pkg/barback/lib/src/declaring_transform.dart

// 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.declaring_transform;

import 'asset_id.dart';
import 'base_transform.dart';
import 'transform_node.dart';

/// A transform for [DeclaringTransform]ers that allows them to declare the ids
/// of the outputs they'll generate without generating the concrete bodies of
/// those outputs.
class DeclaringTransform extends BaseTransform {
  final _outputIds = new Set<AssetId>();

  DeclaringTransform._(TransformNode node)
    : super(node);

  /// 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] declareds 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);
  }
}

/// The controller for [DeclaringTransform].
class DeclaringTransformController extends BaseTransformController {
  DeclaringTransform get transform => super.transform;

  /// The set of ids that the transformer declares it will emit for the given
  /// primary input.
  Set<AssetId> get outputIds => transform._outputIds;

  DeclaringTransformController(TransformNode node)
      : super(new DeclaringTransform._(node));
}