anchor.diff:          default = null;
           description = ''
             User account under which Klipper runs.
  +
             If null is specified (default), a temporary user will be created by systemd.
           '';
         };
  
positive.code:             mcu = lib.strings.sanitizeDerivationName mcu;
              inherit firmwareConfig;
            })
            cfg.firmware;
          firmwareFlasher = mapAttrsToList
            (mcu: firmware: pkgs.callPackage pkgs.klipper-flash.override {
              mcu = lib.strings.sanitizeDerivationName mcu;
              klipper-firmware = firmware;
              flashDevice = cfg.settings."${mcu}".serial;
              firmwareConfig = cfg.firmware."${mcu}".firmwareConfig;
            })
            firmwares;
        in
  
negative.code:         message = "Option klipper.group is not set when a user is specified.";
        }
        {
          assertion = foldl (a: b: a && b) true (mapAttrsToList (mcu: _: mcu != null -> (hasAttrByPath [ "${mcu}" "serial" ] cfg.settings)) cfg.firmwares);
          message = "Option klipper.settings.$mcu.serial must be set when klipper.firmware.$mcu is specified";
        }
      ];
  