| // 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. |
| |
| // @dart = 2.9 |
| |
| /// @assertion Execution of a statement s of the form yield e; proceeds as |
| /// follows: |
| /// First, the expression e is evaluated to an object o. If the enclosing |
| /// function m is marked async* and the stream u associated with m has been |
| /// paused, then execution of m is suspended until u is resumed or canceled. |
| /// Next, o is added to the iterable or stream associated with the immediately |
| /// enclosing function. |
| /// If the enclosing function m is marked async* and the stream u associated |
| /// with m has been canceled, then let c be the finally clause (17.11) of the |
| /// innermost enclosing try-finally statement, if any. If c is defined, let h be |
| /// the handler induced by c. If h is defined, control is transferred to h. If |
| /// h is undefined, the immediately enclosing function terminates. |
| /// The stream associated with an asynchronous generator could be canceled by |
| /// any code with a reference to that stream at any point where the generator |
| /// was passivated. Such a cancellation constitutes an irretrievable error for |
| /// the generator. At this point, the only plausible action for the generator |
| /// is to clean up after itself via its finally clauses. |
| /// Otherwise, if the enclosing function m is marked async* (9) then the |
| /// enclosing function may suspend. |
| /// |
| /// @description Check that If the enclosing function m is marked async* and |
| /// the stream u associated with m has been paused, then execution of m is |
| /// suspended until u is canceled. |
| /// @Issue 42584 |
| /// |
| /// @author a.semenov@unipro.ru |
| |
| import 'dart:async'; |
| import '../../../../Utils/expect.dart'; |
| |
| bool paused = false; |
| bool generatorActive = true; |
| |
| Stream<int> generator(List log) async* { |
| int i = 0; |
| while (generatorActive) { |
| if (paused) { |
| yield i; |
| log.add(i); |
| i++; |
| } |
| } |
| } |
| |
| test() async { |
| List log = []; |
| Stream<int> s = generator(log); |
| StreamSubscription<int> ss = s.listen( |
| (int i) { |
| } |
| ); |
| |
| ss.pause(); |
| paused = true; // force generator to yield |
| log.add('a'); |
| await new Future.delayed(new Duration(milliseconds: 100)); |
| log.add('b'); |
| generatorActive = false; |
| paused = false; |
| await ss.cancel(); |
| Expect.listEquals(['a', 'b', 0], log); |
| asyncEnd(); |
| } |
| |
| main() { |
| asyncStart(); |
| test(); |
| } |