anchor.diff:        return null;
       }
   
  -    final json = jsonDecode(response.body);
  +    return response.body;
  +  }
   
  -    assert(json['name'] == packageName);
  -
  -    final versions = (json['versions'] as List)
  -        .map((str) => Version.parse(str as String))
  -        .toList();
  -
  -    final primary = primaryVersion(versions, includePreRelease);
  -
  -    return primary;
  +  void _print(Object value) {
  +    if (_debug) {
  +      stderr.writeln('  $value');
  +    }
     }
   }
   
  
positive.code: import 'util.dart';
  
  class PubDataService extends Service {
    final _client = http.Client();
  
    void close() => _client.close();
  
negative.code:     assert(Directory(directory).existsSync());
  
      final pubspecPath = p.join(directory, 'pubspec.yaml');
  
      _print('open pubspec: $pubspecPath');
  
      return Pubspec.parse(
        File(pubspecPath).readAsStringSync(),
  