Export action on type family exports with constructors (Tyfam(..))

[googleson78]

Your environment

HLS version:
1.5.1
Which OS do you use:
Debian
Which LSP client (editor/plugin) do you use:
LanguageClient-neovim

resolver: nightly-2021-09-12

Steps to reproduce

Add a file with a type family, with an empty export list. Use the "export definition" action on the type family. HLS generates an export with exported constructors, even though type families don't have constructors.

Expected behaviour

An export without constructors.

Actual behaviour

An export with constructors, which don't exist, causing an additional warning.

[drsooch]

haskell-language-server/ghcide/src/Development/IDE/Plugin/CodeAction.hs

Lines 602 to 617 in f62ec3e

	printExport :: ExportsAs -> T.Text -> T.Text
	printExport ExportName x = parenthesizeIfNeeds False x
	printExport ExportPattern x = "pattern " <> x
	printExport ExportAll x = parenthesizeIfNeeds True x <> "(..)"
	isTopLevel :: Range -> Bool
	isTopLevel l = (_character . _start) l == 0
	exportsAs :: HsDecl GhcPs -> Maybe (ExportsAs, Located (IdP GhcPs))
	exportsAs (ValD _ FunBind {fun_id}) = Just (ExportName, reLoc fun_id)
	exportsAs (ValD _ (PatSynBind _ PSB {psb_id})) = Just (ExportPattern, reLoc psb_id)
	exportsAs (TyClD _ SynDecl{tcdLName}) = Just (ExportName, reLoc tcdLName)
	exportsAs (TyClD _ DataDecl{tcdLName}) = Just (ExportAll, reLoc tcdLName)
	exportsAs (TyClD _ ClassDecl{tcdLName}) = Just (ExportAll, reLoc tcdLName)
	exportsAs (TyClD _ FamDecl{tcdFam}) = Just (ExportAll, reLoc $ fdLName tcdFam)
	exportsAs _ = Nothing

Looks like type families default to having (..). Even the test in ghcide/test/exe/Main.hs expects there to be (..).

[drsooch]

That being said I tested quickly myself and I was able to export a TypeFamily with (..) with ghc generated no errors on compile. This was on 8.10.7 not sure if it's something new.

[googleson78]

It triggers a warning, I believe this one - https://downloads.haskell.org/ghc/latest/docs/html/users_guide/using-warnings.html#ghc-flag--Wdodgy-exports