nixos/niri: add nautilus to systemPackages (#461501)

nixos/modules/programs/wayland/niri.nix

@@ -12,12 +12,22 @@ in
     enable = lib.mkEnableOption "Niri, a scrollable-tiling Wayland compositor";
 
     package = lib.mkPackageOption pkgs "niri" { };
+
+    useNautilus = lib.mkEnableOption "Nautilus as file-chooser for xdg-desktop-portal-gnome" // {
+      default = true;
+    };
   };
 
   config = lib.mkIf cfg.enable (
     lib.mkMerge [
       {
-        environment.systemPackages = [ cfg.package ];
+        environment.systemPackages = [
+          cfg.package
+        ]
+        # Required for xdg-desktop-portal-gnome's FileChooser to work properly
+        ++ lib.optionals cfg.useNautilus [
+          pkgs.nautilus
+        ];
 
         services = {
           displayManager.sessionPackages = [ cfg.package ];
@@ -34,6 +44,10 @@ in
 
           configPackages = [ cfg.package ];
 
+          config.niri = lib.mkIf (!cfg.useNautilus) {
+            "org.freedesktop.impl.portal.FileChooser" = lib.mkDefault "gtk";
+          };
+
           # Recommended by upstream, required for screencast support
           # https://github.com/YaLTeR/niri/wiki/Important-Software#portals
           extraPortals = [ pkgs.xdg-desktop-portal-gnome ];