blender: add CUDA discovery test

pkgs/applications/misc/blender/default.nix

@@ -372,6 +372,16 @@ stdenv.mkDerivation (finalAttrs: {
             --render-frame 1
         done
       '';
+
+      cudaAvailable = runCommand
+      "blender-cuda-available"
+      {
+        nativeBuildInputs = [ finalAttrs.finalPackage ];
+        requiredSystemFeatures = [ "cuda" ];
+      }
+      ''
+        blender --background -noaudio --python-exit-code 1 --python ${./test-cuda.py} && touch $out
+      '';
     };
   };
 

pkgs/applications/misc/blender/test-cuda.py

@@ -0,0 +1,8 @@
+import bpy
+
+preferences = bpy.context.preferences.addons["cycles"].preferences
+devices = preferences.get_devices_for_type("CUDA")
+ids = [d.id for d in devices]
+
+assert any("CUDA" in i for i in ids), f"CUDA not present in {ids}"
+print("CUDA is available")