formatter with nix fmt?

[locallycompact]

I think it would be useful to simply be able to correct all of the files with nix fmt. This is the behaviour in treefmt-nix for example.

[mightyiam]

Current approach seems simple to me and I like that. What would be the benefit?

[theutz]

This is trivial to implement on a project-by-project basis, if you like @locallycompact . Here you go!

{ inputs, lib, ... }:
{
  imports = [ inputs.files.flakeModules.default ];

  perSystem =
    { pkgs, config, ... }:
    {
      treefmt.settings.formatter = {
        write-files = {
          command = "${lib.getExe pkgs.bash}";
          options = [
            "-euc"
            (lib.getExe config.files.writer.drv)
            "--"
          ];
          includes = [ "*.nix" ];
          priority = -10; # low priority means it happens before other files are linted
        };
      };
    };
}

I think this might be the better way to go about it, too, since the files derivation doesn't technically comply with the treefmt requirements for what a formatter should be.

[mightyiam]

What about the case where the file is missing?

[theutz]

Not sure exactly what you're asking, but upon rereading my response, I realized I didn't quite communicate clearly. I tend to agree with you, @mightyiam, that the current functionality is nice and simple and probably all that needs to be built-in to the module.

I was just documenting a way for @locallycompact to achieve their goal by connecting your tool to treefmt manually. I would call it a workaround if it was a bug, but it's not. 😄

[mightyiam]

The treefmt connection would be useful for files that exist. So that can be nice. But what about files that don't exist?