system.extraDependencies

[antifuchs]

This nixos option is really useful for warming the cache in a flake-based system configuration that has apps defined, and would be very good to have in nix-darwin as well: By adding the apps' derivations to the store, you get them pre-built (and referenced in the system closure so they don't get gc'ed) without having them clutter up the $PATH.

Here's a super minimal definition that I have in my system:

{ lib, config, ... }:
let
  cfg = config.nixos-compat;
in
{
  options = with lib; {
    nixos-compat.system.extraDependencies = mkOption {
      description = "Extra derivations to build & include in the
        system closure that are otherwise unreferenced.";
      type = types.listOf types.path;
      default = [ ];
    };
  };

  config = {
    environment.etc."nix/extra-dependencies.list" = {
      text = (toString cfg.system.extraDependencies);
    };
  };
}

This lets me add the following module to any darwin mods in my flake definition:

      prebuilt-flake-apps = system: { lib, ... }: {
        _file = "~/home#prebuilt-flake-apps";
        nixos-compat.system.extraDependencies =
          lib.mapAttrsToList (_n: app: app.program)
            (lib.filterAttrs (_n: app: app.type == "app") self.apps.${system});
      };