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UDPTransport returning when data is empty

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
42/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Stale
Tech stack
python
Domain
networking

Research direction

Start at uvloop/handles/udp.pyx lines 284-286, where UDPTransport currently returns for empty data, and compare the referenced CPython 3.13 change. Done means sendto no longer ignores zero-length datagrams while preserving the documented asyncio transport behavior.

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Description

  • uvloop version:
  • Python version: <3.13
  • Platform: MacOS
  • Can you reproduce the bug with PYTHONASYNCIODEBUG in env?:
  • Does uvloop behave differently from vanilla asyncio? How?: There is a change made in CPython 3.13 to remove this behaviour.

The Datagram transport in both asyncio.DatagramTransport and uvloop.UDPTransport will return and ignore calls to sendto if the data is empty. This prohibits users from sending zero-length datagrams.

The behaviour will be removed in CPython 3.13 (see https://github.com/python/cpython/issues/113812). Note that the public API in uvloop references the Python asyncio behaviour.

https://github.com/MagicStack/uvloop/blob/6c770dc3fbdd281d15c2ad46588c139696f9269c/uvloop/handles/udp.pyx#L284-L286

Dominant language
Cython
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