anchor.diff:                     hide: true);
       return parser;
   }
  -
  -
  
positive.code:                        'code based on Spine validation options.');
          stdout.writeln(parser.usage);
      } else {
          var descriptorPath = _getRequired(args, descriptorArgument);
          var destinationPath = _getRequired(args, destinationArgument);
          var stdPackage = args[stdPackageArgument];
          var importPrefix = args[importPrefixArgument];
  
          var shouldPrint = args.options.contains(stdoutFlag);
  
          var descFile = File(descriptorPath);
          _checkFile(descFile);
          var destinationFile = File(destinationPath);
          _ensureFile(destinationFile);
  
          FileDescriptorSet descriptors = _parseDescriptors(descFile);
          var properties = dart_code_gen.Properties(descriptors, stdPackage, importPrefix);
          var dartCode = dart_code_gen.generateValidators(properties);
          destinationFile.writeAsStringSync(dartCode, flush: true);
          if (shouldPrint) {
              stdout.write(dartCode);
          }
      }
  }
  
  
negative.code:     return registry;
  }
  
  ArgParser _createParser() {
      var parser = ArgParser();
      parser.addOption(descriptorArgument,
  