refactor(nix): use pre-commit-hooks flake-parts module and treefmt

Author: justinrubek

flake-parts/devshell/default.nix

@@ -12,9 +12,7 @@
     inputs',
     self',
     ...
-  }: let
-    pre-commit-check = import ./pre_commit.nix inputs system;
-  in rec {
+  }: {
     devShells = {
       default = pkgs.mkShell {
         buildInputs = with pkgs; [
@@ -41,12 +39,11 @@
 
           inputs'.lockpad.packages.cli
         ];
-        inherit (pre-commit-check) shellHook;
-      };
-    };
 
-    checks = {
-      pre-commit = pre-commit-check;
+        shellHook = ''
+          ${config.pre-commit.installationScript}
+        '';
+      };
     };
   };
 }

flake-parts/devshell/pre_commit.nix

@@ -0,0 +1,31 @@
+{
+  inputs,
+  self,
+  ...
+}: {
+  perSystem = {
+    pkgs,
+    lib,
+    ...
+  }: let
+    formatters = [
+      pkgs.alejandra
+    ];
+
+    treefmt = pkgs.writeShellApplication {
+      name = "treefmt";
+      runtimeInputs = [pkgs.treefmt] ++ formatters;
+      text = ''
+        exec treefmt "$@"
+      '';
+    };
+  in {
+    packages = {
+      inherit treefmt;
+    };
+
+    legacyPackages = {
+      inherit formatters;
+    };
+  };
+}

flake-parts/formatting.nix

@@ -0,0 +1,21 @@
+{
+  inputs,
+  self,
+  ...
+}: {
+  perSystem = {self', ...}: let
+  in {
+    pre-commit = {
+      check.enable = true;
+
+      settings = {
+        src = ../.;
+        hooks = {
+          treefmt.enable = true;
+        };
+
+        settings.treefmt.package = self'.packages.treefmt;
+      };
+    };
+  };
+}

flake-parts/pre-commit.nix

@@ -116,6 +116,10 @@
         ./terraform/modules
 
         ./nomad
+
+        ./flake-parts/pre-commit.nix
+        ./flake-parts/formatting.nix
+        inputs.pre-commit-hooks.flakeModule
       ];
     };
 }

flake.nix

@@ -0,0 +1,3 @@
+[formatter.nix]
+command = "alejandra"
+includes = ["*.nix"]