xdg-autostart: allow empty readonly autostart

Create the readonly autostart link even when no managed entries are
present, so the option behavior matches its documentation and stays
covered by a focused regression test.

modules/misc/xdg-autostart.nix

@@ -51,7 +51,7 @@ in
     };
   };
 
-  config = mkIf (cfg.enable && cfg.entries != [ ]) {
+  config = mkIf (cfg.enable && (cfg.readOnly || cfg.entries != [ ])) {
     xdg.configFile.autostart = {
       source = linkedDesktopEntries;
       recursive = !cfg.readOnly;

tests/modules/misc/xdg/autostart-readonly-empty.nix

@@ -0,0 +1,10 @@
+{
+  xdg.autostart = {
+    enable = true;
+    readOnly = true;
+  };
+
+  nmt.script = ''
+    assertLinkExists home-files/.config/autostart
+  '';
+}

tests/modules/misc/xdg/default.nix

@@ -4,6 +4,7 @@
   xdg-mime-disabled = ./mime-disabled.nix;
   xdg-autostart = ./autostart.nix;
   xdg-autostart-readonly = ./autostart-readonly.nix;
+  xdg-autostart-readonly-empty = ./autostart-readonly-empty.nix;
   xdg-local-bin-in-path = ./local-bin-in-path.nix;
   xdg-local-bin-not-in-path = ./local-bin-not-in-path.nix;
   xdg-user-dirs-mixed = ./user-dirs-mixed.nix;