anchor.diff:          negatable: false);
       parser.addOption(PORT_OPTION, help:
           "[port] the port on which the server will listen");
  +    parser.addOption(LOG_FILE_OPTION, help:
  +        "[path] file to log debugging messages to");
   
       ArgResults results = parser.parse(args);
       if (results[HELP_OPTION]) {
         _printUsage(parser);
         return;
  +    }
  +    if (results[LOG_FILE_OPTION] != null) {
  +      try {
  +        File file = new File(results[LOG_FILE_OPTION]);
  +        IOSink sink = file.openWrite();
  +        Logger.root.onRecord.listen((LogRecord record) {
  +          sink.writeln(record);
  +        });
  +      } catch (exception) {
  +        print('Could not open log file: $exception');
  +        exitCode = 1;
  +        return;
  +      }
       }
       int port;
       bool serve_http = false;
  
positive.code:    */
    static const String PORT_OPTION = "port";
  
    SocketServer socketServer = new SocketServer();
  
    HttpAnalysisServer httpServer;
  
negative.code: import 'package:analysis_server/src/socket_server.dart';
  import 'package:analysis_server/stdio_server.dart';
  import 'package:args/args.dart';
  import 'package:logging/logging.dart';
  
  /**
   * The [Driver] class represents a single running instance of the analysis
  