Get system from pkgs.stdenv.hostPlatform...

[phaer]

...instead of config.nixpkgs.

Without this, I encountered the following error while evaluating a host that includes typhons nixOS module.

error: Neither nixpkgs.system nor any other option in nixpkgs.* is meant to be read by modules and configurations.
Use pkgs.stdenv.hostPlatform instead.

[pnmadelaine]

what version of nixpkgs are you using? 🤔

[phaer]

nixos-unstable, resolved to NixOS/nixpkgs@b98a4e1 at last lock.

[pnmadelaine]

I don't understand how we have not yet run into this error, either in the NixOS test or when deploying etna.typhon-ci.org (which is coincidently down for unrelated reasons).

The situation is pretty clear when reading the error message which was introduced in NixOS/nixpkgs@acd969a, so this looks like a necessary patch.

Still, I would really like to understand how on earth I am unable to reproduce the error!

[phaer]

Running a bit short on time atm, but my first guess would be that it could be related to how lib.nixosSystem gets called?

[phaer]

@pnmadelaine So, it should be reproducible if you call lib.nixosSystem without a system argument, but set nixpkgs.hostPlatform.

Reproducer

{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
    typhon.url = "github:typhon-ci/typhon";
  };

  outputs = { self, nixpkgs, typhon }: {
    nixosConfigurations.example = nixpkgs.lib.nixosSystem {
      modules = [
        typhon.nixosModules.default
        ({modulesPath, ...}: {
          imports = [
            "${modulesPath}/profiles/minimal.nix"
          ];
          config = {
            boot.isContainer = true;
            nixpkgs.hostPlatform = "x86_64-linux";

            services.typhon.enable = true;
            services.typhon.hashedPasswordFile = "/dev/null";
          };
        })
      ];
    };
  };
}

[pnmadelaine]

it could be related to how lib.nixosSystem gets called?

Right, I always call lib.nixosSystem with the system argument, which seems to avoid the error as it overrides config.nixpkgs.system. I suppose @W95Psp is doing the same in the configuration for Etna… I guess we should stop doing that? 🤔 Feels weird since it sounds a lot more straightforward than setting the system via a module like you do in your example…

Anyway thank you for the patch! I will merge it as soon as our CI is back online 😄

[phaer]

Feels weird since it sounds a lot more straightforward than setting the system via a module like you do in your example…

My motivation for doing so, is that I can use the same lib.nixosSystem call for all hosts and just pass a set of modules into it. My host-specific configuration is just another module, where one of them defines the host platform (i have both, x86_64-linux and aarch64-linux machines in .#nixosConfigurations.