Infix backticked holes get their backticks deleted once filled

[masaeedu]

Steps to reproduce

Write this:

data A = A

foo :: A -> A -> A
foo A A = A

test :: A -> A -> A
test a1 a2 = a1 `_` a2

Open up the context menu on the hole and select "replace with foo".

Expected behaviour

The implementation should now look like:

test :: A -> A -> A
test a1 a2 = a1 `foo` a2

Actual behaviour

The implementation now looks like:

test :: A -> A -> A
test a1 a2 = a1 foo a2

[isovector]

My guess is that this is a bug in the exactprint machinery, that it's dropping the backtick annotations.

[isovector]

But this isn't Wingman; I don't provide any replace with _ code actions.

[Ailrun]

Oh, sorry. I somehow thought this is related with Wingman.

[isovector]

No worries, I did too!

[isovector]

I think this (and all analogous pieces of code) are the offender

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

Lines 229 to 230 in 607ae3b

	(anns, val') <- annotate dflags needs_space val
	modifyAnnsT $ mappend anns

IIUC, exactprint attaches annotations to source spans, which get overwritten when we replace a node. I think if we read the annotations off the node that used to be there, and attach them to the newly replaced node, this should fix a bunch of issues --- including that big ugly needsParensSpace thing (or at least, the space part of it.)

[isovector]

(all of this assumes that replace with _ uses ExactPrint)

[isovector]

Which it doesn't seem to, but I think that will fix some problems in WIngman anyway.

[jneira]

Maybe the cause is the code is using the ParseModule version without annotations?

haskell-language-server/ghcide/src/Development/IDE/Core/Rules.hs

Lines 197 to 207 in 607ae3b

	-- | WARNING:
	-- We currently parse the module both with and without Opt_Haddock, and
	-- return the one with Haddocks if it -- succeeds. However, this may not work
	-- for hlint or any client code that might need the parsed source with all
	-- annotations, including comments.
	-- For that use case you might want to use `getParsedModuleWithCommentsRule`
	-- See https://github.com/haskell/ghcide/pull/350#discussion_r370878197
	-- and https://github.com/mpickering/ghcide/pull/22#issuecomment-625070490
	-- GHC wiki about: https://gitlab.haskell.org/ghc/ghc/-/wikis/api-annotations
	getParsedModuleRule :: Rules ()
	getParsedModuleRule =

If that is the case replacing it with:

haskell-language-server/ghcide/src/Development/IDE/Core/Rules.hs

Lines 270 to 273 in 607ae3b

	-- | This rule provides a ParsedModule preserving all annotations,
	-- including keywords, punctuation and comments.
	-- So it is suitable for use cases where you need a perfect edit.
	getParsedModuleWithCommentsRule :: Rules ()

could fix it

[berberman]

This code action is provided by ghcide, which depends on diagnostic messages, not parsed ast.

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

Lines 677 to 689 in 607ae3b

	suggestFillHole :: Diagnostic -> [(T.Text, TextEdit)]
	suggestFillHole Diagnostic{_range=_range,..}
	| Just holeName <- extractHoleName _message
	, (holeFits, refFits) <- processHoleSuggestions (T.lines _message)
	= map (proposeHoleFit holeName False) holeFits
	++ map (proposeHoleFit holeName True) refFits
	| otherwise = []
	where
	extractHoleName = fmap head . flip matchRegexUnifySpaces "Found hole: ([^ ]*)"
	proposeHoleFit holeName parenthise name =
	( "replace " <> holeName <> " with " <> name
	, TextEdit _range $ if parenthise then parens name else name)
	parens x = "(" <> x <> ")"

[jneira]

So updating the regexp should fix it, it seems it could be a good first issue