Discussion: Expose Haskell-LSP-types and Haskell-LSP from the same package

In cabal 3 it is now possible for a package to have multiple public libraries. https://fgaz.me/posts/2019-11-14-cabal-multiple-libraries/

This would fix the issue where we have two packages in deadlock (Haskell-LSP-types and Haskell-LSP must be the same version) whilst also allowing us to split them out.

On the other hand it is a breaking change, requiring at least cabal 3.0 and GHC 8.8. There seems to be some caveat with cabal-install too. We should possibly look at doing this later once support for it becomes more widespread

Start by reviewing the linked Cabal multiple-libraries proposal and the current separation between Haskell-LSP-types and Haskell-LSP. Investigate the stated Cabal, GHC, and cabal-install compatibility caveats; done means deciding whether a single package can expose both libraries without unsupported toolchain requirements.

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