so that the transformer can start working |
+ /// before all its input ids are available. The stream is closed not just when |
+ /// all inputs are provided, but when barback is confident no more inputs will |
+ /// be forthcoming. |
+ /// |
+ /// A transformer may complete its `declareOutputs` method before this stream |
+ /// is closed. For example, it may know that each key will only have two |
+ /// inputs associated with it, and so use `transform.primaryIds.take(2)` to |
+ /// access only those inputs' ids. |
+ Stream<AssetId> get primaryIds => _primaryIds; |
+ Stream<AssetId> _primaryIds; |
+ |
+ /// The controller for [primaryIds]. |
+ /// |
+ /// This is a broadcast controller so that the transform can keep |
+ /// [_emittedPrimaryIds] up to date. |
+ final _idController = new StreamController<AssetId>.broadcast(); |
+ |
+ /// The set of all primary input ids that have been emitted by [primaryIds]. |
+ final _emittedPrimaryIds = new Set<AssetId>(); |
+ |
+ DeclaringAggregateTransform._(TransformNode node) |
+ : key = node.key, |
+ package = node.phase.cascade.package, |
+ super(node) { |
+ _idController.stream.listen(_emittedPrimaryIds.add); |
+ // [primaryIds] should be a non-broadcast stream. |
+ _primaryIds = broadcastToSingleSubscription(_idController.stream); |
+ } |
+ |
+ /// Stores [id] as the id of an output that will be created by this |
+ /// transformation when it's run. |
+ /// |
+ /// A transformation can declare as many assets as it wants. If |
+ /// [DeclaringTransformer.declareOutputs] declares a given asset id for a |
+ /// given input, [Transformer.apply] should emit the corresponding asset as |
+ /// well. |
+ void declareOutput(AssetId id) { |
+ // TODO(nweiz): This should immediately throw if an output with that ID |
+ // has already been declared by this transformer. |
+ _outputIds.add(id); |
+ } |
+ |
+ void consumePrimary(AssetId id) { |
+ if (!_emittedPrimaryIds.contains(id)) { |
+ throw new StateError( |
+ "$id can't be consumed because it's not a primary input."); |
+ } |
+ |
+ super.consumePrimary(id); |
+ } |
+} |
+ |
+/// The controller for [DeclaringAggregateTransform]. |
+class DeclaringAggregateTransformController extends BaseTransformController { |
+ DeclaringAggregateTransform get transform => super.transform; |
+ |
+ /// The set of ids that the transformer declares it will emit. |
+ Set<AssetId> get outputIds => transform._outputIds; |
+ |
+ bool get isDone => transform._idController.isClosed; |
+ |
+ DeclaringAggregateTransformController(TransformNode node) |
+ : super(new DeclaringAggregateTransform._(node)); |
+ |
+ /// Adds a primary input id to the [DeclaringAggregateTransform.primaryIds] |
+ /// stream. |
+ void addId(AssetId id) => transform._idController.add(id); |
+ |
+ void done() { |
+ transform._idController.close(); |
+ } |
+} |