nixos/nix-required-mounts: fix infinite recursion with userborn (#488199)

nixos/modules/programs/nix-required-mounts.nix

@@ -47,10 +47,7 @@ let
     );
 
   driverPaths = [
-    # opengl:
-    # NOTE: Since driverLink is just a symlink, we need to include its target as well.
     pkgs.addDriverRunpath.driverLink
-    config.systemd.tmpfiles.settings.graphics-driver."/run/opengl-driver"."L+".argument
 
     # mesa:
     config.hardware.graphics.package
@@ -62,7 +59,9 @@ let
   defaults = {
     nvidia-gpu.onFeatures = package.allowedPatterns.nvidia-gpu.onFeatures;
     nvidia-gpu.paths = package.allowedPatterns.nvidia-gpu.paths ++ driverPaths;
-    nvidia-gpu.unsafeFollowSymlinks = false;
+    # TODO: Refactor `hardware.graphics` to ease referencing the closure
+    # NOTE: A naive implementation may e.g. introduce a conditional infinite recursion (https://github.com/NixOS/nixpkgs/pull/488199)
+    nvidia-gpu.unsafeFollowSymlinks = true;
   };
 in
 {
@@ -112,6 +111,7 @@ in
     lib.mkMerge [
       { nix.settings.pre-build-hook = lib.getExe cfg.package; }
       (lib.mkIf cfg.presets.nvidia-gpu.enable {
+        hardware.graphics.enable = lib.mkDefault true;
         nix.settings.system-features = cfg.allowedPatterns.nvidia-gpu.onFeatures;
         programs.nix-required-mounts.allowedPatterns = {
           inherit (defaults) nvidia-gpu;

pkgs/by-name/ni/nix-required-mounts/eval-test.nix

@@ -0,0 +1,26 @@
+{
+  nixos,
+  lib,
+  runCommand,
+}:
+let
+  base = nixos {
+    services.userborn.enable = true;
+    programs.nix-required-mounts = {
+      enable = true;
+      presets.nvidia-gpu.enable = true;
+    };
+    fileSystems."/".device = "/dev/null";
+    boot.loader.grub.enable = false;
+    system.stateVersion = lib.trivial.release;
+  };
+  machine = base.extendModules {
+    modules = [ { hardware.graphics.enable = true; } ];
+  };
+in
+runCommand "nix-required-mounts-eval-nvidia-gpu-preset" { } ''
+  echo "Successfully evaluated ${base.config.system.build.toplevel}"
+  echo "Successfully evaluated ${machine.config.system.build.toplevel}"
+  echo "This means that combining nix-required-mounts with userborn no longer causes infinite recursion (#488199)"
+  touch $out
+''

pkgs/by-name/ni/nix-required-mounts/package.nix

@@ -55,6 +55,7 @@ python3Packages.buildPythonApplication {
     inherit allowedPatterns;
     tests = {
       inherit (nixosTests) nix-required-mounts;
+      eval-nvidia-gpu-preset = callPackage ./eval-test.nix { };
     };
   };
   meta = {