Merge pull request #304 from numtide/readme-supported-versions

readme supported versions

README.md

@@ -387,6 +387,13 @@ That mostly means, for the given formatter:
 - You get precedence if any decisions need to be made.
 - Getting pinged if any issue is being found.
 
+## Supported Nix versions
+
+treefmt-nix works with all known Nix version.
+
+If you rely on flakes and `nix fmt`, we recommend running Nix 2.25 or Lix 2.92
+or later. See https://github.com/NixOS/nix/pull/11438
+
 ## Commercial support
 
 Looking for help or customization?

programs/nixfmt.nix

@@ -1,4 +1,12 @@
-{ mkFormatterModule, ... }:
+{
+  lib,
+  config,
+  mkFormatterModule,
+  ...
+}:
+let
+  cfg = config.programs.nixfmt;
+in
 {
   meta.maintainers = [ ];
 
@@ -9,4 +17,33 @@
       includes = [ "*.nix" ];
     })
   ];
+
+  options.programs.nixfmt = {
+    strict = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      description = ''
+        Enable a stricter formatting mode that isn't influenced
+        as much by how the input is formatted.
+      '';
+    };
+
+    width = lib.mkOption {
+      type = lib.types.nullOr lib.types.int;
+      default = null;
+      example = 120;
+      description = ''
+        Maximum width in characters [default: 100]
+      '';
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    settings.formatter.nixfmt.options =
+      lib.optionals (!isNull cfg.width) [
+        "--width"
+        (toString cfg.width)
+      ]
+      ++ lib.optional cfg.strict "--strict";
+  };
 }