Fix assertion that config.nixpkgs cannot be set if useGlobalPkgs is enabled

[justDeeevin]

Description

When useGlobalPkgs is enabled, setting nixpkgs.config and nixpkgs.overlays in the home config has no effect. There is an assertion in place intended to throw an error if the user tries to set these options in this scenario, but it uses an OR instead of an AND, allowing for one of them to be set. This PR replaces this OR for an AND.

Fixes #6079.

Checklist

• Change is backwards compatible.

• Code formatted with ./format.

• Code tested through nix-shell --pure tests -A run.all or nix develop --ignore-environment .#all using Flakes.

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Maintainer CC

@thiagokokada

[justDeeevin]

Been a minute... what's left to get this merged?

[Adda0]

LGTM. I do not think there is anything left to do. The PR just needs to wait for someone to merge it.

[thiagokokada]

CC @rycee .

[Zerodya]

I updated my flake.lock this morning only to get this failed assertions error:

error:
       … while calling the 'head' builtin
         at /nix/store/brjzz8wv5k09bq0yrvhc1j4hd8677k21-source/lib/attrsets.nix:1574:11:
         1573|         || pred here (elemAt values 1) (head values) then
         1574|           head values
             |           ^
         1575|         else

       … while evaluating the attribute 'value'
         at /nix/store/brjzz8wv5k09bq0yrvhc1j4hd8677k21-source/lib/modules.nix:853:9:
          852|     in warnDeprecation opt //
          853|       { value = addErrorContext "while evaluating the option `${showOption loc}':" value;
             |         ^
          854|         inherit (res.defsFinal') highestPrio;

       (stack trace truncated; use '--show-trace' to show the full trace)

       error:
       Failed assertions:
       - alpha profile: `nixpkgs` options are disabled when `home-manager.useGlobalPkgs` is enabled.

Now, I haven't found any nixpkgs options in my home config, and we all know how unhelpful nix errors are. So maybe this should've been a warning and not an error, since I can't update my system anymore even though it was not broken before.

Anyway, I set useGlobalPkgs = false; in my flake, but now home-manager can't see the allowUnfreePredicate I have set in my system and complains that it can't install some of my packages. I couldn't find any documentation about how to allow unfree packages in home-manager so maybe someone here could help me with this?

[panchoh]

@Zerodya, if you use stylix, check this issue.

[Zerodya]

Ah, I do. Thank you for pointing me there, I will follow that issue now.

[gaelj]

Same problem here (home manager + stylix + hyprpanel). Hyprpanel is impacted as well.

+1 for it to be a warning rather than a hard error, so that we can continue to update home manager until all concerned upstreams have fixed the bug on their side.

[tuxiqae]

In my case it broke my allowUnfree settings:

nixpkgs.config.allowUnfree = true;
nixpkgs.config.allowUnfreePredicate = _: true;

- <myUser> profile: `nixpkgs` options are disabled when `home-manager.useGlobalPkgs` is enabled.

Not sure why, since it's not like it was broken before I guess.

[brckd]

The error has been temporarily removed as of #6466, so updating Home Manager should fix it, but make sure to adapt your configurations nonetheless.

[Silveere]

If anybody wants a solution that lets you have the advantages of useGlobalPkgs while still letting you configure Home Manager's instance of nixpkgs, my solution was to write a custom submodule for the home-manager.users option in NixOS which injects the config and overlays from the system nixpkgs instance into each user's home-manager instance. Here is how I implemented it:

https://github.com/Silveere/nixfiles/blob/cab0e3e023c85dd85d6944ca068c4e4d373a781c/flake/system.nix#L172-L219

This is part of a flake-parts module that creates my nixosConfiguration outputs, and it does some other unrelated things as well. The important parts are 199-207 and 216-218. Keep in mind that the config arg used in line 204 comes from NixOS, not Home Manager.

Perhaps a similar implementation could be added to Home Manager, but there might be some unforeseen problems with this approach (e.g., if a user overrides _module.args.pkgs in NixOS, although I'd imagine this would cause much bigger problems and is probably an extreme edge case).

[gaelj]

Here is @Silveere 's solution adapted for setups which don't involve flake-parts:

• set home-manager.useGlobalPkgs = false;
• in each user's home-manager module, add :

    nixpkgs = {
      config = lib.mapAttrs (n: v: lib.mkDefault v) osConfig.nixpkgs.config;
      # mkOrder 900 is after mkBefore but before default order
      overlays = lib.mkOrder 900 osConfig.nixpkgs.overlays;
    };

It silences the warning, but it really should be fixed in all upstreams projects.

[justDeeevin]

I'm very sorry i caused so much of a stirr with this change -- good learning experience to consider the impact of my code, i suppose

[brckd]

I'm very sorry i caused so much of a stirr with this change -- good learning experience to consider the impact of my code, i suppose

Don't worry, this was a learning experience for all of us. You fixed a bug which was clearly not intended and needed to be addressed. Although an intermediate warning would have been nice, this quickly urged configs and libraries to be updated, which was bound to happen sooner or later. Luckily it seems that pretty much only Stylix users were affected by this and it was all resolved within a day or two. But you're right, it really shows what unforeseen consequences a simple change can have!

[RossSmyth]

Yeah, how are you supposed to modify the nixpkgs config then? It would be good if that was documented somewhere. I got this for the allowUnfree config option which is pretty common to have set I believe.

[brckd]

@RossSmyth You're using useGlobalPkgs, which means that Home Manager will use the Nixpkgs instance NixOS uses. Therefore you have to move nixpkgs.allowUnfree and all your other Nixpkgs configurations into your NixOS module.