Add support for the other shells

              users.groups.${user.name} = {};

            '';

          }

          {

            assertion = (user.shell == pkgs.fish) -> (config.programs.fish.enable == true);

        ] ++ (map (shell: {

            assertion = (user.shell == pkgs.${shell}) -> (config.programs.${shell}.enable == true);

            message = ''

              users.users.${user.name}.shell is set to fish, but

              programs.fish.enable is not true. This will cause the fish shell

              to lack the basic nix directories in its PATH and might make

              users.users.${user.name}.shell is set to ${shell}, but

              programs.${shell}.enable is not true. This will cause the ${shell}

              shell to lack the basic nix directories in its PATH and might make

              logging in as that user impossible. You can fix it with:

              programs.fish.enable = true;

              programs.${shell}.enable = true;

            '';

          }

        ]

          }) [

          "fish"

          "xonsh"

          "zsh"

        ])

    ));

    warnings =