nixos/desktopManager: Only trace if the default session isn't found

The default session might be found in `extraSessionFilePackages`, but it's not
viable to detect at evaluation time, so emit a warning.

In LightDM instead of checking `defaultSessionName` against
`displayManager.session.names` we rely on the assertions in
`desktopManager` and `windowMananger` and just check that there's at least one
default set. The second assertion could never actually be triggered.

1 files changed, 1 insertions, 9 deletions

diff --git a/nixos/modules/services/x11/display-managers/lightdm.nix b/nixos/modules/services/x11/display-managers/lightdm.nix
index 9b5f51fb4cf..6be15d8cdf4 100644
--- a/nixos/modules/services/x11/display-managers/lightdm.nix
+++ b/nixos/modules/services/x11/display-managers/lightdm.nix
@@ -176,21 +176,13 @@ in
           LightDM auto-login requires services.xserver.displayManager.lightdm.autoLogin.user to be set
         '';
       }
-      { assertion = cfg.autoLogin.enable -> elem defaultSessionName dmcfg.session.names;
+      { assertion = cfg.autoLogin.enable -> dmDefault != "none" || wmDefault != "none";
         message = ''
           LightDM auto-login requires that services.xserver.desktopManager.default and
           services.xserver.windowMananger.default are set to valid values. The current
           default session: ${defaultSessionName} is not valid.
         '';
       }
-      { assertion = hasDefaultUserSession -> elem defaultSessionName dmcfg.session.names;
-        message = ''
-          services.xserver.desktopManager.default and
-          services.xserver.windowMananger.default are not set to valid
-          values. The current default session: ${defaultSessionName}
-          is not valid.
-        '';
-      }
       { assertion = !cfg.greeter.enable -> (cfg.autoLogin.enable && cfg.autoLogin.timeout == 0);
         message = ''
           LightDM can only run without greeter if automatic login is enabled and the timeout for it