anchor.diff:            output {
               ${cfg.outputConfig}
             }
  -        ''}";
  +        ''} ${optionalString cfg.enableWeb "-- web"}";
         };
       };
     };
  
positive.code: 
    config = mkIf cfg.enable {
      systemd.services.logstash = with pkgs; {
        description = "Logstash daemon";
        wantedBy = [ "multi-user.target" ];
  
        serviceConfig = {
  
negative.code:       enable = mkOption {
          default = false;
          description = "Enable logstash";
        };
  
        enableWeb = mkOption {
          default = false;
          description = "Enable logstash web interface";
        };
  
        inputConfig = mkOption {
  