| Index: mojo/public/dart/third_party/barback/lib/src/transformer/declaring_aggregate_transform.dart
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| 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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| new file mode 100644
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| index 0000000000000000000000000000000000000000..cfcb782b5d41a16b28c44e1de7f1b572477fbcfb
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| +++ b/mojo/public/dart/third_party/barback/lib/src/transformer/declaring_aggregate_transform.dart
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| @@ -0,0 +1,105 @@
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| +// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file
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| +// for details. All rights reserved. Use of this source code is governed by a
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| +// BSD-style license that can be found in the LICENSE file.
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| +
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| +library barback.transformer.declaring_aggregate_transform;
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| +
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| +import 'dart:async';
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| +
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| +import '../asset/asset_id.dart';
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| +import '../graph/transform_node.dart';
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| +import '../utils.dart';
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| +import 'base_transform.dart';
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| +
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| +/// A transform for [DeclaringAggregateTransformer]s that allows them to declare
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| +/// the ids of the outputs they'll generate without generating the concrete
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| +/// bodies of those outputs.
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| +class DeclaringAggregateTransform extends BaseTransform {
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| + /// The set of output ids declared by the transformer.
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| + final _outputIds = new Set<AssetId>();
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| +
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| + /// The transform key.
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| + ///
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| + /// This is the key returned by [AggregateTransformer.classifyPrimary] for all
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| + /// the assets in this transform.
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| + final String key;
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| +
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| + /// The package in which this transform is running.
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| + final String package;
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| +
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| + /// The stream of primary input ids that have been aggregated for this
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| + /// transform.
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| + ///
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| + /// This is exposed as a stream so that the transformer can start working
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| + /// before all its input ids are available. The stream is closed not just when
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| + /// all inputs are provided, but when barback is confident no more inputs will
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| + /// be forthcoming.
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| + ///
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| + /// A transformer may complete its `declareOutputs` method before this stream
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| + /// is closed. For example, it may know that each key will only have two
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| + /// inputs associated with it, and so use `transform.primaryIds.take(2)` to
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| + /// access only those inputs' ids.
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| + Stream<AssetId> get primaryIds => _primaryIds;
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| + Stream<AssetId> _primaryIds;
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| +
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| + /// The controller for [primaryIds].
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| + ///
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| + /// This is a broadcast controller so that the transform can keep
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| + /// [_emittedPrimaryIds] up to date.
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| + final _idController = new StreamController<AssetId>.broadcast();
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| +
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| + /// The set of all primary input ids that have been emitted by [primaryIds].
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| + final _emittedPrimaryIds = new Set<AssetId>();
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| +
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| + DeclaringAggregateTransform._(TransformNode node)
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| + : key = node.key,
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| + package = node.phase.cascade.package,
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| + super(node) {
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| + _idController.stream.listen(_emittedPrimaryIds.add);
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| + // [primaryIds] should be a non-broadcast stream.
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| + _primaryIds = broadcastToSingleSubscription(_idController.stream);
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| + }
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| +
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| + /// Stores [id] as the id of an output that will be created by this
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| + /// transformation when it's run.
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| + ///
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| + /// A transformation can declare as many assets as it wants. If
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| + /// [DeclaringTransformer.declareOutputs] declares a given asset id for a
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| + /// given input, [Transformer.apply] should emit the corresponding asset as
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| + /// well.
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| + void declareOutput(AssetId id) {
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| + // TODO(nweiz): This should immediately throw if an output with that ID
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| + // has already been declared by this transformer.
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| + _outputIds.add(id);
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| + }
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| +
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| + void consumePrimary(AssetId id) {
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| + if (!_emittedPrimaryIds.contains(id)) {
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| + throw new StateError(
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| + "$id can't be consumed because it's not a primary input.");
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| + }
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| +
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| + super.consumePrimary(id);
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| + }
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| +}
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| +
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| +/// The controller for [DeclaringAggregateTransform].
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| +class DeclaringAggregateTransformController extends BaseTransformController {
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| + DeclaringAggregateTransform get transform => super.transform;
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| +
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| + /// The set of ids that the transformer declares it will emit.
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| + Set<AssetId> get outputIds => transform._outputIds;
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| +
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| + bool get isDone => transform._idController.isClosed;
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| +
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| + DeclaringAggregateTransformController(TransformNode node)
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| + : super(new DeclaringAggregateTransform._(node));
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| +
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| + /// Adds a primary input id to the [DeclaringAggregateTransform.primaryIds]
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| + /// stream.
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| + void addId(AssetId id) => transform._idController.add(id);
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| +
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| + void done() {
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| + transform._idController.close();
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| + }
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| +}
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|