Fix #53

Previously, if the input did not end with a newline
character and config had 'ppconf_hackAroundIncludes = True'
then due to using unlines/lines the output contained an
additional newline.

src-brittany/Main.hs

@@ -198,7 +198,7 @@ coreIO putErrorLnIO config suppressOutput inputPathM outputPathM = EitherT.runEi
       -- TODO: refactor this hack to not be mixed into parsing logic
       let hackF s = if "#include" `isPrefixOf` s then "-- BRITTANY_INCLUDE_HACK " ++ s else s
       let hackTransform =
-            if hackAroundIncludes && not exactprintOnly then List.unlines . fmap hackF . List.lines else id
+            if hackAroundIncludes && not exactprintOnly then List.intercalate "\n" . fmap hackF . lines' else id
       inputString <- liftIO $ System.IO.hGetContents System.IO.stdin
       liftIO $ parseModuleFromString ghcOptions "stdin" cppCheckFunc (hackTransform inputString)
     Just p -> liftIO $ parseModule ghcOptions p cppCheckFunc
@@ -221,7 +221,9 @@ coreIO putErrorLnIO config suppressOutput inputPathM outputPathM = EitherT.runEi
               then return $ pPrintModule config anns parsedSource
               else liftIO $ pPrintModuleAndCheck config anns parsedSource
             let hackF s = fromMaybe s $ TextL.stripPrefix (TextL.pack "-- BRITTANY_INCLUDE_HACK ") s
-            pure $ if hackAroundIncludes then (ews, TextL.unlines $ fmap hackF $ TextL.lines outRaw) else (ews, outRaw)
+            pure $ if hackAroundIncludes
+              then (ews, TextL.intercalate (TextL.pack "\n") $ fmap hackF $ TextL.splitOn (TextL.pack "\n") outRaw)
+              else (ews, outRaw)
       let customErrOrder ErrorInput{}         = 4
           customErrOrder LayoutWarning{}      = 0 :: Int
           customErrOrder ErrorOutputCheck{}   = 1

src/Language/Haskell/Brittany/Internal.hs

@@ -73,7 +73,7 @@ parsePrintModule configRaw inputText = runEitherT $ do
           then "-- BRITTANY_INCLUDE_HACK " ++ s
           else s
     let hackTransform = if hackAroundIncludes
-          then List.unlines . fmap hackF . List.lines
+          then List.intercalate "\n" . fmap hackF . lines'
           else id
     let cppCheckFunc dynFlags = if GHC.xopt GHC.Cpp dynFlags
           then case cppMode of
@@ -101,7 +101,12 @@ parsePrintModule configRaw inputText = runEitherT $ do
     let hackF s = fromMaybe s
           $ TextL.stripPrefix (TextL.pack "-- BRITTANY_INCLUDE_HACK ") s
     pure $ if hackAroundIncludes
-      then (ews, TextL.unlines $ fmap hackF $ TextL.lines outRaw)
+      then
+        ( ews
+        , TextL.intercalate (TextL.pack "\n") $ fmap hackF $ TextL.splitOn
+          (TextL.pack "\n")
+          outRaw
+        )
       else (ews, outRaw)
   let customErrOrder ErrorInput{}         = 4
       customErrOrder LayoutWarning{}      = 0 :: Int
@@ -115,6 +120,7 @@ parsePrintModule configRaw inputText = runEitherT $ do
   if hasErrors then left $ errsWarns else pure $ TextL.toStrict outputTextL
 
 
+
 -- BrittanyErrors can be non-fatal warnings, thus both are returned instead
 -- of an Either.
 -- This should be cleaned up once it is clear what kinds of errors really

src/Language/Haskell/Brittany/Internal/Utils.hs

@@ -23,6 +23,7 @@ module Language.Haskell.Brittany.Internal.Utils
   , transformDownMay
   , FirstLastView(..)
   , splitFirstLast
+  , lines'
   )
 where
 
@@ -280,3 +281,11 @@ transformDownMay :: Uniplate.Uniplate on => (on -> Maybe on) -> (on -> on)
 transformDownMay f = g where g x = maybe x (Uniplate.descend g) $ f x
 _transformDownRec :: Uniplate.Uniplate on => (on -> Maybe on) -> (on -> on)
 _transformDownRec f = g where g x = maybe (Uniplate.descend g x) g $ f x
+
+-- | similar to List.lines, but treating the case of final newline character
+-- in such a manner that this function is the inverse of @intercalate "\n"@.
+lines' :: String -> [String]
+lines' s = case break (== '\n') s of
+  (s1, []) -> [s1]
+  (s1, [_]) -> [s1, ""]
+  (s1, (_:r)) -> s1 : lines' r