Formatting dune files on save while the build is running

[mbarbin]

Desired Behavior

Imagine you have an editor extension enabled that can format your dune files (dune, dune-project, etc.) on save, using dune format-dune-file under the hood. I think now if you have a build running in watch mode in the project, this no longer works. The format command conflicts with the build locks.

I think this use to work before dune.3.21 but I suspect something changed.

Repro?

I'd appreciate if someone else can confirm as I am not sure exactly sure from where this workflow comes from (dune.el?). I have noticed it via some other layer with the reformatter emacs package (using this setup). Not sure if this applies to other users. Thanks!

[Alizter]

This is spinning up its own scheduler every time rather than connecting to an existing build server like we have for other commands. This can be fixed by doing the same thing we do for build.ml, exec.ml and runtest.ml which is to send an equivalent RPC request instead. That should be simple enough since we already have such a request, however I am uncertain if it shares the same implementation as dune format-dune-file that will need to be checked.