Define and use NixOS module options within a flake.parts flake

heureka-code · August 25, 2026, 5:31pm

Hello,

I’m reading about flake.parts and co for a while now and today I tried to setup a basic flake with utility commands for the shell and by now I’m more confused than convinced (very confused).

I started with a template and added packages (what worked). Then I tried to add nixosModules with options and config, like I previously did in a normal flake. But, the new options aren’t accessible from the config part so my configuration can’t react to eventual settings from the user.

I tried multiple paths using perSystem. ..., config.programs. … and many more but none of them worked, the attributes are always “not found“. I assume such modules should go into flake. too but I also tried it with perSystem.`.

(When in line 49 with cfg.rgv.enable it errors as config.programs in the let binding isn’t available.)

As I was unable to find documentation/examples/other questions about this I’m doubting right now if I really understood what flake.parts is for if it doesn’t work with configurable nixosModules/`homeModules`. So do I have to do something special for module options? Is there some special way for finding out the attribute path without asking? I tried nix repl but it was of no use for this problem.

Thanks in advance!
hc

github.com/heureka-code/testutils.nix

modules/fuzzy-edit/default.nix

7e0566797

{
    lib,
    moduleWithSystem,
    ...
}: {
    perSystem = {
        self',
        pkgs,
        ...
    }: {
        # Allows definition of system-specific attributes
        # without needing to declare the system explicitly!
        #
        # Quick rundown of the provided arguments:
        # - config is a reference to the full configuration, lazily evaluated
        # - self' is the outputs as provided here, without system. (self'.packages.default)
        # - inputs' is the input without needing to specify system (inputs'.foo.packages.bar)
        # - pkgs is an instance of nixpkgs for your specific system
        # - system is the system this configuration is for

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EDIT:
This looks at least like someone wanted to achieve something similar but had no issue with this part: Using flake-parts, how to refer to `self.packages` from `flake.nixosModules`?

heureka-code · August 26, 2026, 8:12am

Finally I found a repository using this style and now it looks like it works (but it seems like documentation generation tools doesn’t understand it)

I’m unsure what was the important change but in the end I imported the following two files using imports and it worked.

github.com/heureka-code/testutils.nix

modules/fuzzy-edit/config.nix

20e3cd1d4

{
    self,
    lib,
    ...
}: {
    flake.nixosModules.fuzzy-edit = {
        pkgs,
        config,
        ...
    }: let
        cfg = config.programs;
    in {
        environment.systemPackages = lib.mkIf cfg.rg-fuzzy-edit.enable [
            (self.packages.${pkgs.stdenv.hostPlatform.system}.rg-fuzzy-edit.override {
                name = cfg.rg-fuzzy-edit.name;
                help = cfg.rg-fuzzy-edit.help;
                editor = cfg.rg-fuzzy-edit.editor;
            })
            (self.packages.${pkgs.stdenv.hostPlatform.system}.fd-fuzzy-edit.override {
                name = cfg.fd-fuzzy-edit.name;

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github.com/heureka-code/testutils.nix

modules/fuzzy-edit/options.nix

20e3cd1d4

{
    flake.nixosModules.fuzzy-edit = {
        lib,
        config,
        ...
    }: {
        options = {
            programs.rg-fuzzy-edit = {
                enable = lib.mkEnableOption "rgv";
                name = lib.mkOption {
                    type = lib.types.str;
                    default = "rgv";
                    description = "The name of the command to run";
                };
                help = lib.mkOption {
                    type = lib.types.str;
                    description = "The help text fzf should show during selection";
                    default = "Select matching line to open file in ${config.programs.rg-fuzzy-edit.editor}";
                };
                editor = lib.mkOption {

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