NixOS/nixpkgs?dir=lib

[dezren39]

idk where flakehub exists but i was wondering about something so im just gonna try here.

at some point subflakes i use had dependencies on nixpkg-lib and so to sync all the nixpkg reducing lock file,

i added a git flake to the same nixpkg i use but with lib subdir.

maybe that's not the right way to do it. i'm still adapting to nix.

if i wanted to use flakehub, i don't think that would work.

i looked in the documentation and the dir option seems to be git specific.

• https://github.com/NixOS/nix/blob/master/src/nix/flake.md#examples
• https://github.com/NixOS/nix/blob/master/src/nix/flake.md#types

i notice that the documentation only mentions the dir flag for git but i'm using it for github.

maybe it already works for tarballs? i should have just tried it?

or maybe what i'm doing with github provider is already wrong,
but i copied someone else's code so i'm unsure.

does it make send to make a nixpkgs-lib tar and distribute that as well?

    nixpkgs.url = "github:NixOS/nixpkgs";
    nixpkgs-lib = {
      url = "github:NixOS/nixpkgs?dir=lib";
    };
# and then setup follows for each of these where used in sub-flakes.

maybe i need to restructure something like this? https://zimbatm.com/notes/1000-instances-of-nixpkgs
or there is some magic like using git+file here? NixOS/nix#3978 (comment)

[Lord-Valen]

  nixpkgs.url = "github:NixOS/nixpkgs";
  nixpkgs-lib = {
    url = "github:NixOS/nixpkgs?dir=lib";
  };

I don't see why anyone should do this when they can simply access inputs.nixpkgs.lib.

[dezren39]

how do i set a dependent flake to use that? can i say follows "nixpkgs.lib"?

[Lord-Valen]

You shouldn't really need a follows. lib is an output of nixpkgs, so you can just access it directly.

{
	inputs.nixpkgs.url = "https://flakehub.com/f/NixOS/nixpkgs/0.1.0.tar.gz"; # nixpkgs-unstable
	outputs = { nixpkgs, ... }: let
		inherit (nixpkgs) lib;
		list1 = ["a" "b"];
		list2 = ["c"];
    in {
		foo = lib.concatLists [list1 list2]; # ["a" "b" "c"]
	};
}

[dezren39]

I guess what I mean is, I understand that. I don't intend to do that in my own flake, but I have a flake I want to use. How do I ensure that this flake, when referenced in my flake, gets the same nixpkgs lib as the one I use?

https://github.com/hercules-ci/flake-parts/blob/main/flake.nix

{
  description = "Flake basics described using the module system";

  inputs = {
    nixpkgs-lib.url = "github:NixOS/nixpkgs/nixos-unstable?dir=lib";
  };
<...>
}

and in my flake

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs";
    nixpkgs-lib.url = "github:NixOS/nixpkgs?dir=lib";
<...>
    flake-parts = {
      url = "github:hercules-ci/flake-parts";
      inputs.nixpkgs-lib.follows = "nixpkgs-lib";
    };
<...>
}

I'm happy to offer a PR upstream if that's best? I don't know the exact reasoning to target the lib flake in flake-parts.

[Lord-Valen]

Ah. If you look, flake-parts only accesses nixpkgs-lib.lib (which is, in fact, the only output) which will be the same as nixpkgs.lib. So I would just have nixpkgs-lib follow nixpkgs or nixpkgs-lib, if you're already using it. The motivation is probably to reduce size and avoid 1000 nixpkgs.

[dezren39]

thank you! i did not understand that I could pass nixpkgs to nixpkgs-lib. I guess I understand how this works, it surprised me though. I will try to look closer at how the deps get used next time and try to decipher. Switching to flakehub soon. :-)