Stable and unstable nixpkgs

[aShabat]

Just read through the core principles. Is there a recommended way of mixing packages from stable and unstable?

[aShabat]

I'm thinking about this guide in flake.parts. Is it still the way with den or is there some better alternative?

[sini]

There are a number of ways to do this, including with den...

I, personally, just run unstable but I have support in my config to specify separate channels in my host-schema with instantiate overrides to switch between nixos-stable, nixos-unstable, and nixpkgs-master on the hosts themselves.

You can use pkg overlays to expose unstable packages to stable systems:

  unstable-packages = final: _prev: {
    unstable = import inputs.nixpkgs-unstable {
      inherit (final.stdenv.hostPlatform) system;
      config.allowUnfree = true;
    };
  };

Alternatively, you could use a policy.resolve to project a custom-pkgs object from the outer flake/den context into a class; but that's probably overkill for what you need. I do have a future vision with per-aspect pkg overrides as a first class pattern, but the reality is users probably don't need that -- overrides can solve this for 99% of user use cases.