How to fix `evaluation warning: 'system' has been renamed to/replaced by 'stdenv.hostPlatform.system'`

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21

okay, I switched it to:

              (
                {
                  pkgs,
                  inputs,
                  ...
                }:
                {
                  _module.args = {
                    unstablePkgs = import inputs.unstable {
                      inherit (pkgs) config overlays;
                      localSystem = pkgs.stdenv.hostPlatform;

                    };
                  };
                }
              )

and it does work indeed. Thank you very much !

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22

@Erwyn also see specialArgs

23

_module.args is preferable over specialArgs, where possible. (In this case, itā€™s possible.)

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24

I was so confused after I got this warning when I was still using Determinate Nix. Currently Iā€™m redoing my whole config to use upstream Nix and still got the same error after running the check.

At first I thought it was only related to determinate. I guess I didnā€™t keep up with the nixpkgs changes until recently lmao

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25

Thanks for the helpful information! In my case it was caused by this:

https://gitlab.com/ahoneybun/nix-configs/-/blob/main/flake.nix?ref_type=heads#L89

Changing:

${prev.system}

to this:

${prev.stdenv.hostPlatform.system}

fixed it for me.

26

Use final not prev, whenever possible.

1 Like
27

What is the difference in this context? It does seem to replace the version of helix from nixpkgs with the upstream tagged version.

28

final doesnā€™t depend on overlay ordering. This makes more sense for stdenv, and especially stdenv.hostPlatform.system, because you want to get the ā€œfinalā€ value of those, after all other overlays have been applied. In practice it should rarely make a difference, but itā€™s one of those little details.

See also the wiki entry for this, itā€™s actually one of the better pages: Overlays - Official NixOS Wiki

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29

Hereā€™s an example where it really mattered: Packages in overlay arguments are different from regular package-set?

Stuff like system and stdenv are involved in bootstrap, so prev.system and prev.stdenv are not things you should rely on.

And in general itā€™s always a best-practice to use final in an overlay, except for obvious infrec scenarios, e.g. for foobar = prev.foobar.override { ... } where youā€™d have to use prev as final would infrec. You want your overlays to actually take effect - final is the nixpkgs instance that ensures that.

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