[PR #9803/fc912352 backport][3.11] Small performance improvement to drain (#9807)

Co-authored-by: J. Nick Koston <[email protected]>

Author: patchback[bot]

aiohttp/base_protocol.py

@@ -89,7 +89,7 @@ def connection_lost(self, exc: Optional[BaseException]) -> None:
             )
 
     async def _drain_helper(self) -> None:
-        if not self.connected:
+        if self.transport is None:
             raise ClientConnectionResetError("Connection lost")
         if not self._paused:
             return

aiohttp/http_writer.py

@@ -172,8 +172,9 @@ async def drain(self) -> None:
           await w.write(data)
           await w.drain()
         """
-        if self._protocol.transport is not None:
-            await self._protocol._drain_helper()
+        protocol = self._protocol
+        if protocol.transport is not None and protocol._paused:
+            await protocol._drain_helper()
 
 
 def _safe_header(string: str) -> str:

tests/test_benchmarks_client_request.py

@@ -88,6 +88,7 @@ class MockProtocol(asyncio.BaseProtocol):
 
         def __init__(self) -> None:
             self.transport = MockTransport()
+            self._paused = False
 
         @property
         def writing_paused(self) -> bool: