Fix regression with connection upgrade

CHANGES/7879.bugfix

@@ -0,0 +1 @@
+Fixed a regression where connection may get closed during upgrade. -- by :user:`Dreamsorcerer`

aiohttp/client_reqrep.py

@@ -940,19 +940,15 @@ def _response_eof(self) -> None:
         if self._closed:
             return
 
-        if self._connection is not None:
-            # websocket, protocol could be None because
-            # connection could be detached
-            if (
-                self._connection.protocol is not None
-                and self._connection.protocol.upgraded
-            ):
-                return
-
-            self._release_connection()
+        # protocol could be None because connection could be detached
+        protocol = self._connection and self._connection.protocol
+        # Mypy bug: https://github.com/python/mypy/issues/16565
+        if protocol is not None and protocol.upgraded:  # type: ignore[union-attr]
+            return
 
         self._closed = True
         self._cleanup_writer()
+        self._release_connection()
 
     @property
     def closed(self) -> bool:
@@ -1048,7 +1044,10 @@ async def read(self) -> bytes:
         elif self._released:  # Response explicitly released
             raise ClientConnectionError("Connection closed")
 
-        await self._wait_released()  # Underlying connection released
+        protocol = self._connection and self._connection.protocol
+        # Mypy bug: https://github.com/python/mypy/issues/16565
+        if protocol is None or not protocol.upgraded:  # type: ignore[union-attr]
+            await self._wait_released()  # Underlying connection released
         return self._body
 
     def get_encoding(self) -> str:

tests/test_client_functional.py

@@ -174,6 +174,25 @@ async def handler(request):
     assert 1 == len(client._session.connector._conns)
 
 
+async def test_upgrade_connection_not_released_after_read(aiohttp_client: Any) -> None:
+    async def handler(request: web.Request) -> web.Response:
+        body = await request.read()
+        assert b"" == body
+        return web.Response(
+            status=101, headers={"Connection": "Upgrade", "Upgrade": "tcp"}
+        )
+
+    app = web.Application()
+    app.router.add_route("GET", "/", handler)
+
+    client = await aiohttp_client(app)
+
+    resp = await client.get("/")
+    await resp.read()
+    assert resp.connection is not None
+    assert not resp.closed
+
+
 async def test_keepalive_server_force_close_connection(aiohttp_client: Any) -> None:
     async def handler(request):
         body = await request.read()