@@ -15,52 +15,81 @@ nixpkgs.follows = "nixpkgs";
         flake-utils.follows = "flake-utils";
       };
     };
+    treefmt-nix.url = "github:numtide/treefmt-nix";
     simple-css = {
       url = "https://raw.githubusercontent.com/kevquirk/simple.css/v2.3.4/simple.css";
       flake = false;
     };
   };
 
-  outputs = { self, nixpkgs, flake-utils, gomod2nix, pre-commit-hooks, simple-css }:
+  outputs =
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+      gomod2nix,
+      pre-commit-hooks,
+      treefmt-nix,
+      simple-css,
+    }:
     {
       nixosModules = {
         web = import ./nix/modules self;
       };
-    } // (flake-utils.lib.eachDefaultSystem
-      (system:
-        let
-          pkgs = import nixpkgs {
-            inherit system;
-            overlays = [
-              (import ./nix/overlays)
-              gomod2nix.overlays.default
-            ];
+    }
+    // (flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [
+            (import ./nix/overlays)
+            gomod2nix.overlays.default
+          ];
+        };
+
+        treefmtEval = treefmt-nix.lib.evalModule pkgs {
+          projectRootFile = "flake.nix";
+          programs = {
+            nixfmt.enable = true;
+            taplo.enable = true;
+            prettier.enable = true;
+            gofumpt.enable = true;
+            golines.enable = true;
+            sqlfluff.enable = true;
+            sqlfluff.dialect = "sqlite";
           };
-        in
-        rec {
-          packages.css = "${simple-css}";
-          packages.default = pkgs.callPackage ./nix/package.nix {
-            inherit (gomod2nix.legacyPackages.${system}) buildGoApplication;
-            css = simple-css;
+          settings.formatter = {
+            taplo.excludes = [ "gomod2nix.toml" ];
           };
-          devShells.default = pkgs.callPackage ./nix/dev-shell.nix {
-            pre-commit-check = {
-              inherit (self.checks.${system}.pre-commit-check)
-                shellHook
-                enabledPackages;
-            };
-            inherit (gomod2nix.legacyPackages.${system}) mkGoEnv gomod2nix;
+        };
+      in
+      rec {
+        packages.css = "${simple-css}";
+        packages.default = pkgs.callPackage ./nix/package.nix {
+          inherit (gomod2nix.legacyPackages.${system}) buildGoApplication;
+          css = simple-css;
+        };
+        formatter = treefmtEval.config.build.wrapper;
+        devShells.default = pkgs.callPackage ./nix/dev-shell.nix {
+          pre-commit-check = {
+            inherit (self.checks.${system}.pre-commit-check)
+              shellHook
+              enabledPackages
+              ;
           };
-          checks = {
-            pre-commit-check = pre-commit-hooks.lib.${system}.run (
-              import ./nix/pre-commit-checks.nix {
-                inherit pkgs;
-              }
-            );
-            buildVersion = pkgs.testers.testVersion {
-              package = packages.default;
-            };
+          inherit (gomod2nix.legacyPackages.${system}) mkGoEnv gomod2nix;
+        };
+        checks = {
+          pre-commit-check = pre-commit-hooks.lib.${system}.run (
+            import ./nix/pre-commit-checks.nix {
+              inherit pkgs treefmtEval;
+            }
+          );
+          buildVersion = pkgs.testers.testVersion {
+            package = packages.default;
           };
-        })
-    );
+        };
+      }
+    ));
 }