anchor.diff:            enableAuthCodes: !disableServiceAuthCodes,
             ipv6: ipv6,
           );
  -      unawaited(_ddsInstance?.done.whenComplete(() {
  +      unawaited(_ddsInstance.done.whenComplete(() {
           if (!_completer.isCompleted) {
             _completer.complete();
           }
         }));
  -      logger.printTrace('DDS is listening at ${_ddsInstance?.uri}.');
  +      logger.printTrace('DDS is listening at ${_ddsInstance.uri}.');
       } on dds.DartDevelopmentServiceException catch (e) {
         logger.printTrace('Warning: Failed to start DDS: ${e.message}');
         if (e.errorCode == dds.DartDevelopmentServiceException.existingDdsInstanceError) {
  
positive.code: // Copyright 2014 The Flutter Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  import 'dart:async';
  
  
negative.code: /// Helper class to launch a [dds.DartDevelopmentService]. Allows for us to
  /// mock out this functionality for testing purposes.
  class DartDevelopmentService {
    dds.DartDevelopmentService _ddsInstance;
  
    Uri get uri => _ddsInstance?.uri ?? _existingDdsUri;
    Uri _existingDdsUri;
  
    Future<void> get done => _completer.future;
    final Completer<void> _completer = Completer<void>();
  