error messages are stored after NG, not printed in stderr.

Language/Haskell/GhcMod/Utils.hs

@@ -1,14 +1,13 @@
 module Language.Haskell.GhcMod.Utils where
 
 
-import MonadUtils (MonadIO, liftIO)
 import Control.Exception
 import Control.Monad.Error (MonadError(..), Error(..))
+import MonadUtils (MonadIO, liftIO)
 import System.Directory (getCurrentDirectory, setCurrentDirectory)
-import System.Process (readProcessWithExitCode)
 import System.Exit (ExitCode(..))
-import System.IO (hPutStrLn, stderr)
 import System.IO.Error (tryIOError)
+import System.Process (readProcessWithExitCode)
 
 -- dropWhileEnd is not provided prior to base 4.5.0.0.
 dropWhileEnd :: (a -> Bool) -> [a] -> [a]
@@ -34,9 +33,9 @@ readProcess' cmd opts = do
   (rv,output,err) <- liftIO $ readProcessWithExitCode cmd opts ""
   case rv of
     ExitFailure val -> do
-        liftIO $ hPutStrLn stderr err
         throwError $ strMsg $
           cmd ++ " " ++ unwords opts ++ " (exit " ++ show val ++ ")"
+              ++ "\n" ++ err
     ExitSuccess ->
         return output
 

elisp/ghc-check.el

@@ -110,7 +110,7 @@ nil            does not display errors/warnings.
 	      (setq mode-line-process (format " %d:%d" elen wlen)))))
 	(force-mode-line-update))))
    (t
-    (let* ((err (buffer-substring-no-properties (point-min) (point)))
+    (let* ((err (ghc-unescape-string (buffer-substring-no-properties (+ (point) 3) (point-max))))
 	   (info (ghc-make-hilit-info
 		  :file "Fail errors:"
 		  :line 0

elisp/ghc-func.el

@@ -32,6 +32,17 @@
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+(defun ghc-unescape-string (str)
+  (with-temp-buffer
+    (insert str)
+    (goto-char (point-min))
+    (while (search-forward "\\n" nil t) (replace-match "\n" nil t))
+    (goto-char (point-min))
+    (while (search-forward "\\\\" nil t) (replace-match "\\" nil t))
+    (buffer-substring-no-properties (point-min) (point-max))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
 (defmacro ghc-add (sym val)
   `(setq ,sym (cons ,val ,sym)))