Better error messages for ide-backend / ide-backend-server mismatches

[mgsloan]

See commercialhaskell/stack-ide#33 (comment)

It'd be better to have the handshake swap things like:

• ide-backend version number
• Git hash
• Possibly things like the version of the binary package?

It'd then emit a noisy warning on mismatch. Ideally it'd also emit such info when there's a serialization error such as described in the issue above.

[urbanslug]

hmmm within wai-devel I have a small function for making errors look better. If you like it I can submit a pull request. Here is my prettyPrintErrors function: https://github.com/urbanslug/wai-devel/blob/master/src/Devel/Compile.hs#L93

It works for all SourceError https://hackage.haskell.org/package/ide-backend-0.10.0/docs/IdeSession.html#t:SourceError

[mgsloan]

This issue is about exceptions / errors in ide-backend, not about source errors.

I'd consider adding a function like `prettyPrintErrors that formatted them the same as GHC, which should be quite feasible.

[urbanslug]

Oh, sorry.