fix haddock documentation links (#2542)

ghcide/src/Development/IDE/Spans/Documentation.hs

@@ -15,6 +15,7 @@ module Development.IDE.Spans.Documentation (
 import           Control.Monad
 import           Control.Monad.IO.Class
 import           Control.Monad.Extra            (findM)
+import           Data.Char
 import           Data.Either
 import           Data.Foldable
 import           Data.List.Extra
@@ -87,7 +88,7 @@ getDocumentationsTryGhc env mod names = do
             src <- toFileUriText $ lookupSrcHtmlForModule env mod
             return (doc, src)
           Nothing -> pure (Nothing, Nothing)
-      let docUri = (<> "#" <> selector <> showNameWithoutUniques name) <$> docFu
+      let docUri = (<> "#" <> selector <> makeDocAnchor (showNameWithoutUniques name)) <$> docFu
           srcUri = (<> "#" <> showNameWithoutUniques name) <$> srcFu
           selector
             | isValName name = "v:"
@@ -96,6 +97,27 @@ getDocumentationsTryGhc env mod names = do
 
     toFileUriText = (fmap . fmap) (getUri . filePathToUri)
 
+-- | Takes an arbitrary string and makes it a valid anchor ID. This is ported
+-- from the function @Haddock.Utils.makeAnchorId@ in the @haddock-api@ package,
+-- which seems to be the function in haddock that does the original encoding
+-- that we reproduce here.
+--
+-- Note that this isn't just necessary for operators, it also affects function
+-- names like @foldl'@ with apostrophes in them.
+makeDocAnchor :: T.Text -> T.Text
+makeDocAnchor = T.concatMap docEscapeChar
+  where
+    docEscapeChar :: Char -> T.Text
+    docEscapeChar c
+      | isLegal c = T.singleton c
+      | otherwise = T.pack $ '-' : show (ord c) ++ "-"
+
+    isLegal :: Char -> Bool
+    isLegal ':' = True
+    isLegal '_' = True
+    isLegal '.' = True
+    isLegal c = isAscii c && isAlphaNum c
+
 getDocumentation
  :: HasSrcSpan name
  => [ParsedModule] -- ^ All of the possible modules it could be defined in.

ghcide/test/data/hover/GotoHover.hs

@@ -1,7 +1,7 @@
 {-# LANGUAGE OverloadedStrings, TemplateHaskell #-}
 {- HLINT ignore -}
 module GotoHover ( module GotoHover) where
-import Data.Text (Text, pack)
+import Data.Text (Text, pack, foldl')
 import Foo (Bar, foo)
 
 
@@ -61,3 +61,6 @@ aa2 = $(id [| True |])
 
 hole :: Int
 hole = _
+
+externalFuncWithPrime :: Char
+externalFuncWithPrime = foldl' max 'a' "word"

ghcide/test/exe/Main.hs

@@ -3987,6 +3987,8 @@ findDefinitionAndHoverTests = let
   innL48 = Position 52  5  ;  innSig = [ExpectHoverText ["inner", "Char"], mkR 49 2 49 7]
   holeL60 = Position 62 7  ;  hleInfo = [ExpectHoverText ["_ ::"]]
   cccL17 = Position 17 16  ;  docLink = [ExpectHoverText ["[Documentation](file:///"]]
+  opL25 = Position 24 18   ;  docOpEnc = [ExpectHoverText ["[Documentation](file:///", "#v:-60--62-)"]]
+  funcL66 = Position 65 26 ;  docFuncEnc = [ExpectHoverText ["[Documentation](file:///", "#v:foldl-39-)"]]
   imported = Position 56 13 ; importedSig = getDocUri "Foo.hs" >>= \foo -> return [ExpectHoverText ["foo", "Foo", "Haddock"], mkL foo 5 0 5 3]
   reexported = Position 55 14 ; reexportedSig = getDocUri "Bar.hs" >>= \bar -> return [ExpectHoverText ["Bar", "Bar", "Haddock"], mkL bar 3 0 3 14]
   thLocL57 = Position 59 10 ; thLoc = [ExpectHoverText ["Identity"]]
@@ -4041,6 +4043,8 @@ findDefinitionAndHoverTests = let
   , test  broken broken innL48     innSig        "inner     signature              #767"
   , test  no     yes    holeL60    hleInfo       "hole without internal name       #831"
   , test  no     skip   cccL17     docLink       "Haddock html links"
+  , test  yes    skip   opL25      docOpEnc      "Haddock html doc link operator  #2542"
+  , test  yes    skip   funcL66    docFuncEnc    "Haddock html doc link function  #2542"
   , testM yes    yes    imported   importedSig   "Imported symbol"
   , testM yes    yes    reexported reexportedSig "Imported symbol (reexported)"
   , if ghcVersion == GHC90 && isWindows then