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Raise RuntimeError if transport is None #11761

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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.
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@agners
agners committed Nov 13, 2025
commit 9f20389bb652daca3925e0e67cf42e3708e1680d
3 changes: 2 additions & 1 deletion aiohttp/web_fileresponse.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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")
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@webknjaz webknjaz Nov 21, 2025

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I'm not sure if this should be a RuntimeError. It's probably a ConnectionError or its subclass.

We should also ensure that it doesn't leak to the end-users and gets converted to some kind of a ClientError if they use high-level interfaces.
In fact, we already have things like ClientConnectionResetError in the hierarchy: https://docs.aiohttp.org/en/stable/client_reference.html#hierarchy-of-exceptions.

Or we could be raising BrokenPipeError / ConnectionResetError (subclasses of ConnectionError) directly.

Note that the docs aready suggest handling OSError (base of ConnectionError) when performing I/O on the server side: https://docs.aiohttp.org/en/stable/web_advanced.html#peer-disconnection. So raising ConnectionError-derived exceptions would be in line with that.


try:
await loop.sendfile(transport, fobj, offset, count)
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3 changes: 2 additions & 1 deletion aiohttp/web_ws.py
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Expand Up @@ -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,
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9 changes: 9 additions & 0 deletions tests/test_web_websocket.py
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Expand Up @@ -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)
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