haskell-language-server Remove `hie-compat`

After removing support for GHC 9.4, I was in the mood of cleaning up a bit more. While removing references to GHC 9.4, I realized that some parts of HLS are referring to even older versions of GHC.

Now, some people may hate me for that, but: I completely removed the now obsolete hie-compat library.

hie-compat is a compatibility library backporting support of Haskell IDE Engine (HIE) features to older versions of GHC. Since GHC 9.2, hie-compat only re-exported definitions already present in the ghc library, and so, is essentially obsolete.

FYI: We still have hie-compat in the dependency graph, because some libraries (e.g., hiedb) are using it.

This may be a bit harsh, but let me know what you think!

Jun 04 '25 17:06 dschrempf

Yeah, I think this is a good idea. In principle, I think we'd like to have some kind of compatibility layer library, but in practice I think it's just spread out everywhere.

Jun 05 '25 07:06 michaelpj

There is Development.IDE.GHC.Compat, which we could extract into a separate package. That would probably make sense.

Jun 05 '25 08:06 dschrempf

Any other opinions? (I don't feel like dragging this along for too long, but maybe there is a way forward?)

Jun 12 '25 12:06 dschrempf

I think @wz1000 is most likely to have a real opinion?

Jun 12 '25 19:06 michaelpj

It seems there are no more opinions. I sgguest reviewing/merging or closing this PR.

Jun 23 '25 19:06 dschrempf

I think we just need an opinion from @wz1000

Jun 24 '25 09:06 michaelpj

I think we should go ahead and rebase/review/merge or close.

Jul 09 '25 13:07 dschrempf

I think this is fine, but we do lose a bit of flexibility by losing the ability to backport fixes and improvements to hie file generation. The format is more stable now, so perhaps that isn't such a big concern and we just require upgrading the ghc version to get access to newer hie file fixes.

Jul 10 '25 09:07 wz1000

Thank you @wz1000 for your opinion. I have rebased the PR.

I think it is good to remove unnecessary compability layers. The only concern I have is that on the Hackage page of hie-compat (https://hackage.haskell.org/package/hie-compat) we link to this repository, and after merging this PR the relevant files will be gone.

Jul 30 '25 13:07 dschrempf

Nothing stops us reviving the package and publishing new versions in the future if we need, so let's do this for now.

Jul 30 '25 14:07 michaelpj

I am unsure what the two failing checks mean. Let me know, if I can do something about them! @michaelpj

Jul 31 '25 05:07 dschrempf