lib/src/barback/excluding_transformer.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.

import 'dart:async';

import 'package:barback/barback.dart';

import 'transformer_config.dart';

/// Decorates an inner [Transformer] and handles including and excluding
/// primary inputs.
class ExcludingTransformer extends Transformer {
  /// If [config] defines includes or excludes, wraps [inner] in an
  /// [ExcludingTransformer] that handles those.
  ///
  /// Otherwise, just returns [inner] unmodified.
  static Transformer wrap(Transformer inner, TransformerConfig config) {
    if (!config.hasExclusions) return inner;

    if (inner is LazyTransformer) {
      // TODO(nweiz): Remove these unnecessary "as"es when issue 19046 is fixed.
      return new _LazyExcludingTransformer(inner as LazyTransformer, config);
    } else if (inner is DeclaringTransformer) {
      return new _DeclaringExcludingTransformer(
          inner as DeclaringTransformer, config);
    } else {
      return new ExcludingTransformer._(inner, config);
    }
  }

  final Transformer _inner;

  /// The config containing rules for which assets to include or exclude.
  final TransformerConfig _config;

  ExcludingTransformer._(this._inner, this._config);

  isPrimary(AssetId id) {
    if (!_config.canTransform(id.path)) return false;
    return _inner.isPrimary(id);
  }

  Future apply(Transform transform) => _inner.apply(transform);

  String toString() => _inner.toString();
}

class _DeclaringExcludingTransformer extends ExcludingTransformer
    implements DeclaringTransformer {
  _DeclaringExcludingTransformer(
      DeclaringTransformer inner, TransformerConfig config)
      : super._(inner as Transformer, config);

  Future declareOutputs(DeclaringTransform transform) =>
      (_inner as DeclaringTransformer).declareOutputs(transform);
}

class _LazyExcludingTransformer extends _DeclaringExcludingTransformer
    implements LazyTransformer {
  _LazyExcludingTransformer(
      DeclaringTransformer inner, TransformerConfig config)
      : super(inner, config);
}