Roll Observatory packages and add a roll script

quiver/lib/src/async/future_stream.dart

-// Copyright 2014 Google Inc. All Rights Reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-part of quiver.async;
-
-/**
- * A Stream that will emit the same values as the stream returned by [future]
- * once [future] completes.
- *
- * If [future] completes to an error, the return value will emit that error and
- * then close.
- *
- * If [broadcast] is true, this will be a broadcast stream. This assumes that
- * the stream returned by [future] will be a broadcast stream as well.
- * [broadcast] defaults to false.
- *
- * # Example
- *
- * This class is useful when you need to retreive some object via a `Future`,
- * then return a `Stream` from that object:
- *
- *     var futureOfStream = getResource().then((resource) => resource.stream);
- *     return new FutureStream(futureOfStream);
- */
-class FutureStream<T> extends Stream<T> {
-  Future<Stream<T>> _future;
-  StreamController<T> _controller;
-  StreamSubscription _subscription;
-
-  FutureStream(Future<Stream<T>> future, {bool broadcast: false}) {
-    _future = future.catchError((e, stackTrace) {
-      // Since [controller] is synchronous, it's likely that emitting an error
-      // will cause it to be cancelled before we call close.
-      if (_controller != null) {
-        _controller.addError(e, stackTrace);
-        _controller.close();
-      }
-      _controller = null;
-    });
-
-    if (broadcast == true) {
-      _controller = new StreamController.broadcast(
-          sync: true, onListen: _onListen, onCancel: _onCancel);
-    } else {
-      _controller = new StreamController(
-          sync: true, onListen: _onListen, onCancel: _onCancel);
-    }
-  }
-
-  _onListen() {
-    _future.then((stream) {
-      if (_controller == null) return;
-      _subscription = stream.listen(_controller.add,
-          onError: _controller.addError, onDone: _controller.close);
-    });
-  }
-
-  _onCancel() {
-    if (_subscription != null) _subscription.cancel();
-    _subscription = null;
-    _controller = null;
-  }
-
-  StreamSubscription<T> listen(void onData(T event),
-      {Function onError, void onDone(), bool cancelOnError}) {
-    return _controller.stream.listen(onData,
-        onError: onError, onDone: onDone, cancelOnError: cancelOnError);
-  }
-
-  bool get isBroadcast => _controller.stream.isBroadcast;
-}