mention: Handle mentioning deactivated user groups.

If someone tries to mention a deactivated user group,
then it is automatically converted to a silent mention
like we do for deactivated users.

zerver/lib/markdown/__init__.py

@@ -1957,6 +1957,9 @@ class UserGroupMentionPattern(CompiledInlineProcessor):
         if db_data is not None:
             user_group = db_data.mention_data.get_user_group(name)
             if user_group:
+                if user_group.deactivated:
+                    silent = True
+
                 if not silent:
                     self.zmd.zulip_rendering_result.mentions_user_group_ids.add(user_group.id)
                 name = user_group.name

zerver/tests/test_markdown.py

@@ -19,7 +19,7 @@ from zerver.actions.alert_words import do_add_alert_words
 from zerver.actions.create_realm import do_create_realm
 from zerver.actions.realm_emoji import do_remove_realm_emoji
 from zerver.actions.realm_settings import do_set_realm_property
-from zerver.actions.user_groups import check_add_user_group
+from zerver.actions.user_groups import check_add_user_group, do_deactivate_user_group
 from zerver.actions.user_settings import do_change_user_setting
 from zerver.actions.users import change_user_is_active
 from zerver.lib.alert_words import get_alert_word_automaton
@@ -2898,6 +2898,27 @@ class MarkdownMentionTest(ZulipTestCase):
 
         self.assertEqual(rendering_result.mentions_user_group_ids, set())
 
+    def test_deactivated_user_group_mention(self) -> None:
+        sender_user_profile = self.example_user("othello")
+        msg = Message(
+            sender=sender_user_profile,
+            sending_client=get_client("test"),
+            realm=sender_user_profile.realm,
+        )
+        support = self.create_user_group_for_test("support")
+        do_deactivate_user_group(support, acting_user=None)
+
+        content = "We'll add you to @*support* user group."
+        rendering_result = render_message_markdown(msg, content)
+        self.assertEqual(
+            rendering_result.rendered_content,
+            "<p>We'll add you to "
+            f'<span class="user-group-mention silent" data-user-group-id="{support.id}">support</span>'
+            " user group.</p>",
+        )
+
+        self.assertEqual(rendering_result.mentions_user_group_ids, set())
+
     def test_user_group_mention_in_quotes(self) -> None:
         user_profile = self.example_user("othello")
         message = Message(