Language/Statements/Yield_and_Yield_Each/Yield_Each/execution_async_t10.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.

/// @assertion If m is marked async*, then:
///    • It is a dynamic error if the class of o does not implement Stream.
///  Otherwise
///    • For each element xcancelled of o:
///    – If the stream u associated with m has been paused, then execution
/// of m is suspended until u is resumed or canceled.
///    – If the stream u associated with m has been canceled, then let c be
/// the finally clause 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.
///    – Otherwise, x is added to the stream associated with m in the order
/// it appears in o. The function m may suspend.
///    • If the stream o is done, execution of s is complete.
///
/// @description Check that if the stream u associated with m has been
/// canceled and there are several enclosing try finally statement, then each
/// finally clause is executed in innermost-first order.
///
/// @issue 25748, 34775
/// @author a.semenov@unipro.ru

import 'dart:async';
import '../../../../Utils/expect.dart';

Stream<String> generator(Stream<String> input, List log) async* {
  bool cancelled = true;
  int order = 0;
  try {
    try {
      try {
        yield* input;
        cancelled = false;
      } finally {
        if (cancelled) {
          log.add(order++);
        }
      }
    } finally {
      if (cancelled) {
        log.add(order++);
      }
    }
  } finally {
    if (cancelled) {
      log.add(order++);
    }
  }
}

Future test() async {
  List log = [];
  StreamController<String> sc = new StreamController<String>();
  Stream<String> s = generator(sc.stream, log);
  StreamSubscription<String> ss = s.listen(
      (String v) {
        log.add(v);
      }
  );
  sc.add('a');
  sc.add('b');
  sc.add('c');
  await new Future.delayed(new Duration(milliseconds: 100));
  ss.cancel();
  sc.add('d');
  sc.add('e');
  await new Future.delayed(new Duration(milliseconds: 100));
  Expect.listEquals(['a', 'b', 'c', 0, 1, 2], log);
  await sc.close();
}

main() {
  asyncStart();
  test().then((_) => asyncEnd());
}