Run pub tests against older versions of barback.

third_party/pkg/barback-0.13.0/lib/src/declaring_transform.dart

Index: third_party/pkg/barback-0.13.0/lib/src/declaring_transform.dart
diff --git a/third_party/pkg/barback-0.13.0/lib/src/declaring_transform.dart b/third_party/pkg/barback-0.13.0/lib/src/declaring_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.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>();
+
+  final AssetId primaryId;
+
+  DeclaringTransform._(TransformNode node)
+      : primaryId = node.primary.id,
+        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));
+}