LanguageFeatures/Spread-collections/NullAware_A01_t05.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.

// @dart = 2.9

/// @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 spreadable element of the [Map] can be null-aware
/// @author iarkh@unipro.ru


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

Map getAMap(
    String engineDartPath, Map extraFrontEndOptions, String mainPath) {
  return({1: engineDartPath, 2: "--target=flutter", ...?extraFrontEndOptions,
      3: mainPath});
}

main() {
  Expect.mapEquals(
      {1: "enginePath", 2: "--target=flutter", 0: "--option1", 3: "mainPath"},
      getAMap("enginePath", {0: "--option1"}, "mainPath"));
  Expect.mapEquals({1: "enginePath", 2: "--target=flutter", 3: "mainPath"},
      getAMap("enginePath", null, "mainPath"));
}