pkg/analyzer/lib/src/utilities/extensions/string.dart

// Copyright (c) 2020, 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.

extension ListOfStringExtension on List<String> {
  /// Produce a comma-separated representation of this list, with the last
  /// element preceded by 'and' when there are more than two elements in this
  /// list.
  String get commaSeparatedWithAnd => _commaSeparated('and');

  /// Produce a comma-separated representation of this list, with the last
  /// element preceded by 'or' when there are more than two elements in this
  /// list.
  String get commaSeparatedWithOr => _commaSeparated('or');

  /// Produce a comma-separated representation of this list, with the last
  /// element preceded by the [conjunction] when there are more than two
  /// elements in this list.
  String _commaSeparated(String conjunction) {
    if (length == 0) {
      return '';
    } else if (length == 1) {
      return this[0];
    } else if (length == 2) {
      return '${this[0]} $conjunction ${this[1]}';
    } else {
      var buffer = StringBuffer();
      for (int i = 0; i < length - 1; i++) {
        buffer.write(this[i]);
        buffer.write(', ');
      }
      buffer.write(conjunction);
      buffer.write(' ');
      buffer.write(this[length - 1]);
      return buffer.toString();
    }
  }
}