Add StreamSubscription.asFuture.

sdk/lib/async/stream.dart

 // Copyright (c) 2013, 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.
 
 part of dart.async;
 
 // -------------------------------------------------------------------
 // Core Stream types
 // -------------------------------------------------------------------
 
@@ skipping 814 matching lines @@
    *
    * If the subscription is paused more than once, an equal number
    * of resumes must be performed to resume the stream.
    */
   void pause([Future resumeSignal]);
 
   /**
    * Resume after a pause.
    */
   void resume();
+
+  /**
+   * Returns a future that handles the [onDone] and [onError] callbacks.
+   *
+   * This method *overwrites* the existing [onDone] and [onError] callbacks
+   * with new ones that complete the returned future.
+   *
+   * In case of an error the subscription will automatically cancel (even
+   * when it was listening with `unsubscribeOnError` set to `false`).

[Lasse Reichstein Nielsen, 2013/04/15 10:19:15]

"This also makes the subscription cancel on any error".

(Rename unsubscribeOnError to cancelOnError everywhere?)

What happens if you use asFuture, and then set a new onError handler,
overwriting the Future's handler? Will it still cancel on error or not?

[floitsch, 2013/04/15 12:16:37]

If you change the onError handler it won't receive the error and thus not
cancel.
I'm almost tempted to make the listener functions on Subscription private...

+   *
+   * In case of a `done` event the future completes with the given
+   * [futureValue].
+   */
+  Future asFuture([var futureValue]);
 }
 
 
 /**
  * An interface that abstracts creation or handling of [Stream] events.
  */
 abstract class EventSink<T> {
   /** Create a data event */
   void add(T event);
   /** Create an async error. */
@@ skipping 305 matching lines @@
 }
 
 class _EventOutputSinkWrapper<T> extends EventSink<T> {
   _EventOutputSink _sink;
   _EventOutputSinkWrapper(this._sink);
 
   void add(T data) { _sink._sendData(data); }
   void addError(AsyncError error) { _sink._sendError(error); }
   void close() { _sink._sendDone(); }
 }