nix: Add overlay to HM module + useful script

nix/module.nix

@@ -7,7 +7,7 @@ let
   jsonFormat = pkgs.formats.json { };
   
   # No package option
-  package = self.packages.${pkgs.system}.default;
+  package = pkgs.hyprpanel;
 
   # Shorthand lambda for self-documenting options under settings
   mkStrOption = default: mkOption { type = types.str; default = default; };
@@ -43,14 +43,14 @@ let
         let
           items = builtins.map toNestedValue value;
         in
-          "[" + (builtins.concatStringsSep ", " items) + "]"
+          "[\n" + (builtins.concatStringsSep ", " items) + "\n]"
       else if builtins.isAttrs value then
         let
           keys = builtins.attrNames value;
           toKeyValue = k: "\"${k}\": ${toNestedValue value.${k}}";
           inner = builtins.concatStringsSep ", " (builtins.map toKeyValue keys);
         in
-          "{ " + inner + " }"
+          "{\n" + inner + "\n}"
       else
         abort "Unexpected error! Please post a new issue and @benvonh...";
 
@@ -59,7 +59,7 @@ let
       keys = builtins.attrNames attrSet;
       kvPairs = builtins.map (k: "\"${k}\": ${toNestedValue attrSet.${k}}") keys;
     in
-      "{ " + builtins.concatStringsSep ", " kvPairs + " }";
+      "{\n  " + builtins.concatStringsSep ",\n  " kvPairs + "\n}";
 in
 {
   options.programs.hyprpanel = {
@@ -547,9 +547,40 @@ in
     };
   };
 
-  config = mkIf cfg.enable {
+  config = let
+
+    theme = if cfg.theme != ""
+      then builtins.fromJSON (builtins.readFile ../themes/${cfg.theme}.json)
+      else {};
+
+    flatSet = flattenAttrs (lib.attrsets.recursiveUpdate cfg.settings theme) "";
+
+    mergeSet = flatSet // (flattenAttrs cfg.override "");
+
+    fullSet = if cfg.layout == null then mergeSet else mergeSet // cfg.layout;
+
+    finalConfig = toNestedObject fullSet;
+
+    hyprpanel-diff = pkgs.writeShellApplication {
+      runtimeInputs = [ pkgs.colordiff ];
+      name = "hyprpanel-diff";
+      text = ''
+        cd
+        echo '------------- HyprPanel -------------'
+        echo 'Please ignore the layout diff for now'
+        echo '-------------------------------------'
+        colordiff ${config.xdg.configFile.hyprpanel.target} \
+                  ${config.xdg.configFile.hyprpanel-swap.target}
+      '';
+    };
+
+  in mkIf cfg.enable {
+
+    nixpkgs.overlays = [ self.overlay ];
+
     home.packages = [
       package
+      hyprpanel-diff
       (if pkgs ? nerd-fonts.jetbrains-mono
       then pkgs.nerd-fonts.jetbrains-mono
       # NOTE:(benvonh) Remove after next release 25.05
@@ -569,19 +600,17 @@ in
         '';
       };
 
-    xdg.configFile.hyprpanel = let
-      theme = if cfg.theme != ""
-        then builtins.fromJSON (builtins.readFile ../themes/${cfg.theme}.json)
-        else {};
-      flatSet = flattenAttrs (lib.attrsets.recursiveUpdate cfg.settings theme) "";
-      mergeSet = flatSet // (flattenAttrs cfg.override "");
-      fullSet = if cfg.layout == null then mergeSet else mergeSet // cfg.layout;
-    in {
+    xdg.configFile.hyprpanel = {
       target = "hyprpanel/config.json";
-      text = toNestedObject fullSet;
+      text = finalConfig;
       onChange = "${pkgs.procps}/bin/pkill -u $USER -USR1 hyprpanel || true";
     };
 
+    xdg.configFile.hyprpanel-swap = {
+      target = "hyprpanel/config.hm.json";
+      text = finalConfig;
+    };
+
     systemd.user.services = mkIf cfg.systemd.enable {
       hyprpanel = {
         Unit = {