anchor.diff:  
     config = mkIf cfg.enable {
   
  -    environment.etc."fish/foreign-env/shellInit".text = cfge.shellInit;
  -    environment.etc."fish/foreign-env/loginShellInit".text = cfge.loginShellInit;
  -    environment.etc."fish/foreign-env/interactiveShellInit".text = cfge.interactiveShellInit;
  -
  -    environment.etc."fish/nixos-env-preinit.fish".text = ''
  -      # This happens before $__fish_datadir/config.fish sets fish_function_path, so it is currently
  -      # unset. We set it and then completely erase it, leaving its configuration to $__fish_datadir/config.fish
  -      set fish_function_path ${pkgs.fish-foreign-env}/share/fish-foreign-env/functions $__fish_datadir/functions
  -      
  -      # source the NixOS environment config
  -      if [ -z "$__NIX_DARWIN_SET_ENVIRONMENT_DONE" ]
  -          fenv source ${config.system.build.setEnvironment}
  -      end
  -
  -      # clear fish_function_path so that it will be correctly set when we return to $__fish_datadir/config.fish
  -      set -e fish_function_path
  -    '';
  -
  -    environment.etc."fish/config.fish".text = ''
  -      # /etc/fish/config.fish: DO NOT EDIT -- this file has been generated automatically.
  -
  -      # if we haven't sourced the general config, do it
  -      if not set -q __fish_nix_darwin_general_config_sourced
  -        set fish_function_path ${pkgs.fish-foreign-env}/share/fish-foreign-env/functions $fish_function_path
  -        fenv source /etc/fish/foreign-env/shellInit > /dev/null
  -        set -e fish_function_path[1]
  -        
  -        ${cfg.shellInit}
  -
  -        # and leave a note so we don't source this config section again from
  -        # this very shell (children will source the general config anew)
  -        set -g __fish_nix_darwin_general_config_sourced 1
  -      end
  -
  -      # if we haven't sourced the login config, do it
  -      status --is-login; and not set -q __fish_nix_darwin_login_config_sourced
  -      and begin
  -        set fish_function_path ${pkgs.fish-foreign-env}/share/fish-foreign-env/functions $fish_function_path
  -        fenv source /etc/fish/foreign-env/loginShellInit > /dev/null
  -        set -e fish_function_path[1]
  -        
  -        ${cfg.loginShellInit}
  -
  -        # and leave a note so we don't source this config section again from
  -        # this very shell (children will source the general config anew)
  -        set -g __fish_nix_darwin_login_config_sourced 1
  -      end
  -
  -      # if we haven't sourced the interactive config, do it
  -      status --is-interactive; and not set -q __fish_nix_darwin_interactive_config_sourced
  -      and begin
  -        ${fishAliases}
  -        
  -
  -        set fish_function_path ${pkgs.fish-foreign-env}/share/fish-foreign-env/functions $fish_function_path
  -        fenv source /etc/fish/foreign-env/interactiveShellInit > /dev/null
  -        set -e fish_function_path[1]
  -        
  -        ${cfg.promptInit}
  -        ${cfg.interactiveShellInit}
  -
  -        # and leave a note so we don't source this config section again from
  -        # this very shell (children will source the general config anew,
  -        # allowing configuration changes in, e.g, aliases, to propagate)
  -        set -g __fish_nix_darwin_interactive_config_sourced 1
  -      end
  -    '';
  -
  -    # include programs that bring their own completions
  -    environment.pathsToLink = []
  -      ++ optional cfg.vendor.config.enable "/share/fish/vendor_conf.d"
  -      ++ optional cfg.vendor.completions.enable "/share/fish/vendor_completions.d"
  -      ++ optional cfg.vendor.functions.enable "/share/fish/vendor_functions.d";
  -    
  -    environment.systemPackages = [ pkgs.fish ];
  -
  +    environment = mkMerge [
  +      (mkIf cfg.useBabelfish
  +      {
  +        etc."fish/setEnvironment.fish".source = babelfishTranslate config.system.build.setEnvironment "setEnvironment";
  +        etc."fish/shellInit.fish".source = babelfishTranslate envShellInit "shellInit";
  +        etc."fish/loginShellInit.fish".source = babelfishTranslate envLoginShellInit "loginShellInit";
  +        etc."fish/interactiveShellInit.fish".source = babelfishTranslate envInteractiveShellInit "interactiveShellInit";
  +     })
  +
  +      (mkIf (!cfg.useBabelfish)
  +      {
  +        etc."fish/foreign-env/shellInit".source = envShellInit;
  +        etc."fish/foreign-env/loginShellInit".source = envLoginShellInit;
