perf: await pending frames without idle worker

recognization/code/test_live.py

@@ -11,6 +11,7 @@ newest frame.
 from __future__ import annotations
 
 import os
+import asyncio
 import sys
 import threading
 import time
@@ -391,6 +392,39 @@ class ClassificationBudgetTests(unittest.TestCase):
         session.close()
         self.assertTrue(session.closed)
         self.assertIsNone(session.take_pending(timeout=0.05))
+
+    def test_async_take_keeps_latest_and_wakes_on_close(self):
+        """The server waiter must not miss a frame that beat registration, and close must wake it."""
+        session, engine, _, _ = make_session()
+
+        async def scenario():
+            session.submit_frame(1, frame_bytes())
+            session.submit_frame(2, frame_bytes())
+            first = await asyncio.wait_for(session.take_pending_async(), timeout=1.0)
+            self.assertEqual(first[0], 2)
+
+            waiting = asyncio.create_task(session.take_pending_async())
+            await asyncio.sleep(0)
+            self.assertFalse(waiting.done(), "an empty queue must not complete the waiter")
+            session.reset()
+            session.submit_frame(3, frame_bytes())
+            self.assertEqual((await asyncio.wait_for(waiting, timeout=1.0))[0], 3)
+
+            cancelled = asyncio.create_task(session.take_pending_async())
+            await asyncio.sleep(0)
+            cancelled.cancel()
+            with self.assertRaises(asyncio.CancelledError):
+                await cancelled
+            session.submit_frame(4, frame_bytes())
+            self.assertEqual((await asyncio.wait_for(session.take_pending_async(), timeout=1.0))[0], 4)
+
+            closing = asyncio.create_task(session.take_pending_async())
+            await asyncio.sleep(0)
+            session.close()
+            self.assertIsNone(await asyncio.wait_for(closing, timeout=1.0))
+            self.assertFalse(session.submit_frame(5, frame_bytes()))
+
+        asyncio.run(scenario())
         engine.shutdown()