Template: Flake Parts Modules

Source

templates/flake-parts-modules

The flake-parts-modules template demonstrates how to use Den aspects that propagate custom classes into third-party flake-parts perSystem modules.

For demo purposes, the example showcases:

• perSystem.packages: How to expose flake-parts packages.
• numtide/devshell: A default devshell extensible by any aspect.
• numtide/treefmt-nix: A shared formatter configured across aspects.
• sini/files: Generates README from nix code.
• nix-community/nix-unit: Write tests directly on aspects.

Initialize

mkdir example && cd example
nix flake init -t github:denful/den#flake-parts-modules
nix flake update den
nix flake show
nix flake check -L

Project Structure

flake.nix
modules/
  den.nix                # Hosts, aspects using the classes, and pipeline wiring.
  perSystem-from-hosts.nix # Reads flake-parts classes from each host.
  pkgs-by-name.nix       # Wires drupol/pkgs-by-name-for-flake-parts.
  classes/
    packages.nix         # perSystem.packages.
    devshell.nix         # numtide/devshell.
    treefmt.nix          # numtide/treefmt-nix.
    files.nix            # sini/files.
    nix-unit.nix         # nix-community/nix-unit.
packages/
  hola.nix

Key points:

• A custom class file under modules/classes/ registers its class with den.classes.<name> = { };, imports the third-party flakeModule, then forwards content into the flake-parts scope with a route policy from den.lib.policy. (packages.nix reuses Den’s built-in packages class instead.)
• Classes are wired into the flake-parts scope via den.schema.flake-parts.includes, so any module can contribute new perSystem classes.

Next Steps

• Read flake.parts Documentation for more perSystem modules.