When checking for home unit closure, only include the actual home units in the project.

GHC gives a default "main" home unit, and it is difficult to avoid this as
each ghc session must have an active home unit at all times, but in a multiple
component session, there is no other good choice for a default unit. We could
pick one arbitrarily, but this is ugly and complicates the code a lot.

We never use this default "main" unit for anything, as the GHC sessions
corresponding to any file/component have the active unit set to the correct one
for that component.

When checking for home unit closure, we must make sure to include only the
actual units in the project, not the bogus "main" unit that GHC forces us to
have. Including the main unit seems to make the `checkHomeUnitsClosed` loop
forever for some reason.

Fixes #4046

Author: wz1000

Diff for: ghcide/session-loader/Development/IDE/Session.hs

@@ -821,12 +821,13 @@ newComponentCache recorder exts cradlePath _cfp hsc_env old_cis new_cis = do
         mkMap = Map.fromListWith unionCIs . map (\ci -> (componentUnitId ci, ci))
     let dfs = map componentDynFlags $ Map.elems cis
         uids = Map.keys cis
+        uids_set = Map.keysSet cis
     logWith recorder Info $ LogMakingNewHscEnv uids
     hscEnv' <- -- Set up a multi component session with the other units on GHC 9.4
               Compat.initUnits dfs hsc_env
 
 #if MIN_VERSION_ghc(9,3,0)
-    let closure_errs = checkHomeUnitsClosed (hsc_unit_env hscEnv') (hsc_all_home_unit_ids hscEnv') pkg_deps
+    let closure_errs = checkHomeUnitsClosed (hsc_unit_env hscEnv') uids_set pkg_deps
         pkg_deps = do
           home_unit_id <- uids
           home_unit_env <- maybeToList $ unitEnv_lookup_maybe home_unit_id $ hsc_HUG hscEnv'