anchor.diff:            "plugins=(${concatStringsSep " " cfg.plugins})"
           }
   
  -        ${optionalString (stringLength(cfg.custom) > 0)
  -          "ZSH_CUSTOM=\"${cfg.custom}\""
  +        ${optionalString (custom != null)
  +          "ZSH_CUSTOM=\"${custom}\""
           }
   
           ${optionalString (stringLength(cfg.theme) > 0)
  
positive.code: 
        environment.systemPackages = [ cfg.package ];
  
        programs.zsh.interactiveShellInit = with builtins; ''
          # oh-my-zsh configuration generated by NixOS
          export ZSH=${cfg.package}/share/oh-my-zsh
  
  
negative.code: 
          source $ZSH/oh-my-zsh.sh
        '';
  
        assertions = [
          {
            assertion = cfg.custom != null -> cfg.customPkgs == [];
            message = "If `cfg.custom` is set for `ZSH_CUSTOM`, `customPkgs` can't be used!";
          }
        ];
  
      };
    }
  