Fix the false positive about AST differences

Comments that have more than one consecutive blank line will be rendered
with just a single blank line due to how our rendering engine works. I think
that the engine work correctly in this case and we want to generally
normalize blank lines. So what should be fixed is just the check. For that
we remove extra consecutive blank lines when we construct ‘Comment’ values.

data/examples/other/multiple-blank-line-comment-out.hs

@@ -0,0 +1,9 @@
+module A where
+
+a =
+  b
+    [ f
+    {-,
+
+                                       -}
+    ]

data/examples/other/multiple-blank-line-comment.hs

@@ -0,0 +1,10 @@
+module A where
+
+a =
+  b
+    [ f
+ {-,
+
+
+                                    -}
+    ]

src/Ormolu/Parser/CommentStream.hs

@@ -103,7 +103,7 @@ mkComment ::
 mkComment ls (L l s) = (ls', comment)
   where
     comment =
-      L l . Comment atomsBefore . fmap dropTrailing $
+      L l . Comment atomsBefore . removeConseqBlanks . fmap dropTrailing $
         if "{-" `L.isPrefixOf` s
           then case NE.nonEmpty (lines s) of
             Nothing -> s :| []
@@ -143,26 +143,6 @@ isMultilineComment (Comment _ (x :| _)) = "{-" `L.isPrefixOf` x
 ----------------------------------------------------------------------------
 -- Helpers
 
--- | Get a 'String' from 'GHC.AnnotationComment'.
-unAnnotationComment :: GHC.AnnotationComment -> Maybe String
-unAnnotationComment = \case
-  GHC.AnnDocCommentNext _ -> Nothing -- @-- |@
-  GHC.AnnDocCommentPrev _ -> Nothing -- @-- ^@
-  GHC.AnnDocCommentNamed _ -> Nothing -- @-- $@
-  GHC.AnnDocSection _ _ -> Nothing -- @-- *@
-  GHC.AnnDocOptions s -> Just s
-  GHC.AnnLineComment s -> Just s
-  GHC.AnnBlockComment s -> Just s
-
-liftMaybe :: Located (Maybe a) -> Maybe (Located a)
-liftMaybe = \case
-  L _ Nothing -> Nothing
-  L l (Just a) -> Just (L l a)
-
-toRealSpan :: Located a -> Maybe (RealLocated a)
-toRealSpan (L (RealSrcSpan l) a) = Just (L l a)
-toRealSpan _ = Nothing
-
 -- | Detect and extract stack header if it is present.
 extractStackHeader ::
   [RealLocated String] ->
@@ -196,3 +176,34 @@ extractPragmas input = go initialLs id id
           Just pragma ->
             let combined = (csSoFar [], pragma)
              in go ls id (pragmasSoFar . (combined :)) xs
+
+-- | Get a 'String' from 'GHC.AnnotationComment'.
+unAnnotationComment :: GHC.AnnotationComment -> Maybe String
+unAnnotationComment = \case
+  GHC.AnnDocCommentNext _ -> Nothing -- @-- |@
+  GHC.AnnDocCommentPrev _ -> Nothing -- @-- ^@
+  GHC.AnnDocCommentNamed _ -> Nothing -- @-- $@
+  GHC.AnnDocSection _ _ -> Nothing -- @-- *@
+  GHC.AnnDocOptions s -> Just s
+  GHC.AnnLineComment s -> Just s
+  GHC.AnnBlockComment s -> Just s
+
+liftMaybe :: Located (Maybe a) -> Maybe (Located a)
+liftMaybe = \case
+  L _ Nothing -> Nothing
+  L l (Just a) -> Just (L l a)
+
+toRealSpan :: Located a -> Maybe (RealLocated a)
+toRealSpan (L (RealSrcSpan l) a) = Just (L l a)
+toRealSpan _ = Nothing
+
+-- | Remove consecutive blank lines.
+removeConseqBlanks :: NonEmpty String -> NonEmpty String
+removeConseqBlanks (x :| xs) = x :| go (null x) id xs
+  where
+    go seenBlank acc = \case
+      [] -> acc []
+      (y : ys) ->
+        if seenBlank && null y
+          then go True acc ys
+          else go (null y) (acc . (y :)) ys