assertions

modules/nixos/home/default.nix

@@ -36,6 +36,30 @@ in
   };
 
   config = {
+    assertions =
+      let
+        desktopCount = lib.count lib.id [
+          config.${namespace}.desktop.gnome.enable
+          config.${namespace}.desktop.hyprland.enable
+          config.${namespace}.desktop.cosmic.enable
+        ];
+      in
+      [
+        {
+          assertion = desktopCount <= 1;
+          message = ''
+            At most one desktop environment may be enabled simultaneously.
+            Currently enabled: ${
+              lib.concatStringsSep ", " (
+                lib.optional config.${namespace}.desktop.gnome.enable "gnome"
+                ++ lib.optional config.${namespace}.desktop.hyprland.enable "hyprland"
+                ++ lib.optional config.${namespace}.desktop.cosmic.enable "cosmic"
+              )
+            }.
+          '';
+        }
+      ];
+
     # ${namespace}.home.extraOptions = {
     #   home.file = lib.mkAliasDefinitions options.${namespace}.home.file;
     #   home.stateVersion = lib.mkOptionDefault config.system.stateVersion;