add treefmt-nix configuration

README.md

@@ -2,6 +2,7 @@
 
 A nixos module to make buildbot a proper Nix-CI.
 
-For an example checkout the [example](./examples/default.nix) and the module descriptions for [master](./nix/master.nix) and [worker](./nix/worker.nix).
+For an example checkout the [example](./examples/default.nix) and the module
+descriptions for [master](./nix/master.nix) and [worker](./nix/worker.nix).
 
 This project is still in early stage and many APIs might change over time.

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": 1694528738,
+        "narHash": "sha256-aWMEjib5oTqEzF9f3WXffC1cwICo6v/4dYKjwNktV8k=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "7a49c388d7a6b63bb551b1ddedfa4efab8f400d8",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
       }
     }
   },

nix/treefmt/flake-module.nix

@@ -0,0 +1,29 @@
+{ inputs, ... }: {
+  imports = [
+    inputs.treefmt-nix.flakeModule
+  ];
+  perSystem = { config, pkgs, ... }: {
+    treefmt = {
+      projectRootFile = ".git/config";
+      programs.nixpkgs-fmt.enable = true;
+      programs.shellcheck.enable = true;
+      programs.deno.enable = true;
+      settings.formatter.shellcheck.options = [ "-s" "bash" ];
+
+      programs.mypy.enable = true;
+      programs.mypy.directories."." = { };
+      settings.formatter.python = {
+        command = "sh";
+        options = [
+          "-eucx"
+          ''
+            ${pkgs.ruff}/bin/ruff --fix "$@"
+            ${pkgs.python3.pkgs.black}/bin/black "$@"
+          ''
+          "--" # this argument is ignored by bash
+        ];
+        includes = [ "*.py" ];
+      };
+    };
+  };
+}