complex type variables in hover with GHC 9.2

[guibou]

Type signature in hover with GHC 9.2 are longer what they used to be.

See for example:

See the a_aI0wB. With GHC 8.10.7, it was a:

Your environment

Which OS do you use:
Linux
Which LSP client (editor/plugin) do you use:
neovim + lsp-config
Describe your project (alternative: link to the project):

Huge proprietary codebase built with bazel with a custom HLS hie setup.

Steps to reproduce

Use hover on a type. However that's not always clear, because sometimes I can observe "short" type variable. In my example, it appen on class and newtype which have type parameters.

Expected behaviour

Type variable should be short. They were used to be named as the type variable in the associated newtype or class.

Actual behaviour

Type variables are long and complex. The starts with the original name, but a noisy suffix is appended.

Include debug information

[michaelpj]

It seems likely that something changed in GHC upstream.

[hsyl20]

The following code looks incorrect:

haskell-language-server/ghcide/src/Development/IDE/GHC/Compat/Outputable.hs

Line 68 in bb73e32

renderWithContext (defaultSDocContext { sdocSuppressUniques = True }) . ppr

Because of https://gitlab.haskell.org/ghc/ghc/-/commit/8d401e50ce35525dcdc6a21fcf952c3cbf3a72d4, a name is always printed with its unique except with "user" style, but defaultSDocContext defaults to use "dump" style.

Something like this should fix it:

renderWithContext (defaultSDocContext { sdocSuppressUniques = True, sdocStyle = defaultUserStyle }) . ppr

[Kleidukos]

Well, that's a golden test that's just waiting to get written. :)

[michaelpj]

I wrote a failing test, PR incoming.

The following code looks incorrect...

Unfortunately, that's not it. I think the real issue is that we pervasively use showSDocUnsafe, re-exported from ghc, which prints uniques. I don't really know what to do about this, we have dozens of wrappers around various SDoc printing functions, it's somewhat horrifying.

[hsyl20]

Could you replace all uses of showSDocUnsafe with a call to the following showSDocForUser function which would have better defaults?

showSDocForUser :: SDoc -> String
showSDocForUser = renderWithContext $ defaultSDocContext
  { sdocStyle               = defaultUserStyle
  , sdocCanUseUnicode       = True -- I guess?
  , sdocPrintUnicodeSyntax  = True -- maybe
  , sdocSuppressUniques     = True
  }