Raise RuntimeError if transport is None

When a client disconnects immediately after connecting, the transport
might become None. This should not lead to an assertion, since this can
happen in real-world scenarios. Use a RuntimeException instead.

Author: agners

aiohttp/web_fileresponse.py

@@ -128,7 +128,8 @@ async def _sendfile(
 
         loop = request._loop
         transport = request.transport
-        assert transport is not None
+        if transport is None:
+            raise RuntimeError("Transport is not available")
 
         try:
             await loop.sendfile(transport, fobj, offset, count)

aiohttp/web_ws.py

@@ -317,7 +317,8 @@ def _pre_start(self, request: BaseRequest) -> tuple[str | None, WebSocketWriter]
         self.force_close()
         self._compress = compress
         transport = request._protocol.transport
-        assert transport is not None
+        if transport is None:
+            raise RuntimeError("Transport is not available")
         writer = WebSocketWriter(
             request._protocol,
             transport,

tests/test_web_websocket.py

@@ -671,3 +671,12 @@ async def test_get_extra_info(
     ws._writer = ws_transport
 
     assert expected_result == ws.get_extra_info(valid_key, default_value)
+
+
+async def test_prepare_transport_not_available(make_request: _RequestMaker) -> None:
+    req = make_request("GET", "/")
+    ws = web.WebSocketResponse()
+    # Simulate transport being None
+    req._protocol.transport = None
+    with pytest.raises(RuntimeError, match="Transport is not available"):
+        await ws.prepare(req)