fix(agent_execution): resolve ActiveTask 'destroyed but pending' warning during teardown (a2aproject#1122)

Fixes a2aproject#1121. This PR resolves the issue where `ActiveTask` would throw
an asyncio warning when being garbage collected, by ensuring the
`_producer_task` is properly awaited during the `_run_consumer` teardown
path, allowing queues to properly close without leaving dangling pending
background tasks.

---------

Co-authored-by: mykytanetipa <mykytanetipa@google.com>

Author: arunmm8335

src/a2a/server/agent_execution/active_task.py

@@ -587,6 +587,19 @@ async def _run_consumer(self) -> None:
             self._is_finished.set()
             self._request_queue.shutdown(immediate=True)
             await self._event_queue_agent.close(immediate=True)
+
+            if self._producer_task and not self._producer_task.done():
+                try:
+                    await self._producer_task
+                except asyncio.CancelledError:
+                    pass
+                except Exception as e:  # noqa: BLE001
+                    logger.debug(
+                        'Consumer[%s]: Awaited producer_task raised %r',
+                        self._task_id,
+                        e,
+                    )
+
             async with self._lock:
                 self._reference_count -= 1
             logger.debug('Consumer[%s]: Finishing', self._task_id)

tests/server/agent_execution/test_active_task.py

@@ -895,3 +895,87 @@ async def execute_mock(req, q):
     assert len(events) == 0
 
     await active_task.cancel(request_context)
+
+
+@pytest.mark.timeout(5)
+@pytest.mark.asyncio
+async def test_producer_awaited_on_normal_completion():
+    """Verify producer is awaited before cleanup to prevent GC warnings.
+
+    Regression test for #1121: when the consumer finishes first (normal
+    completion path), the producer must be awaited before
+    _maybe_cleanup() releases the ActiveTask reference, otherwise asyncio
+    logs "Task was destroyed but it is pending!".
+    """
+    agent_executor = Mock()
+    task_manager = Mock()
+    cleanup_called = False
+
+    def on_cleanup(_task: ActiveTask) -> None:
+        nonlocal cleanup_called
+        cleanup_called = True
+
+    active_task = ActiveTask(
+        agent_executor=agent_executor,
+        task_id='test-task-id',
+        task_manager=task_manager,
+        on_cleanup=on_cleanup,
+    )
+
+    execute_started = asyncio.Event()
+    execute_barrier = asyncio.Event()
+
+    async def execute_mock(req, q):
+        execute_started.set()
+        await execute_barrier.wait()
+
+    agent_executor.execute = AsyncMock(side_effect=execute_mock)
+    agent_executor.cancel = AsyncMock()
+    task_manager.get_task = AsyncMock(
+        return_value=Task(
+            id='test-task-id',
+            status=TaskStatus(state=TaskState.TASK_STATE_WORKING),
+        )
+    )
+    task_manager.save_task_event = AsyncMock()
+    task_manager.ensure_task_id = AsyncMock(
+        return_value=Task(
+            id='test-task-id',
+            status=TaskStatus(state=TaskState.TASK_STATE_WORKING),
+        )
+    )
+    task_manager.process = AsyncMock(side_effect=lambda x: x)
+
+    request_context = Mock(spec=RequestContext)
+    request_context.call_context = ServerCallContext()
+    request_context.context_id = 'test-context'
+    request_context.message = None
+
+    await active_task.enqueue_request(request_context)
+    await active_task.start(
+        call_context=ServerCallContext(), create_task_if_missing=True
+    )
+
+    await execute_started.wait()
+
+    if active_task._consumer_task:
+        active_task._consumer_task.cancel()
+
+        # Release the producer so it can finish its work and loop back
+        # to get(), where it will receive QueueShutDown.
+        execute_barrier.set()
+
+        try:
+            await active_task._consumer_task
+        except asyncio.CancelledError:
+            pass
+
+    await active_task._is_finished.wait()
+
+    assert active_task._producer_task is not None
+    assert active_task._producer_task.done(), (
+        'Producer task should be done after consumer teardown'
+    )
+    assert cleanup_called, (
+        'on_cleanup should be called after producer is drained'
+    )