Create trouble shooting setup guide

[ndmitchell]

We get a lot of people who come to us with very similar setup problems. We should have a single page that says "If you have Nix + Cabal v2, be aware of ...". If your tests fail with ghcide then ... If it works in ghcide but not VS Code then perhaps....

[jacg]

Would it be possible to detect any of the typical problems automatically? For example, incompatibility of GHC version between ghcide and project.

[mpickering]

@jacg haskell-ide-engine implements this by querying ghc --version to check that it matches. This isn't really perfect though because you might not use the ghc on your path to compile a project (for example using ob build or stack build)

@ndmitchell This is the kind of stuff I was thinking of putting in documentation for hie-bios as it is usually not anything to do with ghcide. haskell/hie-bios#58

[ndmitchell]

@mpickering we really need one piece of documentation that covers everything from hie-bios to ghcide. We want to have the documentation refer to running ghcide and the output it gives you. I appreciate most of the docs will actually be about hie-bios though. Thoughts on how to square that circle?

[ndmitchell]

See https://github.com/digital-asset/ghcide/issues/135 for one of the most common issues people run into.

[jneira]

@ndmitchell do you think this is acomplished by #129#142?

[ndmitchell]

@jneira you just linked back to this ticket.

I suspect this should be a HLS thing rather than a Ghcide thing though.

[jneira]

Ops, sorry, i wanted to link your pr haskell/ghcide#142

[ndmitchell]

haskell/ghcide#142 definitely started this task, but for Ghcide it was more a brain dump of issues, rather than a curated guide. There seems a lot of information in that guide that isn't in the HLS readme. Is that because its not necessary? Is everyone having such a smooth experience that we ran out of support requests? That seems unlikely to me, but at the same time, I haven't seen many questions about failing to set up HLS, so maybe everything got better?