add formatter for python

Author: Mic92

treefmt/flake-module.nix

@@ -2,7 +2,7 @@
   imports = [
     inputs.treefmt-nix.flakeModule
   ];
-  perSystem = { config, ... }: {
+  perSystem = { config, lib, pkgs, ... }: {
     treefmt = {
       projectRootFile = "flake.nix";
       programs.mdsh.enable = true;
@@ -11,6 +11,18 @@
       programs.shfmt.enable = true;
       programs.deno.enable = true;
       settings.formatter.shellcheck.options = [ "-s" "bash" ];
+      settings.formatter.python = {
+        command = "sh";
+        options = [
+          "-eucx"
+          ''
+            ${lib.getExe pkgs.ruff} --fix "$@"
+            ${lib.getExe pkgs.ruff} "fmt" "$@"
+          ''
+          "--" # this argument is ignored by bash
+        ];
+        includes = [ "*.py" ];
+      };
     };
     formatter = config.treefmt.build.wrapper;
   };