  +        etc."fish/foreign-env/interactiveShellInit".source = envInteractiveShellInit;
  +      })
  +
  +      {
  +        etc."fish/nixos-env-preinit.fish".text =
  +        if cfg.useBabelfish
  +        then ''
  +          # source the NixOS environment config
  +          if [ -z "$__NIX_DARWIN_SET_ENVIRONMENT_DONE" ]
  +            source /etc/fish/setEnvironment.fish
  +          end
  +        ''
  +        else ''
  +          # This happens before $__fish_datadir/config.fish sets fish_function_path, so it is currently
  +          # unset. We set it and then completely erase it, leaving its configuration to $__fish_datadir/config.fish
  +          set fish_function_path ${fenv}/share/fish-foreign-env/functions $__fish_datadir/functions
  +
  +          # source the NixOS environment config
  +          if [ -z "$__NIX_DARWIN_SET_ENVIRONMENT_DONE" ]
  +            fenv source ${config.system.build.setEnvironment}
  +          end
  +
  +          # clear fish_function_path so that it will be correctly set when we return to $__fish_datadir/config.fish
  +          set -e fish_function_path
  +        '';
  +      }
  +      {
  +        etc."fish/config.fish".text = ''
  +        # /etc/fish/config.fish: DO NOT EDIT -- this file has been generated automatically.
  +
  +        # if we haven't sourced the general config, do it
  +        if not set -q __fish_nix_darwin_general_config_sourced
  +          ${sourceEnv "shellInit"}
  +
  +          ${cfg.shellInit}
  +
  +          # and leave a note so we don't source this config section again from
  +          # this very shell (children will source the general config anew)
  +          set -g __fish_nix_darwin_general_config_sourced 1
  +        end
  +
  +        # if we haven't sourced the login config, do it
  +        status --is-login; and not set -q __fish_nix_darwin_login_config_sourced
  +        and begin
  +          ${sourceEnv "loginShellInit"}
  +
  +          ${cfg.loginShellInit}
  +
  +          # and leave a note so we don't source this config section again from
  +          # this very shell (children will source the general config anew)
  +          set -g __fish_nix_darwin_login_config_sourced 1
  +        end
  +
  +        # if we haven't sourced the interactive config, do it
  +        status --is-interactive; and not set -q __fish_nix_darwin_interactive_config_sourced
  +        and begin
  +          ${fishAliases}
  +
  +          ${sourceEnv "interactiveShellInit"}
  +
  +          ${cfg.promptInit}
  +          ${cfg.interactiveShellInit}
  +
  +          # and leave a note so we don't source this config section again from
  +          # this very shell (children will source the general config anew,
  +          # allowing configuration changes in, e.g, aliases, to propagate)
  +          set -g __fish_nix_darwin_interactive_config_sourced 1
  +        end
  +      '';
  +      }
  +
  +      # include programs that bring their own completions
  +      {
  +        pathsToLink = []
  +          ++ optional cfg.vendor.config.enable "/share/fish/vendor_conf.d"
  +          ++ optional cfg.vendor.completions.enable "/share/fish/vendor_completions.d"
  +          ++ optional cfg.vendor.functions.enable "/share/fish/vendor_functions.d";
  +      }
  +
  +      { systemPackages = [ pkgs.fish ]; }
  +    ];
     };
   
   }
  
positive.code:         '';
          type = types.bool;
        };
        
        vendor.config.enable = mkOption {
          type = types.bool;
          default = true;
  
negative.code:     mapAttrsFlatten (k: v: "alias ${k} '${v}'") cfg.shellAliases
    );
  
    envShellInit = pkgs.writeText "shellInit" cfge.shellInit;
  
    envLoginShellInit = pkgs.writeText "loginShellInit" cfge.loginShellInit;
  
    envInteractiveShellInit = pkgs.writeText "interactiveShellInit" cfge.interactiveShellInit;
  
    fenv = pkgs.fish-foreign-env or pkgs.fishPlugins.foreign-env;
  
    sourceEnv = file:
    if cfg.useBabelfish then
      "source /etc/fish/${file}.fish"
    else
      ''
        set fish_function_path ${fenv}/share/fish-foreign-env/functions $fish_function_path
        fenv source /etc/fish/foreign-env/${file} > /dev/null
        set -e fish_function_path[1]
      '';
  
    babelfishTranslate = path: name:
      pkgs.runCommand "${name}.fish" {
        nativeBuildInputs = [ cfg.babelfishPackage ];
      } "${cfg.babelfishPackage}/bin/babelfish < ${path} > $out;";
  
  in
  
  {
  