LanguageFeatures/Spread-collections/NullAware_A01_t04.dart

/*
 * Copyright (c) 2019, 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 To handle these gracefully, we support a [...?] "null-aware
 * spread" operator. In cases where the spread expression evaluates to [null],
 * that expands to an empty collection instead of throwing a runtime expression.
 *
 *  That turns the example to:
 *
 *   var command = [
 *   engineDartPath,
 *   '--target=flutter',
 *   ...?extraFrontEndOptions,
 *   mainPath
 *   ];
 * @description Checks that exception is thrown if spreadable element in the
 * [Set] is not null-aware and it's [null].
 * @author iarkh@unipro.ru
 */
// SharedOptions=--enable-experiment=constant-update-2018

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

Set getASet(
    String engineDartPath, List extraFrontEndOptions, String mainPath) {
  return(
      {engineDartPath, '--target=flutter', ...extraFrontEndOptions, mainPath});
}

main() {
  Set a;

  Expect.setEquals({"enginePath", "--target=flutter", "--option1", "mainPath"},
      getASet("enginePath", ["--option1"], "mainPath"));

  Expect.throws(() => a = getASet("enginePath", null, "mainPath"));
}