modules: system: nix: make it configurable

modules/system/nix.nix

@@ -1,19 +1,35 @@
 # Nix related settings
-{ inputs, pkgs, ... }:
-
+{ config, inputs, lib, pkgs, ... }:
+let
+  cfg = config.my.system.nix;
+in
 {
-  nix = {
-    package = pkgs.nixFlakes;
-    registry = {
-      # Allow me to use my custom package using `nix run self#pkg`
-      self.flake = inputs.self;
-      # Use pinned nixpkgs when using `nix run pkgs#<whatever>`
-      pkgs.flake = inputs.nixpkgs;
-      # Add NUR to run some packages that are only present there
-      nur.flake = inputs.nur;
-    };
-    extraOptions = ''
-      experimental-features = nix-command flakes
-    '';
+  options.my.system.nix = with lib; {
+    enable = my.mkDisableOption "nix configuration";
+
+    addToRegistry = my.mkDisableOption "add inputs and self to registry";
   };
+
+  config = lib.mkIf cfg.enable (lib.mkMerge [
+    {
+      nix = {
+        package = pkgs.nixFlakes;
+
+        extraOptions = ''
+          experimental-features = nix-command flakes
+        '';
+      };
+    }
+
+    (lib.mkIf cfg.addToRegistry {
+      nix.registry = {
+        # Allow me to use my custom package using `nix run self#pkg`
+        self.flake = inputs.self;
+        # Use pinned nixpkgs when using `nix run pkgs#<whatever>`
+        pkgs.flake = inputs.nixpkgs;
+        # Add NUR to run some packages that are only present there
+        nur.flake = inputs.nur;
+      };
+    })
+  ]);
 }