From 105fdc89ac4fd6892c14e8dc57b3d9eee666544d Mon Sep 17 00:00:00 2001
From: Sridhar Ratnakumar <srid@srid.ca>
Date: Fri, 3 Jan 2025 13:24:11 -0500
Subject: [PATCH] nix: treefmt -> git-hooks.nix

---
 .gitignore |  3 ++-
 flake.lock | 40 ++++++++++++++++++----------------------
 flake.nix  | 32 +++++++++++++++-----------------
 3 files changed, 35 insertions(+), 40 deletions(-)

diff --git a/.gitignore b/.gitignore
index 54ffe60..ab2b6a9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -24,4 +24,5 @@ cabal.project.local~
 result
 result-*
 
-.direnv
\ No newline at end of file
+.direnv
+/.pre-commit-config.yaml
\ No newline at end of file
diff --git a/flake.lock b/flake.lock
index 102858e..ef1aee9 100644
--- a/flake.lock
+++ b/flake.lock
@@ -243,6 +243,22 @@
         "type": "github"
       }
     },
+    "git-hooks": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1735882644,
+        "narHash": "sha256-3FZAG+pGt3OElQjesCAWeMkQ7C/nB1oTHLRQ8ceP110=",
+        "owner": "cachix",
+        "repo": "git-hooks.nix",
+        "rev": "a5a961387e75ae44cc20f0a57ae463da5e959656",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "git-hooks.nix",
+        "type": "github"
+      }
+    },
     "haskell-flake": {
       "locked": {
         "lastModified": 1709233214,
@@ -420,11 +436,11 @@
         "ema": "ema",
         "flake-parts": "flake-parts_3",
         "fourmolu-nix": "fourmolu-nix",
+        "git-hooks": "git-hooks",
         "haskell-flake": "haskell-flake_3",
         "nixpkgs": "nixpkgs_3",
         "process-compose-flake": "process-compose-flake",
-        "systems": "systems_2",
-        "treefmt-nix": "treefmt-nix_3"
+        "systems": "systems_2"
       }
     },
     "systems": {
@@ -497,26 +513,6 @@
         "type": "github"
       }
     },
-    "treefmt-nix_3": {
-      "inputs": {
-        "nixpkgs": [
-          "nixpkgs"
-        ]
-      },
-      "locked": {
-        "lastModified": 1735905407,
-        "narHash": "sha256-1hKMRIT+QZNWX46e4gIovoQ7H8QRb7803ZH4qSKI45o=",
-        "owner": "numtide",
-        "repo": "treefmt-nix",
-        "rev": "29806abab803e498df96d82dd6f34b32eb8dd2c8",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "treefmt-nix",
-        "type": "github"
-      }
-    },
     "unionmount": {
       "flake": false,
       "locked": {
diff --git a/flake.nix b/flake.nix
index b16f906..43b0cad 100644
--- a/flake.nix
+++ b/flake.nix
@@ -7,9 +7,9 @@
     haskell-flake.url = "github:srid/haskell-flake";
 
     process-compose-flake.url = "github:Platonic-Systems/process-compose-flake";
-    treefmt-nix.url = "github:numtide/treefmt-nix";
-    treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
     fourmolu-nix.url = "github:jedimahdi/fourmolu-nix";
+    git-hooks.url = "github:cachix/git-hooks.nix";
+    git-hooks.flake = false;
 
     ema.url = "github:srid/ema";
     ema.inputs.nixpkgs.follows = "nixpkgs";
@@ -20,10 +20,10 @@
       imports = [
         inputs.haskell-flake.flakeModule
         inputs.process-compose-flake.flakeModule
-        inputs.treefmt-nix.flakeModule
         inputs.fourmolu-nix.flakeModule
+        (inputs.git-hooks + /flake-module.nix)
       ];
-      perSystem = { config, self', pkgs, lib, ... }:
+      perSystem = { config, pkgs, lib, ... }:
         let
           tailwind = pkgs.haskellPackages.tailwind;
         in
@@ -36,18 +36,16 @@
             autoWire = [ "packages" "apps" "checks" ];
           };
 
-          # Auto formatters. This also adds a flake check to ensure that the
-          # source tree was auto formatted.
-          treefmt.config = {
-            projectRootFile = "flake.nix";
-
-            programs.fourmolu.enable = true;
-            programs.nixpkgs-fmt.enable = true;
-            programs.cabal-fmt.enable = true;
-            programs.hlint.enable = true;
-
-            # We use fourmolu
-            programs.fourmolu.package = config.fourmolu.wrapper;
+          pre-commit.settings = {
+            hooks = {
+              nixpkgs-fmt.enable = true;
+              cabal-fmt.enable = true;
+              fourmolu = {
+                enable = true;
+                package = config.fourmolu.wrapper;
+              };
+              hlint.enable = true;
+            };
           };
 
           fourmolu.settings = {
@@ -105,7 +103,7 @@
             ];
             inputsFrom = [
               config.haskellProjects.default.outputs.devShell
-              config.treefmt.build.devShell
+              config.pre-commit.devShell
             ];
           };
         };