Add new features to package:async.

lib/src/delegates.dart

+// Copyright (c) 2015, 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 async.streams.delegates;

[nweiz, 2015/06/12 01:24:22]

Library annotations should match the path to the library (here and elsewhere).

Also, I'd call this file "delegating_stream_subscription". It would be nice to
keep this one-class-per-file, but even if not, the name should reflect the
current contents rather than the future contents.

[Lasse Reichstein Nielsen, 2015/06/12 13:04:19]

Without the "src" I assume. 
I originally expected to have a streams library exposing this, but dropped it
without changing the library name, so this is a bug.

Not that library names matter the slightest bit ;).
That's fine. If there is no particular reason to keep two classees in the same
library, they might as well each get their own.

[nweiz, 2015/06/16 01:05:22]

They matter exactly inasmuch as tools will complain if they conflict, which is
just enough to make it necessary to ensure their uniqueness :-/.

+
+import 'dart:async';
+
+/// Simple delegating wrapper around a [StreamSubscription].
+///
+/// Subclasses can override individual methods.
+class DelegatingStreamSubscription<T> implements StreamSubscription<T> {
+  final StreamSubscription _source;
+
+  DelegatingStreamSubscription(StreamSubscription subscription)
+      : _source = subscription;
+
+  void onData(void handleData(T data)) {
+    _source.onData(handleData);
+  }
+
+  void onError(Function handleError) {
+    _source.onError(handleError);
+  }
+
+  void onDone(void handleDone()) {
+    _source.onDone(handleDone);
+  }
+
+  void pause([Future resumeFuture]) {
+    _source.pause(resumeFuture);
+  }
+
+  void resume() {
+    _source.resume();
+  }
+
+  Future cancel() {
+    return _source.cancel();
+  }
+
+  Future asFuture([futureValue]) {
+    return _source.asFuture(futureValue);
+  }
+
+  bool get isPaused => _source.isPaused;
+}