Use treefmt-nix

dev/treefmt.nix

@@ -0,0 +1,43 @@
+{ pkgs, lib, ... }: {
+  # Used to find the project root
+  projectRootFile = "flake.lock";
+
+  programs.prettier.enable = true;
+  programs.prettier.package = pkgs.writeShellScriptBin "prettier" ''
+    export NODE_PATH=${pkgs.nodePackages.prettier-plugin-toml}/lib/node_modules
+    exec ${lib.getExe pkgs.nodePackages.prettier} "$@"
+  '';
+
+  programs.clang-format.enable = true;
+
+  settings.formatter = {
+    nix = {
+      command = "sh";
+      options = [
+        "-eucx"
+        ''
+          ${pkgs.lib.getExe pkgs.nixpkgs-fmt} "$@"
+        ''
+        "--"
+      ];
+      includes = [ "*.nix" ];
+      excludes = [ ];
+    };
+
+    clang-format = { };
+
+    prettier.includes = lib.mkForce [ "*.toml" ];
+
+    python = {
+      command = "sh";
+      options = [
+        "-eucx"
+        ''
+          ${pkgs.lib.getExe pkgs.python3.pkgs.black} "$@"
+        ''
+        "--" # this argument is ignored by bash
+      ];
+      includes = [ "*.py" ];
+    };
+  };
+}

flake.lock

@@ -39,7 +39,28 @@
     "root": {
       "inputs": {
         "flake-parts": "flake-parts",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "treefmt-nix": "treefmt-nix"
+      }
+    },
+    "treefmt-nix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1689620039,
+        "narHash": "sha256-BtNwghr05z7k5YMdq+6nbue+nEalvDepuA7qdQMAKoQ=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "719c2977f958c41fa60a928e2fbc50af14844114",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
       }
     }
   },

flake.nix

@@ -4,6 +4,8 @@
   inputs.nixpkgs.url = "github:NixOS/nixpkgs/master";
   inputs.flake-parts.url = "github:hercules-ci/flake-parts";
   inputs.flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";
+  inputs.treefmt-nix.url = "github:numtide/treefmt-nix";
+  inputs.treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
 
   nixConfig.extra-substituters = [
     "https://cache.garnix.io"
@@ -21,6 +23,7 @@
     flake-parts.lib.mkFlake { inherit inputs; }
       {
         systems = inputs.nixpkgs.lib.systems.flakeExposed;
+        imports = [ inputs.treefmt-nix.flakeModule ];
         perSystem = { pkgs, self', ... }:
           let
             devShell = self'.devShells.default;
@@ -30,24 +33,9 @@
             };
           in
           {
+            treefmt.imports = [ ./dev/treefmt.nix ];
             packages.nix-eval-jobs = pkgs.callPackage ./default.nix drvArgs;
             packages.clangStdenv-nix-eval-jobs = pkgs.callPackage ./default.nix (drvArgs // { stdenv = pkgs.clangStdenv; });
-
-            checks.treefmt = pkgs.stdenv.mkDerivation {
-              name = "treefmt-check";
-              src = self;
-              nativeBuildInputs = devShell.nativeBuildInputs;
-              dontConfigure = true;
-
-              inherit (devShell) NODE_PATH;
-
-              buildPhase = ''
-                env HOME=$(mktemp -d) treefmt --fail-on-change
-              '';
-
-              installPhase = "touch $out";
-            };
-
             packages.default = self'.packages.nix-eval-jobs;
             devShells.default = pkgs.callPackage ./shell.nix drvArgs;
           };

shell.nix

@@ -23,18 +23,11 @@ in
 pkgs.mkShell {
   inherit (nix-eval-jobs) buildInputs;
   nativeBuildInputs = nix-eval-jobs.nativeBuildInputs ++ [
-    pkgs.treefmt
-    pkgs.llvmPackages.clang # clang-format
-    pkgs.nixpkgs-fmt
-    pkgs.nodePackages.prettier
-
     (pkgs.python3.withPackages (ps: [
       ps.pytest
-      ps.black
     ]))
 
   ];
-  NODE_PATH = "${pkgs.nodePackages.prettier-plugin-toml}/lib/node_modules";
 
   shellHook = lib.optionalString stdenv.isLinux ''
     export NIX_DEBUG_INFO_DIRS="${pkgs.curl.debug}/lib/debug:${nix.debug}/lib/debug''${NIX_DEBUG_INFO_DIRS:+:$NIX_DEBUG_INFO_DIRS}"

treefmt.toml

@@ -1,17 +0,0 @@
-[formatter."c++"]
-command = "clang-format"
-options = ["-i"]
-includes = ["*.c", "*.cpp", "*.cc", "*.h", "*.hpp"]
-
-[formatter.nix]
-command = "nixpkgs-fmt"
-includes = ["*.nix"]
-
-[formatter.toml]
-command = "prettier"
-options = ["--write"]
-includes = ["*.toml"]
-
-[formatter.python]
-command = "black"
-includes = ["*.py"]