LibTest/async/StreamIterator/cancel_A01_t01.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 abstract void cancel()
 * Cancels the stream iterator (and the underlying stream subscription) early.
 
 * The stream iterator is automatically canceled if the moveNext future completes
 * with either false or an error.
 
 * If a moveNext call has been made, it will complete with false as value,
 * as will all further calls to moveNext.
 
 * If you need to stop listening for values before the stream iterator is automatically closed,
 * you must call cancel to ensure that the stream is properly closed.
 
 * @description Checks that call to cancel() makes subsequent call to moveNext() complete with false as value.
 * @author kaigorodov
 */

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

void check(List source, List expected) {
  List actual=new List();
  Stream stream=new Stream.fromIterable(source);
  StreamIterator streamIterator=new StreamIterator(stream);
  asyncStart();
  void step(bool hasNext) {
    if (!hasNext) {
      Expect.listEquals(expected, actual);
      asyncEnd();
      return;
    }
    if (streamIterator.current==null) {
      streamIterator.cancel();
    } else {
      actual.add(streamIterator.current);
    }
    streamIterator.moveNext().then(step);
  }
  streamIterator.moveNext().then(step);
}

main() {
  check([1,2,3,"end"], [1,2,3,"end"]);
  check([1,2,null,3,"end"], [1,2]);
}