incorrect .merlin but no warning when using per_module

[Khady]

We have a library using per_module in the preprocess part. It seems that dune generates an incorrect .merlin file as soon as per_module is used. It doesn't include the FLG -ppx ... line.

An easy way to reproduce (with dune 1.10 at least) is to create a library with a single file and this dune file:

(library
 (name demo)
 (preprocess (per_module ((pps lwt_ppx ppx_expect) demo))))

[ghost]

Yh, it's because the merlin ppx config is global to a directory. We have a plan with @trefis to change the way dune communicates the config to merlin and in particular make it per-file rather than per-directory.

[Khady]

I understand that there is a plan like this. I think it was mentioned in the issue which led to the introduction of the warning when dune can't generate a full .merlin file. Here we were surprised because there is no such warning, dune is silent about the problem.

[ghost]

Ah indeed. That seems wrong. I suppose we wanted to fix the problem where one has several library stanzas in the same directory but didn't consider this case. We should emit a warning in this case as well.

[voodoos]

@Khady this should be fixed with dune 2.8.0 : config is per-module now so it is no more approximated

[rgrinberg]

Why was this re-opened?