sddm doesn't check if options make sense

[zeratax]

Describe the bug afaik wayland doesn't currently work with nvidia's propiertary drivers, yet when those are selected sddm still lets me create a gnome session with wayland, which then crashes, see https://github.com/NixOS/nixpkgs/issues/127501#issuecomment-864469906

Futhermore sddm doesn't seem to check if services.xserver.displayManager.defaultSession is correct, e.g. doesn't complain when the option is set to plasma instead of plasma5

is this an issue with sddm or just the display-manager module, since the assert is there? https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/services/x11/display-managers/default.nix#L271 gdm does complain about this

To Reproduce

1. configuration with:

   services.xserver.displayManager.sddm.enable = true;
   services.xserver.desktopManager.gnome.enable = true;
   services.xserver.displayManager.defaultSession = "plasma";
   services.xserver.videoDrivers = [ "nvidia" ]

2. rebuild system

Expected behavior rebuild gets cancelled and complains about "plasma" not being a proper value, instead showing which values are applicable. And sddm should not show Gnome (Wayland) as an option.

Additional context

Notify maintainers not sure?

Metadata

• system: "x86_64-linux"
• host os: Linux 5.10.43, NixOS, 21.05.1076.bad3ccd099e (Okapi)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3.12
• channels(root): "nixos-21.05.1076.bad3ccd099e, nixos-hardware, nixos-unstable-21.11p.fa0326ce523"
• channels(kaine): "home-manager"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute:
# a list of nixos modules affected by the problem
module:
  - services.sddm
  - services.xserver.displayManager

[stale[bot]]

I marked this as stale due to inactivity. → More info