Exit with non-zero exitcode if wrapper fails to launch (#4110)

* Exit with non-zero exitcode if wrapper fails to launch

Only when in LSP mode, we want to launch the LSP server that offers the
restart capability.

* Install recommended GHC version for release wrapper tests

---------

Co-authored-by: Michael Peyton Jones <me@michaelpj.com>

.github/scripts/test.sh

@@ -48,6 +48,8 @@ test_all_hls() {
             fi
         fi
     done
+    # install the recommended GHC version so the wrapper can launch HLS
+    ghcup install ghc --set recommended
     "$bindir/haskell-language-server-wrapper${ext}" typecheck "${test_module}" || fail "failed to typecheck with HLS wrapper"
 }
 

exe/Wrapper.hs

@@ -99,8 +99,10 @@ main = do
             Left err -> do
               T.hPutStrLn stderr (prettyError err NoShorten)
               case args of
-                Ghcide _ -> launchErrorLSP recorder (prettyError err Shorten)
-                _        -> pure ()
+                Ghcide (GhcideArguments { argsCommand = Main.LSP }) ->
+                    launchErrorLSP recorder (prettyError err Shorten)
+
+                _ -> exitFailure
 
 launchHaskellLanguageServer :: Recorder (WithPriority (Doc ())) -> Arguments -> IO (Either WrapperSetupError ())
 launchHaskellLanguageServer recorder parsedArgs = do