Building Opam Packages: Patches

[rgrinberg]

When building an opam package, we're allowed to patch any source we want by providing patch files. To support this in dune, we need a "patch" action.

[Alizter]

This will also be useful for pre/post processing in various stanzas.

[rgrinberg]

This has been implemented already. A further improvement can be to implement patch in dune and to drop the reliance on the external program.

[Alizter]

Some useful links:

• https://www.artima.com/weblogs/viewpost.jsp?thread=164293
• https://github.com/hannesm/patch

[recoules]

@Alizter @kit-ty-kate Sorry to revive this old topic, but is there any action planned to introduce "patch" action in dune ?

It would help to package "vendored" submodule by applying a patch in the build directory during the "copy" instead of having to rely on unsafe approach like this one : ocaml-bitwuzla.

[Alizter]

@recoules We have a patch action internally that is used by package management. We use this to translate build steps from opam into ones dune can understand and run. It wouldn't be too difficult to expose this in the user-facing action language for dune lang.

Currently this patch action is a wrapper around calling a patch binary. This is what opam used to do. They have since switched to using https://github.com/hannesm/patch which I mentioned earlier in this thread. I also plan to vendor and use this in dune.

Ideally I would do the re-implementation first and make sure it is working in package management and has cross-platform support + portability. This is something I was planning to tackle soon. I think it then makes sense to afterwards expose this in dune lang as a complete feature.

[recoules]

@Alizter It would be great, thank you :)
I stay tuned for future news.

[Alizter]

FTR I have a reimplementation for this ready based on https://github.com/hannesm/patch however there are some issues with our current tests where it falls short. I will need to fix the upstream code and this hasn't been a priority as of late.

[recoules]

Hi @Alizter,

I hope you are going well.
I just did a new release of the OCaml bitwuzla binding, and I am wondering where are your experiment with "builtin" patch command in the dune process ?

Regards,

PS: if you have an experimental branch for dune somewhere, I can "beta-test" it on bitwuzla if you want.

[Alizter]

Hi @recoules, I don't have anything I can push to a branch yet. The experiment I mentioned was about changing the implementation of patch in dune to use the ocaml one, but it seems you are after a user-facing patch action. This is a separate feature request from the current issue. If you think that is something you would like as a user, then I can create a new issue to track it. I don't know if I will have time to work on it soon however.

[recoules]

@Alizter It would be nice :)
It is not urgent since the current workaround is functional, but it would be cleaner and more robust if it were directly integrated in the dune workflow (the same way it is in opam).