WIP try dup-ing the read pipe to stderr

lib/XMonad/Internal/Shell.hs

@@ -93,26 +93,26 @@ spawnPipe
   :: (MonadReader env m, HasLogFunc env, MonadUnliftIO m)
   => T.Text
   -> m Handle
-spawnPipe = fmap fst . spawnPipeRW
+spawnPipe = liftIO . spawnPipeRW
 
-spawnPipeRW :: MonadIO m => T.Text -> m (Handle, Handle)
-spawnPipeRW x = liftIO $ do
+spawnPipeRW :: T.Text -> IO Handle
+spawnPipeRW x = do
   (rI, wI) <- createPipe
   (rO, wO) <- createPipe
   -- I'm assuming the only place this matters is when xmonad is restarted (which
   -- calls exec); since these are the ends of the pipe that xmonad will be
   -- using, this ensures they will be closed when restarting
   forM_ [wI, rO] $ \fd -> setFdOption fd CloseOnExec True
-  hI <- mkHandle wI
-  hO <- mkHandle rO
+  h <- mkHandle wI
   void $ X.xfork $ do
     void $ dupTo rI stdInput
     void $ dupTo wO stdOutput
     void $ dupTo wO stdError
     executeFile "/bin/sh" False ["-c", T.unpack x] Nothing
+  void $ dupTo stdError rO
   closeFd rI
   closeFd wO
-  return (hI, hO)
+  return h
   where
     mkHandle fd = do
       h <- fdToHandle fd