Line/region indentation feature (emacs integration)

[gpetiot]

the workflow is:

• dune build @install && dune install
• add (require 'ocamlformat) to your .emacs

Disclaimer: so far what it does is applying the indentation of the (virtually) formatted output to the unformatted input, so if you break a line like this you can observe cases like:

let foo =
foooo
|> bar

because once formatted it is formatted on a single line (indented to 0)

[Julow]

This would be a nice feature ! But the fact that you have to give it line numbers in the formatted output makes it unusable, I think.
How hard it is to fix that ?

[emillon]

I agree that we'll need something like this, but it's not super clear to me how much needs to be done in ocamlformat and how much will be done by the editor.

Editor integration will be fairly large amount of work, and I think we need to step back a bit from the code and work out a spec first, and see what kind of features we'll need based on that. Then we'll be able to iterate on both. We don't want to ship a new option that will end up not being useful.

[gpetiot]

For reference there is a PR on opam-user-setup to add ocamlformat: ocaml-opam/opam-user-setup#48 I'm not familiar with the way it works but I'm not sure there is an easy way to switch from ocp-indent to ocamlformat in this tool. I'm still digging but if someone has experience with this feel free to help :)

[gpetiot]

I've reused some code from #1188 to reduce the time overhead of this feature, but there is still too much overhead compared to the current reindent feature in emacs.

[gpetiot]

Replaced by #1609