log exceptions before killing the server (haskell#1651)

* log hiedb exceptions before killing the server

* This is not the hiedb thread - fix message

* Fix handler - either an error or success

ghcide/src/Development/IDE/LSP/LanguageServer.hs

@@ -141,7 +141,12 @@ runLanguageServer options inH outH getHieDbLoc defaultConfig onConfigurationChan
             logInfo (ideLogger ide) $ T.pack $ "Registering ide configuration: " <> show initConfig
             registerIdeConfiguration (shakeExtras ide) initConfig
 
-            _ <- flip forkFinally (const exitClientMsg) $ runWithDb dbLoc $ \hiedb hieChan -> do
+            let handleServerException (Left e) = do
+                    logError (ideLogger ide) $
+                        T.pack $ "Fatal error in server thread: " <> show e
+                    exitClientMsg
+                handleServerException _ = pure ()
+            _ <- flip forkFinally handleServerException $ runWithDb dbLoc $ \hiedb hieChan -> do
               putMVar dbMVar (hiedb,hieChan)
               forever $ do
                 msg <- readChan clientMsgChan