anchor.diff:        ]);
       }
       return new _ServeOptions._(
  +        hostName: argResults[_hostname] as String,
           serveTargets: serveTargets,
           assumeTty: argResults[_assumeTty] as bool,
           deleteFilesByDefault: argResults[_deleteFilesByDefault] as bool);
  
positive.code: 
  const _assumeTty = 'assume-tty';
  const _deleteFilesByDefault = 'delete-conflicting-outputs';
  
  /// Unified command runner for all build_runner commands.
  class BuildCommandRunner extends CommandRunner {
  
negative.code:         deleteFilesByDefault: options.deleteFilesByDefault,
          assumeTty: options.assumeTty);
      var servers = await Future.wait(options.serveTargets.map((target) =>
          serve(handler.handlerFor(target.dir), options.hostName, target.port)));
      await handler.currentBuild;
      for (var target in options.serveTargets) {
        stdout.writeln('Serving `${target.dir}` on port ${target.port}');
  