test: drop pending multicast responses before TOCTOU assertion

bdraco · bdraco · commit aaf120ec23d1 · 2026-05-17T10:03:06.000-07:00
`test_service_info_async_request` patches `_is_complete` to False
to keep `async_request` looping. With `quick_timing`, the earlier
`async_get_service_info` queries leave multicast responses pending
in `out_queue` / `out_delay_queue` that snapshot the records as
they were *before* `async_update_service` swapped the registry
to `new_info`. When those stale answers flush after
`_clear_cache` they re-cache
`xxxyyy._test1-srvc-type._tcp.local. -&gt; ash-1.local. -&gt; 10.0.1.2`
and point `aiosinfo.server` at `ash-1.local.`. The patched loop
then keeps asking for an A record nobody answers, so the final
state stays on `10.0.1.2`:

    AssertionError: assert [b'\\n\\x00\\x01\\x02'] == [b'\\n\\x00\\x01\\x03']

Drop the pending entries from both queues before clearing the
cache. The already-scheduled `loop.call_at` for each queue fires
on the empty deque and is a no-op, so this is deterministic and
adds no wall-clock delay.
diff --git a/tests/test_asyncio.py b/tests/test_asyncio.py
@@ -695,6 +695,16 @@ async def test_service_info_async_request(quick_timing: None) -> None:
     assert aiosinfos[1] is not None
     assert aiosinfos[1].addresses == [socket.inet_aton("10.0.1.5")]
 
+    # Drop pending multicast responses queued under the original
+    # `info` / `info2` registrations. Their snapshots predate the
+    # `async_update_service` swap, so if they flushed after
+    # `_clear_cache` below they would poison `aiosinfo.server`
+    # with `ash-1.local.` and the `_is_complete=False` loop would
+    # then keep asking for an A record nobody answers. The pending
+    # `loop.call_at` for each queue fires harmlessly on the empty
+    # deque.
+    aiozc.zeroconf.out_queue.queue.clear()
+    aiozc.zeroconf.out_delay_queue.queue.clear()
     aiosinfo = AsyncServiceInfo(type_, registration_name)
     _clear_cache(aiozc.zeroconf)
     # Generating the race condition is almost impossible
