| // 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.base_transform; |
| |
| import 'dart:async'; |
| |
| import '../asset/asset_id.dart'; |
| import '../graph/transform_node.dart'; |
| import '../log.dart'; |
| import 'transform_logger.dart'; |
| |
| /// The base class for the ephemeral transform objects that are passed to |
| /// transformers. |
| /// |
| /// This class provides the transformers with inputs, but its up to the |
| /// subclasses to provide a means of emitting outputs. |
| abstract class BaseTransform { |
| final TransformNode _node; |
| |
| /// The ids of primary inputs that should be consumed. |
| /// |
| /// This is exposed by [BaseTransformController]. |
| final _consumedPrimaries = new Set<AssetId>(); |
| |
| /// Whether the transformer logged an error. |
| /// |
| /// This is exposed via [BaseTransformController]. |
| bool _loggedError = false; |
| |
| /// The controller for the stream of log entries emitted by the transformer. |
| /// |
| /// This is exposed via [BaseTransformController]. |
| /// |
| /// This is synchronous because error logs can cause the transform to fail, so |
| /// we need to ensure that their processing isn't delayed until after the |
| /// transform or build has finished. |
| final _onLogController = new StreamController<LogEntry>.broadcast(sync: true); |
| |
| /// A logger so that the [Transformer] can report build details. |
| TransformLogger get logger => _logger; |
| TransformLogger _logger; |
| |
| BaseTransform(this._node) { |
| _logger = new TransformLogger((asset, level, message, span) { |
| if (level == LogLevel.ERROR) _loggedError = true; |
| |
| // If the log isn't already associated with an asset, use the primary. |
| if (asset == null) asset = _node.info.primaryId; |
| var entry = new LogEntry(_node.info, asset, level, message, span); |
| |
| // The log controller can be closed while log entries are still coming in |
| // if the transformer is removed during [apply]. |
| if (!_onLogController.isClosed) _onLogController.add(entry); |
| }); |
| } |
| |
| /// Consume a primary input so that it doesn't get processed by future |
| /// phases or emitted once processing has finished. |
| /// |
| /// Normally each 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 a primary input |
| /// even if it's not overwritten. |
| void consumePrimary(AssetId id) { |
| // TODO(nweiz): throw an error if an id is consumed that wasn't listed as a |
| // primary input. |
| _consumedPrimaries.add(id); |
| } |
| } |
| |
| /// The base class for controllers of subclasses of [BaseTransform]. |
| /// |
| /// Controllers are used so that [TransformNode]s can get values from a |
| /// [BaseTransform] without exposing getters in the public API. |
| abstract class BaseTransformController { |
| /// The [BaseTransform] controlled by this controller. |
| BaseTransform get transform; |
| |
| /// The ids of primary inputs that should be consumed. |
| Set<AssetId> get consumedPrimaries => transform._consumedPrimaries; |
| |
| /// Whether the transform logged an error. |
| bool get loggedError => transform._loggedError; |
| |
| /// The stream of log entries emitted by the transformer during a run. |
| Stream<LogEntry> get onLog => transform._onLogController.stream; |
| |
| /// Whether the transform's input or id stream has been closed. |
| /// |
| /// See also [done]. |
| bool get isDone; |
| |
| /// Mark this transform as finished emitting new inputs or input ids. |
| /// |
| /// This is distinct from [cancel] in that it *doesn't* indicate that the |
| /// transform is finished being used entirely. The transformer may still log |
| /// messages and load secondary inputs. This just indicates that all the |
| /// primary inputs are accounted for. |
| void done(); |
| |
| /// Mark this transform as canceled. |
| /// |
| /// This will close any streams and release any resources that were allocated |
| /// for the duration of the transformation. Unlike [done], this indicates that |
| /// the transformation is no longer relevant; either it has returned, or |
| /// something external has preemptively invalidated its results. |
| void cancel() { |
| done(); |
| transform._onLogController.close(); |
| } |
| } |