More tests for async* functions

tests/language/async_star_cancels_after_await_test.dart

+// Copyright (c) 2016, 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.
+
+import "dart:async";
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+
+var events = [];
+
+ticker(period) async* {
+  var timer;
+  var sc;
+  sc = new StreamController(onListen: () {
+    events.add("listen");
+    timer = new Timer.periodic(period, (_) {
+      sc.add(null);
+    });
+  }, onCancel: () {
+    events.add("cancel");
+    timer.cancel();
+  });
+
+  try {
+    var counter = 0;
+    await for (var tick in sc.stream) {
+      counter++;

[Lasse Reichstein Nielsen, 2016/02/08 21:04:35]

should there be a yield here?

[floitsch, 2016/02/09 16:56:34]

No.
I thought that async* functions can be canceled at await-points, too.

Modified this test to check that we only cancel at yield points (or never, if
there isn't any).

+    }
+  } finally {
+    events.add("finally");
+  }
+}
+
+void main() {
+  asyncStart();
+  events.add("main");
+  final subscription =
+      ticker(const Duration(milliseconds: 20)).listen((val) { });
+
+  new Timer(const Duration(milliseconds: 100), () async {
+    await subscription.cancel();
+    Expect.listEquals(["main", "listen", "cancel", "finally"], events);
+    asyncEnd();
+  });
+}