feature wish: propose to auto-require packages when doing C-c C-s?

[erikmd]

currently, when working with an OCaml project involving a large number of dependencies, it is difficult to perform tests in a REPL (C-c C-s) with the proper packages loaded.

Granted, one can manually evaluate #load "topfind";; then #require "jwto";; or so for each package, but it quickly becomes cumbersome on realistic projects.

Would it be possible to implement an elisp feature that would pre-compute the list of packages (e.g. from the PKG lines involved in a .merlin file) and propose to run a command like this when doing C-c C-s?

OCaml REPL to run: OCAMLFIND_COMMANDS='ocamlc=ocaml' ocamlfind ocamlc -linkpkg -package jwto 

Note: this can be tested in a terminal by running:

$ opam install jwto
$ packages="jwto"
$ OCAMLFIND_COMMANDS='ocamlc=ocaml' ocamlfind ocamlc -linkpkg $(for arg in $packages; do echo "-package $arg"; done)

        OCaml version 4.05.0

#show Jwto;;

What do you think?
Maybe this idea should be further refined, but AFAICT one such feature would be really great!

Cc @Chris00 @monnier @cpitclaudel @Aleridia FYI

[Chris00]

Discussion: https://discuss.ocaml.org/t/tuareg-ocaml-repl-request-for-feedback-about-a-proper-way-to-auto-require-packages/8329

[monnier]

As mentioned in the discussion to which Chris linked, Dune currently works better if you structure your project into a (set of) libraries together with an almost empty top-level executable. So I think it would make sense to start by supporting only the case where the Dune project is a library rather than an executable.

[Chris00]

Yes, dune top should make it not too difficult.