Can flake-parts help with sharing code with nixosModules/darwinModules exports?

[z0al]

Given the following flake:

{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";

    flake-parts.url = "github:hercules-ci/flake-parts";
  };

  outputs =
    { self
    , nixpkgs
    , flake-parts
    , ...
    }@inputs:
    let 
      # Q: How to ensure this is passed to nixosModules/darwinModules?
      lib = nixpkgs.lib.extend
        (final: prev: (import ./lib final));
    in 
    flake-parts.lib.mkFlake { inherit inputs; } {
      systems = [
        ...
      ];

      flake = {
        nixosModules.default = import ./module.nix;
        darwinModules.default = import ./darwin-module.nix;
      };
    };
}

How do I pass my custom lib to nixosModules.default?

I tried import ./module.nix { inherit lib;} but then it asks for config and other parameters I don't know how to provide.

Alternatively: what's the easiest way to share code (read custom helpers) between these exports in my case?

[roberth]

I think you're looking for importApply

You can use it to pass anything to a module file.
Basically your module file will be a function to a module, arity 2:

{ self, customThing }:
{ config, withSystem, ... }:
{
  # module attrs
}

I would recommend to use a name that's not lib for anything other than the Nixpkgs lib, but some will disagree with that :)

import ./module.nix

import will throw away the file name, and the module system won't know where it came from, leading to worse error messages.
importApply solves that problem.
If you did't need to pass anything custom, it's better to do nixosModules.default = ./module.nix; etc. Also applies to imports, options of type deferredModule, and anywhere a module can be passed.

[z0al]

Basically your module file will be a function to a module

Oops, I thought I had a look at importApply before but somehow missed the point about that part so ofc it didn't work 🤦🏻‍♂️

Thanks a lot.

[z0al]

I should be able to use importApply even in the nested context, right? meaning if top-level nixosModule imports other sub-modules via imports = [...] that also need access to myLib

[roberth]

Yes, it returns a module, that can be used in those places.