Novice question: debugging a package fix: can I locally override just a single line of a long multi-line string in a package?

[jtojnar]

@qsu

1. git checkout 22.05 (as that is what’s in my system’s file’s system.stateVersion value)

stateVersion has little to do with what version of Nixpkgs are you using. It is really just to make sure NixOS modules for stateful programs can evolve without breaking existing systems on updates.

And 22.05 is actually a git tag that points to the state of the Nixpkgs repo at the time NixOS 22.05 was released so I hope you are not using it on your system – you would be missing almost two years of updates.

You can get the version of your system using nixos-version:

$ nixos-version
24.05.20240102.bd645e8 (Uakari)

For example bd645e8 is the commit id in my case.

You can checkout that commit, or the branch corresponding to the NixOS channel you use:

• nixos-unstable for unstable
• release-23.11 for stable

You can find the channel using sudo nix-channel --list (if you use Flakes, look into the inputs section of. flake.nix). You will also see the branch if you open the commit on GitHub.

@qsu

4. now try to reproduce the error by getting installPhase to execute…

   • Reading the nixos-rebuild manpage I think build-vm would be nice or even test (so I don’t add another boot entry for this tinkering). I’ve tried both:

     • nixos-rebuild --show-trace build-vm -I nixpkgs="$PWD"
     • nixos-rebuild --show-trace test -I nixpkgs="$PWD"

   • both of those^ commands result all sorts of lines of my /etc/nixos/*.nix files having issues. Issues I don’t see day to day when I run nixos-rebuild switch on a regular basis (just managing personal package selections). here’s a snippet of the error:

     error: The option `fonts.enableDefaultPackages' does not exist. Definition values:
      - In `/etc/nixos/configuration.nix': true
     

That sounds like it might just be incompatibility because of too old Nixpkgs revision.