@@ -7,94 +7,127 @@ inputs.gomod2nix.inputs.nixpkgs.follows = "nixpkgs";
   inputs.gomod2nix.inputs.flake-utils.follows = "utils";
   inputs.pre-commit-hooks.url = "github:cachix/pre-commit-hooks.nix";
   inputs.pre-commit-hooks.inputs.nixpkgs.follows = "nixpkgs";
+  inputs.treefmt-nix.url = "github:numtide/treefmt-nix";
 
-  outputs = { self, nixpkgs, utils, pre-commit-hooks, gomod2nix, ... }:
-    utils.lib.eachDefaultSystem
-      (system:
-        let
-          pkgs = import nixpkgs {
-            inherit system;
-            overlays = [
-              gomod2nix.overlays.default
-            ];
-          };
-          commonShellPackages = with pkgs; [
-            go
-            hyperlink
-            just
-            ko
-            flyctl
-            redis
-            sqlc
+  outputs =
+    {
+      self,
+      nixpkgs,
+      utils,
+      pre-commit-hooks,
+      gomod2nix,
+      treefmt-nix,
+      ...
+    }:
+    utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [
+            gomod2nix.overlays.default
           ];
-          devPackages = with pkgs; [
-            wgo
-            gopls
-            gotools
-            gomod2nix.legacyPackages.${system}.gomod2nix
+        };
+        commonShellPackages = with pkgs; [
+          go
+          hyperlink
+          just
+          ko
+          flyctl
+          redis
+          sqlc
+        ];
+        devPackages = with pkgs; [
+          wgo
+          gofumpt
+          gopls
+          gotools
+          gomod2nix.legacyPackages.${system}.gomod2nix
+          sqlfluff
 
-            systemfd
-            modd
-          ];
-        in
-        {
-          devShells = {
-            ci = pkgs.mkShell {
-              packages = commonShellPackages;
-            };
-            default = pkgs.mkShell {
-              inherit (self.checks.${system}.pre-commit-check) shellHook;
-              packages = devPackages ++ commonShellPackages;
-            };
+          systemfd
+          modd
+        ];
+        treefmtEval = treefmt-nix.lib.evalModule pkgs {
+          projectRootFile = "flake.nix";
+          programs = {
+            nixfmt.enable = true;
+            taplo.enable = true;
+            mdformat.enable = true;
+            gofumpt.enable = true;
+            golines.enable = true;
+            prettier.enable = true;
+            sqlfluff.enable = true;
+            sqlfluff.dialect = "sqlite";
+          };
+          settings = {
+            taplo.excludes = [ "gomod2nix.toml" ];
+          };
+        };
+      in
+      {
+        devShells = {
+          ci = pkgs.mkShell {
+            packages = commonShellPackages;
+          };
+          default = pkgs.mkShell {
+            inherit (self.checks.${system}.pre-commit-check) shellHook;
+            packages = devPackages ++ commonShellPackages;
           };
-          checks = {
-            pre-commit-check = pre-commit-hooks.lib.${system}.run {
-              src = ./.;
-              hooks = {
-                go-mod-tidy = {
-                  enable = true;
-                  name = "go-mod-tidy";
-                  description = "Run `go mod tidy`";
-                  types_or = [ "go" "go-mod" ];
-                  entry = "${pkgs.go}/bin/go mod tidy";
-                  pass_filenames = false;
-                };
-                golines.enable = true;
-                golangci-lint.enable = true;
-                gotest.enable = true;
-                govet.enable = true;
-                gomod2nix = {
-                  enable = true;
-                  name = "gomod2nix";
-                  description = "Import go.mod updates to nix";
-                  types_or = [ "go-sum" ];
-                  entry = "${pkgs.gomod2nix}/bin/gomod2nix";
-                  pass_filenames = false;
-                };
-                sqlc = {
-                  enable = true;
-                  name = "sqlc";
-                  description = "Generate go code from SQL";
-                  types_or = [ "sql" ];
-                  entry = "${pkgs.sqlc}/bin/sqlc generate";
-                  pass_filenames = false;
-                };
+        };
+        formatter = treefmtEval.config.build.wrapper;
+        checks = {
+          pre-commit-check = pre-commit-hooks.lib.${system}.run {
+            src = ./.;
+            hooks = {
+              go-mod-tidy = {
+                enable = true;
+                name = "go-mod-tidy";
+                description = "Run `go mod tidy`";
+                types_or = [
+                  "go"
+                  "go-mod"
+                ];
+                entry = "${pkgs.go}/bin/go mod tidy";
+                pass_filenames = false;
+              };
+              golines.enable = true;
+              golangci-lint.enable = true;
+              gotest.enable = true;
+              govet.enable = true;
+              gomod2nix = {
+                enable = true;
+                name = "gomod2nix";
+                description = "Import go.mod updates to nix";
+                types_or = [ "go-sum" ];
+                entry = "${pkgs.gomod2nix}/bin/gomod2nix";
+                pass_filenames = false;
+              };
+              sqlc = {
+                enable = true;
+                name = "sqlc";
+                description = "Generate go code from SQL";
+                types_or = [ "sql" ];
+                entry = "${pkgs.sqlc}/bin/sqlc generate";
+                pass_filenames = false;
               };
             };
           };
-          packages = {
-            build = pkgs.buildGoApplication {
-              pname = "build";
-              version = self.shortRev or self.dirtyShortRev;
-              src = ./.;
-              modules = ./gomod2nix.toml;
-              subPackages = [ "domain/content/builder/build" ];
-              nativeBuildInputs = with pkgs; [ makeWrapper ];
+        };
+        packages = {
+          build = pkgs.buildGoApplication {
+            pname = "build";
+            version = self.shortRev or self.dirtyShortRev;
+            src = ./.;
+            modules = ./gomod2nix.toml;
+            subPackages = [ "domain/content/builder/build" ];
+            nativeBuildInputs = with pkgs; [ makeWrapper ];
 
-              postInstall = ''
-                wrapProgram $out/bin/build --set KO_DATA_PATH ${./kodata}
-              '';
-            };
+            postInstall = ''
+              wrapProgram $out/bin/build --set KO_DATA_PATH ${./kodata}
+            '';
           };
-        });
+        };
+      }
+    );
 }