fix disappearing comments

Author: GuillaumedeVolpiano

lib/Language/Haskell/Stylish/Step/Data.hs

@@ -93,19 +93,28 @@ step cfg = makeStep "Data" \ls m -> Editor.apply (changes m) ls
     changes :: Module -> Editor.Edits
     changes = foldMap (formatDataDecl cfg) . dataDecls
 
-    getComments :: GHC.AddEpAnn -> [GHC.LEpaComment]
-    getComments (GHC.AddEpAnn _ epaLoc) = case epaLoc of
-        GHC.EpaDelta _ comments -> comments
-        GHC.EpaSpan _ -> []
+    getComments :: GHC.SrcSpanAnnA -> [GHC.LEpaComment]
+    getComments (GHC.EpAnn _ _ c)= GHC.priorComments c
+
+    -- ugly workaround to make sure we don't reprint a haddock
+    -- comment before a data declaration after a data
+    -- declaration…
+    filterLoc :: GHC.RealSrcSpan -> [GHC.LEpaComment] -> [GHC.LEpaComment]
+    filterLoc loc = filter afterStart
+      where
+        afterStart c = comLoc c >= GHC.srcSpanStartLine loc
+        comLoc (GHC.L l _) = case l of
+                               GHC.EpaSpan (GHC.RealSrcSpan l' _)      -> GHC.srcSpanStartLine l'
+                               _                                       -> undefined -- hopefully we don't get an EpaDelta or an UnhelpfulSpan passed to us
 
     dataDecls :: Module -> [DataDecl]
     dataDecls m = do
         ldecl <- GHC.hsmodDecls $ GHC.unLoc m
-        GHC.TyClD _ tycld <- pure $ GHC.unLoc ldecl
+        (GHC.TyClD _ tycld, annos) <- pure $ (\(GHC.L anno ty) -> (ty, anno)) ldecl
         loc <- maybeToList $ GHC.srcSpanToRealSrcSpan $ GHC.getLocA ldecl
         case tycld of
             GHC.DataDecl {..} -> pure $ MkDataDecl
-                { dataComments = foldMap getComments tcdDExt
+                { dataComments = filterLoc loc . getComments $ annos
                 , dataLoc      = loc
                 , dataDeclName = tcdLName
                 , dataTypeVars = tcdTyVars
@@ -180,8 +189,8 @@ putDataDecl cfg@Config {..} decl = do
             | not . null $ GHC.dd_cons defn -> do
                 forM_ (flagEnds constructorComments) $ \(CommentGroup {..}, firstGroup, lastGroup) -> do
                     forM_ cgPrior $ \lc -> do
-                        putComment $ GHC.unLoc lc
-                        consIndent lineLengthAfterEq
+                      putComment . GHC.unLoc $ lc
+                      consIndent lineLengthAfterEq
 
                     forM_ (flagEnds cgItems) $ \((lcon, mbInlineComment), firstItem, lastItem) -> do
                         unless (isGADT decl) $ do