LibTest/async/Stream/firstWhere_A04_t01.test.dart

// Copyright (c) 2011, 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 Future<T> firstWhere (bool test(T element), T orElse()})
///
/// Finds the first element of this stream matching test.
///
/// Returns a future that is completed with the first element of this stream for
/// which test returns true.
///
/// If no such element is found before this stream is done, and an orElse
/// function is provided, the result of calling orElse becomes the value of the
/// future. If orElse throws, the returned future is completed with that error.
///
/// If this stream emits an error before the first matching element, the
/// returned future is completed with that error, and processing stops.
///
/// Stops listening to this stream after the first matching element or error has
/// been received.
///
/// Internally the method cancels its subscription after the first element that
/// matches the predicate. This means that single-subscription (non-broadcast)
/// streams are closed and cannot be reused after a call to this method.
///
/// If an error occurs, or if this stream ends without finding a match and with
/// no orElse function provided, the returned future is completed with an error.
///
/// @description Checks that non broadcast stream can not be listened after
/// the first element is returned.
/// @author a.semenov@unipro.ru

library firstWhere_A04_t01;

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

void check(Stream s) {
  asyncStart();
  s.firstWhere((_) => true).then((_) {
    if (!s.isBroadcast) {
      Expect.throws(() => s.listen((_) {}));
    }
    asyncEnd();
  });
}

void test(CreateStreamFunction create) {
  check(create([123]));
  check(create([1, 2, 3]));
}