gbuild and buildOrReplLib contain large amount of duplication

[mpickering]

In Distribution.Simple.GHC the buildOrReplLib and gbuild are essentially duplicates of each other. The fact they are not identical leads to bugs such as #8639.

I will combine together the implementations.

[philderbeast]

I will combine together the implementations.

Are you self-assigning this @mpickering? I'd be happy to help as I like these kinds of clean up tasks.

[arjunkathuria]

Hi !

I'm looking to make my first! contribution to Cabal after being encouraged by @angerman

Since this issue has a pr-welcome tag, wondering if help is still required with this.
If it's covered, I'd be happy to take another one off of your hands.

[mpickering]

In some ways this task is simple, but great care should be taken to get this right as this code is executed on essentially every invocation of cabal-install. I would suggest for a first issue it's quite high-risk.

[arjunkathuria]

Noted, Matthew.

i'll try working on something that's a better fit for now.
#9298 seems promising.

feel free to tag me on other relevant issues. Happy to help where i can : )

[alt-romes]

@philderbeast I accidentally looked a bit into this duplication today because I thought it would be a good refactor when I was working on #7339, not knowing about this ticket's existence.

I took a look at what needed to be done and wrote down some comments, which might be useful in your tackling this ticket. The commit with these notes is ded79d4.

In the meantime I'm going back to #7339. Good luck and thanks!

[philderbeast]

@mpickering and @alt-romes, the duplication is a bit more widespread. Within Cabal/src/Distribution/Simple/GHC.hs there is duplication between buildOrReplLib and gbuild as mentioned but there are also the same named functions in Cabal/src/Distribution/Simple/GHCJS.hs.

@luite and @hsyl20 do you think we could or should deduplicate buildOrReplLib and gbuild there too?

[hsyl20]

@luite and @hsyl20 do you think we could or should deduplicate buildOrReplLib and gbuild there too?

No strong opinion but GHCJS is unmaintained and people should be encouraged to switch to GHC's JS backend. Hence Cabal support for GHCJS might be dropped at some point and this code removed, so there isn't really a need to improve it.