Rebuilding NixOS on Raspberry Pi 4 fails after commit 4014fb6

[superherointj]

Rebuilding NixOS on Raspberry Pi 4 fails after commit: 4014fb6 (PR #151082)

Errors as:

/nix/store/l3lj95gg3fx9amqcywv0qfsabs2nw4nj-raspberrypi-builder.sh: illegal option -- g
usage: /nix/store/l3lj95gg3fx9amqcywv0qfsabs2nw4nj-raspberrypi-builder.sh -c <path-to-default-configuration> [-d <boot-dir>]
warning: error(s) occurred while switching to the new configuration

My configuration.nix has:

boot.loader.raspberryPi = {
  enable = true;
  version = 4;
  firmwareConfig = ''
    dtparam=sd_poll_once=on
    dtoverlay=vc4_fkms_v3d,cma-256
  '';
};

boot.loader.generic-extlinux-compatible.enable = true;

system.stateVersion = "21.11";

Question:

1. Does it affect other Raspberry Pi 4 users (when upgrading past PR nixos: turn vmWithBootLoader into option (nixos-rebuild build-vm) #151082)?

@roberth @ncfavier @samueldr

[rhoriguchi]

Might be able to help: @samueldr @tkerber

[ncfavier]

I think the problem is that the new type causes multiple definitions to be merged (concatenated as strings), and since you're probably generating an SD image your config has boot.loader.generic-extlinux-compatible.enable = true which results in two definitions for system.build.installBootLoader, one from raspberrypi.nix and one from generic-extlinux-compatible (notice the -g there in builderArgs), so the resulting builder is nonsense.

Now I wonder why this succeeded before this commit. EDIT: it's because type.attrs merges with //, and in this case the extlinux definition was winning.

[superherointj]

I think the problem is that the new type causes multiple definitions to be merged (concatenated as strings), and since you're probably generating an SD image your config has boot.loader.generic-extlinux-compatible.enable = true which results in two definitions for system.build.installBootLoader, one from raspberrypi.nix and one from generic-extlinux-compatible (notice the -g there in builderArgs), so the resulting builder is nonsense.

Now I wonder why this succeeded before this commit.

Correct, my configuration.nix has:
boot.loader.generic-extlinux-compatible.enable = true

[superherointj]

As @ncfavier correctly pointed out: The configs were clashing and that was causing the issue. After fixing the configuration.nix (by removing the raspberryPi specific config) I'm now able to upgrade past commit 4014fb6 to unstable. So I'm closing the issue.

Thanks @samueldr @ncfavier for the support in solving this issue.