user_groups: Send metadata access related events on remove subgroups.

Fixes #33420.

(cherry picked from commit 6833ad8a21)

zerver/actions/user_groups.py

@@ -526,6 +526,16 @@ def remove_subgroups_from_user_group(
     *,
     acting_user: UserProfile | None,
 ) -> None:
+    if len(subgroups) == 0:
+        return
+
+    realm = user_group.realm
+    supergroups = get_recursive_supergroups_union_for_groups([user_group.id])
+    streams = list(
+        get_metadata_access_streams_via_group_ids([group.id for group in supergroups], realm)
+    )
+    old_stream_metadata_user_ids = bulk_can_access_stream_metadata_user_ids(streams)
+
     GroupGroupMembership.objects.filter(supergroup=user_group, subgroup__in=subgroups).delete()
 
     subgroup_ids = [subgroup.id for subgroup in subgroups]
@@ -555,6 +565,17 @@ def remove_subgroups_from_user_group(
 
     do_send_subgroups_update_event("remove_subgroups", user_group, subgroup_ids)
 
+    new_stream_metadata_user_ids = bulk_can_access_stream_metadata_user_ids(streams)
+    for stream in streams:
+        user_ids_losing_metadata_access = (
+            old_stream_metadata_user_ids[stream.id] - new_stream_metadata_user_ids[stream.id]
+        )
+        send_stream_deletion_event(
+            realm,
+            list(user_ids_losing_metadata_access),
+            [stream],
+        )
+
 
 @transaction.atomic(savepoint=False)
 def do_deactivate_user_group(

zerver/tests/test_events.py

@@ -2260,8 +2260,10 @@ class NormalActionsTest(BaseAction):
             check_stream_create("events[1]", events[1])
             check_subscription_peer_add("events[2]", events[2])
 
-            # Remove subgroup for next test.
+            with self.verify_action(num_events=2) as events:
-            remove_subgroups_from_user_group(user_group, [hamlet_group], acting_user=None)
+                remove_subgroups_from_user_group(user_group, [hamlet_group], acting_user=None)
+            check_user_group_remove_subgroups("events[0]", events[0])
+            check_stream_delete("events[1]", events[1])
         else:
             with self.verify_action() as events:
                 bulk_add_members_to_user_groups([user_group], [hamlet.id], acting_user=None)
@@ -2275,8 +2277,9 @@ class NormalActionsTest(BaseAction):
                 add_subgroups_to_user_group(user_group, [hamlet_group], acting_user=None)
             check_user_group_add_subgroups("events[0]", events[0])
 
-            # Remove subgroup for next test.
+            with self.verify_action() as events:
-            remove_subgroups_from_user_group(user_group, [hamlet_group], acting_user=None)
+                remove_subgroups_from_user_group(user_group, [hamlet_group], acting_user=None)
+            check_user_group_remove_subgroups("events[0]", events[0])
 
         nobody_group = NamedUserGroup.objects.get(
             name=SystemGroups.NOBODY, realm=othello.realm, is_system_group=True

zerver/tests/test_user_groups.py

@@ -572,6 +572,7 @@ class UserGroupTestCase(ZulipTestCase):
             bulk_remove_members_from_user_groups([], [hamlet.id], acting_user=None)
             bulk_remove_members_from_user_groups([test_group], [], acting_user=None)
             add_subgroups_to_user_group(test_group, [], acting_user=None)
+            remove_subgroups_from_user_group(test_group, [], acting_user=None)
 
 
 class UserGroupAPITestCase(UserGroupTestCase):