Add a filesystem descriptor library to scheduled_test.

pkg/scheduled_test/lib/src/utils.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.
 
 library utils;
 
 import 'dart:async';
 
 /// Configures [future] so that its result (success or exception) is passed on
 /// to [completer].
 void chainToCompleter(Future future, Completer completer) {
   future.then((value) => completer.complete(value),
       onError: (e) => completer.completeError(e.error, e.stackTrace));
 }
 
 /// Prepends each line in [text] with [prefix].
 String prefixLines(String text, {String prefix: '| '}) =>
   text.split('\n').map((line) => '$prefix$line').join('\n');
 
 /// Returns a [Future] that completes after pumping the event queue [times]
 /// times. By default, this should pump the event queue enough times to allow
 /// any code to run, as long as it's not waiting on some external event.
 Future pumpEventQueue([int times=200]) {
   if (times == 0) return new Future.immediate(null);
   return new Future.immediate(null).then((_) => pumpEventQueue(times - 1));
 }
+
+/// Returns whether [iterable1] has the same elements in the same order as
+/// [iterable2]. The elements are compared using `==`.
+bool orderedIterableEquals(Iterable iterable1, Iterable iterable2) {
+  var iter1 = iterable1.iterator;
+  var iter2 = iterable2.iterator;
+
+  while (true) {
+    if (iter1.current != iter2.current) return false;

[Bob Nystrom, 2013/02/22 17:58:21]

The iterator protocol says you need to call moveNext() once to advance to the
first item. This will coincidentally work because it also says conforming types
should return null from current if moveNext() has not been called yet, but it
feels a bit shady to rely on that since you aren't actually comparing items
here.

You should be able to just move this to the end of the loop.

[nweiz, 2013/02/22 20:57:20]

Done.

+    var hasNext1 = iter1.moveNext();
+    var hasNext2 = iter2.moveNext();
+    if (hasNext1 != hasNext2) return false;
+    if (!hasNext1) return true;
+  }
+}
+
+/// Returns a [Stream] that will immediately emit [error] and then close.

[Bob Nystrom, 2013/02/22 17:58:21]

Given corelib has Future.immediateError, I wonder if it should have new
Stream.immediateError too? File a bug?

[nweiz, 2013/02/22 20:57:20]

Done.

+Stream errorStream(error) => new Future.immediateError(error).asStream();
+
+/// Returns a buffered 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.
+Stream liftStream(Future<Stream> future) {

[Bob Nystrom, 2013/02/22 17:58:21]

Instead of "lift", how about "deferred" or just "future"? It wasn't clear to me
what this did at the callsite.

[nweiz, 2013/02/22 20:57:20]

Done.

+  var controller = new StreamController();
+  future.then((stream) {
+    stream.listen(
+        controller.add,
+        onError: (error) => controller.signalError(error),
+        onDone: controller.close);
+  }).catchError((e) {
+    controller.signalError(e);
+    controller.close();
+  });
+  return controller.stream;
+}