Don't move invited users to new room when shutting down room (#18471)

This is confusing to users who received unwanted invites.

changelog.d/18471.misc

@@ -0,0 +1 @@
+Don't move invited users to new room when shutting down room.

synapse/handlers/room.py

@@ -1806,7 +1806,7 @@ class RoomShutdownHandler:
         ] = None,
     ) -> Optional[ShutdownRoomResponse]:
         """
-        Shuts down a room. Moves all local users and room aliases automatically
+        Shuts down a room. Moves all joined local users and room aliases automatically
         to a new room if `new_room_user_id` is set. Otherwise local users only
         leave the room without any information.
 
@@ -1949,16 +1949,17 @@ class RoomShutdownHandler:
 
                 # Join users to new room
                 if new_room_user_id:
-                    assert new_room_id is not None
-                    await self.room_member_handler.update_membership(
-                        requester=target_requester,
-                        target=target_requester.user,
-                        room_id=new_room_id,
-                        action=Membership.JOIN,
-                        content={},
-                        ratelimit=False,
-                        require_consent=False,
-                    )
+                    if membership == Membership.JOIN:
+                        assert new_room_id is not None
+                        await self.room_member_handler.update_membership(
+                            requester=target_requester,
+                            target=target_requester.user,
+                            room_id=new_room_id,
+                            action=Membership.JOIN,
+                            content={},
+                            ratelimit=False,
+                            require_consent=False,
+                        )
 
                 result["kicked_users"].append(user_id)
                 if update_result_fct:

tests/rest/admin/test_room.py

@@ -369,6 +369,47 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         self.assertEqual(200, channel.code, msg=channel.json_body)
         self._is_blocked(room_id)
 
+    def test_invited_users_not_joined_to_new_room(self) -> None:
+        """
+        Test that when a new room id is provided, users who are only invited
+        but have not joined original room are not moved to new room.
+        """
+        invitee = self.register_user("invitee", "pass")
+
+        self.helper.invite(
+            self.room_id, self.other_user, invitee, tok=self.other_user_tok
+        )
+
+        # verify that user is invited
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v3/rooms/{self.room_id}/members?membership=invite",
+            access_token=self.other_user_tok,
+        )
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(len(channel.json_body["chunk"]), 1)
+        invite = channel.json_body["chunk"][0]
+        self.assertEqual(invite["state_key"], invitee)
+
+        # shutdown room
+        channel = self.make_request(
+            "DELETE",
+            self.url,
+            {"new_room_user_id": self.admin_user},
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual(len(channel.json_body["kicked_users"]), 2)
+
+        # joined member is moved to new room but invited user is not
+        users_in_room = self.get_success(
+            self.store.get_users_in_room(channel.json_body["new_room_id"])
+        )
+        self.assertNotIn(invitee, users_in_room)
+        self.assertIn(self.other_user, users_in_room)
+        self._is_purged(self.room_id)
+        self._has_no_members(self.room_id)
+
     def test_shutdown_room_consent(self) -> None:
         """Test that we can shutdown rooms with local users who have not
         yet accepted the privacy policy. This used to fail when we tried to