Language/Statements/Yield_and_Yield_Each/Yield_Each/execution_sync_t04.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 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 immediately enclosing function m is marked sync*, then:
 * 1. It is a dynamic error if the class of o does not implement Iterable.
 * Otherwise
 * 2. The method iterator is invoked upon o returning an object i.
 * 3. The moveNext method of i is invoked on it with no arguments. If moveNext
 * returns false execution of s is complete. Otherwise
 * 4. The getter current is invoked on i. If the invocation raises an
 * exception ex, execution of s throws ex. Otherwise, the result x of the
 * getter invocation is added to the iterable associated with m. Execution of
 * the function m immediately enclosing s is suspended until the nullary method
 * moveNext() is invoked upon the iterator used to initiate the current
 * invocation of m, at which point execution of s continues at 3.
 * 5. The current call to moveNext() returns true.
 *
 * @description Check that if the method moveNext returns false, then
 * execution of s is complete
 *
 * @author a.semenov@unipro.ru
 */
import '../../../../Utils/expect.dart';

bool moveNextResult = true;

class IteratorStub extends Iterator<int> {

  late int _moveNextCallCount;

  IteratorStub() {
    _moveNextCallCount = 0;
  }

  @override
  int get current => _moveNextCallCount;

  @override
  bool moveNext() {
    _moveNextCallCount++;
    return moveNextResult;
  }
}

class IterableStub extends Iterable<int> {

  Iterator<int> get iterator => new IteratorStub();
}

Iterable generator(Iterable iterable, List log) sync* {
  log.add('before');
  yield* iterable;
  log.add('after');
}

test1() {
  List log = [];
  moveNextResult = false;
  IterableStub its = new IterableStub();
  Expect.isTrue(generator(its, log).isEmpty);
  Expect.listEquals(['before', 'after'], log);
}

test2() {
  List log = [];
  moveNextResult = true;
  IterableStub its = new IterableStub();
  Iterable g = generator(its, log);
  Iterator i = g.iterator;
  Expect.isTrue(i.moveNext());
  Expect.equals(1, i.current);
  Expect.listEquals(['before'], log);
  Expect.isTrue(i.moveNext());
  Expect.equals(2, i.current);
  Expect.listEquals(['before'], log);
  moveNextResult = false;
  Expect.isFalse(i.moveNext());
  Expect.listEquals(['before', 'after'], log);
}

main() {
  test1();
  test2();
}