try fufexans git hooks setup

.gitignore

@@ -1,2 +1,3 @@
 .direnv
+.pre-commit-config.yaml
 result*

flake.nix

@@ -9,6 +9,7 @@
         ./users
         ./hosts
         ./modules
+        ./fmt-hooks.nix
       ];
 
       perSystem = {pkgs, ...}: {
@@ -105,6 +106,19 @@
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
+    git-hooks = {
+      url = "github:cachix/git-hooks.nix";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+        flake-compat.follows = "flake-compat";
+      };
+    };
+
+    treefmt-nix = {
+      url = "github:numtide/treefmt-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+
     # Custom
     tuirun = {
       url = "git+https://git.sr.ht/~canasta/tuirun";

fmt-hooks.nix

@@ -0,0 +1,26 @@
+{inputs, ...}: {
+  imports = [
+    inputs.git-hooks.flakeModule
+    inputs.treefmt-nix.flakeModule
+  ];
+
+  perSystem = {
+    pre-commit.settings = {
+      excludes = ["flake.lock"];
+      hooks.treefmt.enable = true;
+    };
+
+    treefmt.programs = {
+      nixfmt.enable = true;
+
+      prettier = {
+        enable = true;
+        excludes = [
+          ".js"
+          ".md"
+          ".ts"
+        ];
+      };
+    };
+  };
+}

modules/home/programs/helix/languages.nix

@@ -79,7 +79,7 @@
           auto-format = true;
           language-servers = ["nil"];
           formatter = {
-            command = "${pkgs.alejandra}/bin/alejandra";
+            command = "${pkgs.nixfmt}/bin/nixfmt";
             args = ["-q"];
           };
         }