[PR #8980/ea316336 backport][3.10] Fix resolve_host "Task was destroy…

…ed but it is pending" errors (#8967) (#8984)

**This is a backport of PR #8980 as merged into 3.11
(ea31633).**

(cherry picked from commit cd761a3)

Co-authored-by: Sam Bull <[email protected]>

CHANGES/8967.bugfix.rst

@@ -0,0 +1 @@
+Fixed resolve_host() 'Task was destroyed but is pending' errors -- by :user:`Dreamsorcerer`.

aiohttp/connector.py

@@ -824,12 +824,16 @@ def __init__(
         self._local_addr_infos = aiohappyeyeballs.addr_to_addr_infos(local_addr)
         self._happy_eyeballs_delay = happy_eyeballs_delay
         self._interleave = interleave
+        self._resolve_host_tasks: Set["asyncio.Task[List[ResolveResult]]"] = set()
 
     def close(self) -> Awaitable[None]:
         """Close all ongoing DNS calls."""
         for ev in self._throttle_dns_events.values():
             ev.cancel()
 
+        for t in self._resolve_host_tasks:
+            t.cancel()
+
         return super().close()
 
     @property
@@ -907,6 +911,8 @@ async def _resolve_host(
         resolved_host_task = asyncio.create_task(
             self._resolve_host_with_throttle(key, host, port, traces)
         )
+        self._resolve_host_tasks.add(resolved_host_task)
+        resolved_host_task.add_done_callback(self._resolve_host_tasks.discard)
         try:
             return await asyncio.shield(resolved_host_task)
         except asyncio.CancelledError:

tests/test_connector.py

@@ -9,7 +9,7 @@
 import sys
 import uuid
 from collections import deque
-from contextlib import closing
+from contextlib import closing, suppress
 from typing import Any, List, Optional, Type
 from unittest import mock
 
@@ -1667,7 +1667,41 @@ async def test_close_cancels_cleanup_handle(loop) -> None:
     assert conn._cleanup_handle is None
 
 
-async def test_close_abort_closed_transports(loop) -> None:
+async def test_close_cancels_resolve_host(loop: asyncio.AbstractEventLoop) -> None:
+    cancelled = False
+
+    async def delay_resolve_host(*args: object) -> None:
+        """Delay _resolve_host() task in order to test cancellation."""
+        nonlocal cancelled
+        try:
+            await asyncio.sleep(10)
+        except asyncio.CancelledError:
+            cancelled = True
+            raise
+
+    conn = aiohttp.TCPConnector()
+    req = ClientRequest(
+        "GET", URL("http://localhost:80"), loop=loop, response_class=mock.Mock()
+    )
+    with mock.patch.object(conn, "_resolve_host_with_throttle", delay_resolve_host):
+        t = asyncio.create_task(conn.connect(req, [], ClientTimeout()))
+        # Let it create the internal task
+        await asyncio.sleep(0)
+        # Let that task start running
+        await asyncio.sleep(0)
+
+        # We now have a task being tracked and can ensure that .close() cancels it.
+        assert len(conn._resolve_host_tasks) == 1
+        await conn.close()
+        await asyncio.sleep(0.01)
+        assert cancelled
+        assert len(conn._resolve_host_tasks) == 0
+
+        with suppress(asyncio.CancelledError):
+            await t
+
+
+async def test_close_abort_closed_transports(loop: asyncio.AbstractEventLoop) -> None:
     tr = mock.Mock()
 
     conn = aiohttp.BaseConnector(loop=loop)