Index: mojo/public/dart/third_party/barback/lib/src/transformer/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.transform; |
+ |
+import 'dart:async'; |
+import 'dart:convert'; |
+ |
+import '../asset/asset.dart'; |
+import '../asset/asset_id.dart'; |
+import '../errors.dart'; |
+import 'aggregate_transform.dart'; |
+import 'transform_logger.dart'; |
+ |
+/// Creates a new [Transform] wrapping an [AggregateTransform]. |
+/// |
+/// Although barback internally works in terms of [AggregateTransformer]s, most |
+/// transformers only work on individual primary inputs in isolation. We want to |
+/// allow those transformers to implement the more user-friendly [Transformer] |
+/// interface which takes the more user-friendly [Transform] object. This method |
+/// wraps the more general [AggregateTransform] to return a [Transform] instead. |
+Future<Transform> newTransform(AggregateTransform aggregate) { |
+ // A wrapped [Transformer] will assign each primary input a unique transform |
+ // key, so we can safely get the first asset emitted. We don't want to wait |
+ // for the stream to close, since that requires barback to prove that no more |
+ // new assets will be generated. |
+ return aggregate.primaryInputs.first.then((primaryInput) => |
+ new Transform._(aggregate, primaryInput)); |
+} |
+ |
+/// While a [Transformer] represents a *kind* of transformation, this defines |
+/// one specific usage of it on a set of files. |
+/// |
+/// This ephemeral object exists only during an actual transform application to |
+/// facilitate communication between the [Transformer] and the code hosting |
+/// the transformation. It lets the [Transformer] access inputs and generate |
+/// outputs. |
+class Transform { |
+ /// The underlying aggregate transform. |
+ final AggregateTransform _aggregate; |
+ |
+ /// Gets the primary input asset. |
+ /// |
+ /// While a transformation can use multiple input assets, one must be a |
+ /// special "primary" asset. This will be the "entrypoint" or "main" input |
+ /// file for a transformation. |
+ /// |
+ /// For example, with a dart2js transform, the primary input would be the |
+ /// entrypoint Dart file. All of the other Dart files that that imports |
+ /// would be secondary inputs. |
+ final Asset primaryInput; |
+ |
+ /// A logger so that the [Transformer] can report build details. |
+ TransformLogger get logger => _aggregate.logger; |
+ |
+ Transform._(this._aggregate, this.primaryInput); |
+ |
+ /// Gets the asset for an input [id]. |
+ /// |
+ /// If an input with [id] cannot be found, throws an [AssetNotFoundException]. |
+ Future<Asset> getInput(AssetId id) => _aggregate.getInput(id); |
+ |
+ /// A convenience method to the contents of the input with [id] as a string. |
+ /// |
+ /// This is equivalent to calling [getInput] followed by [Asset.readAsString]. |
+ /// |
+ /// If the asset was created from a [String] the original string is always |
+ /// returned and [encoding] is ignored. Otherwise, the binary data of the |
+ /// asset is decoded using [encoding], which defaults to [UTF8]. |
+ /// |
+ /// If an input with [id] cannot be found, throws an [AssetNotFoundException]. |
+ Future<String> readInputAsString(AssetId id, {Encoding encoding}) => |
+ _aggregate.readInputAsString(id, encoding: encoding); |
+ |
+ /// A convenience method to the contents of the input with [id]. |
+ /// |
+ /// This is equivalent to calling [getInput] followed by [Asset.read]. |
+ /// |
+ /// If the asset was created from a [String], this returns its UTF-8 encoding. |
+ /// |
+ /// If an input with [id] cannot be found, throws an [AssetNotFoundException]. |
+ Stream<List<int>> readInput(AssetId id) => _aggregate.readInput(id); |
+ |
+ /// A convenience method to return whether or not an asset exists. |
+ /// |
+ /// This is equivalent to calling [getInput] and catching an |
+ /// [AssetNotFoundException]. |
+ Future<bool> hasInput(AssetId id) => _aggregate.hasInput(id); |
+ |
+ /// Stores [output] as an output created by this transformation. |
+ /// |
+ /// A transformation can output as many assets as it wants. |
+ void addOutput(Asset output) => _aggregate.addOutput(output); |
+ |
+ /// Consume the primary input so that it doesn't get processed by future |
+ /// phases or emitted once processing has finished. |
+ /// |
+ /// Normally the primary input will automatically be forwarded unless the |
+ /// transformer overwrites it by emitting an input with the same id. This |
+ /// allows the transformer to tell barback not to forward the primary input |
+ /// even if it's not overwritten. |
+ void consumePrimary() => _aggregate.consumePrimary(primaryInput.id); |
+} |