Support public sublibraries

[expipiplus1]

It would be super to be able to use cabal 3's visibility: public feature (https://fgaz.me/posts/2019-11-14-cabal-multiple-libraries/) on auxiliary libraries. Personally I'd like to make use of this feature to avoid cluttering the write-only namespace on Hackage/Stackage. This is also quite important IMO for backpack due to the number of different libraries required for a backpackized project.

Related: #4910, #2540 and #4564

I couldn't find an existing issue for this, and perhaps this is a better fit for the Stackage repo.

[expipiplus1]

oh, perhaps stack already has support here, I see there's a test here: https://github.com/commercialhaskell/stack/tree/master/test/integration/tests/cabal-public-sublibraries

[Qiu233]

Is there a way to declare multiple libraries in package.yaml?

[mpilgrem]

@Qiu233, Cabal sublibraries? I think not, given: sol/hpack#483.

[hasufell]

@mpilgrem hpack is an optional feature. One doesn't need to use it in order to use stack.

[mpilgrem]

On the topic of Stack supporting Cabal's public sublibraries, there is also #4745 (component-based builds).

[mmhat]

oh, perhaps stack already has support here, I see there's a test here: https://github.com/commercialhaskell/stack/tree/master/test/integration/tests/cabal-public-sublibraries

I think this issue can be closed, can't it?

[mpilgrem]

@mmhat, if you are proposing this issue be closed because Stack supports public sublibraries, Stack does not (yet) support them.

[mpilgrem]

I am closing this issue because #6343 has been merged.