[New-bugs-announce] [issue40802] AbstractEventLoop.shutdown_default_executor breaks backwards compatibility

[Petr Viktorin]

New submission from Petr Viktorin <encukou at gmail.com>:

In bpo-34037, AbstractEventLoop gained a new abstract method, shutdown_default_executor:
https://docs.python.org/dev/library/asyncio-eventloop.html#asyncio.loop.shutdown_default_executor

All AbstractEventLoop subclasses need to define this method, otherwise they are not compatible with Python 3.9's asyncio. It seems that the anyio and uvloop projects are affected: https://github.com/agronholm/anyio/issues/110

This is mentioned in What's New: https://docs.python.org/dev/whatsnew/3.9.html#changes-in-the-python-api

I'd like to make extra sure asyncio experts know about this backwards incompatibility.
Since asyncio is no longer provisional, should it break backwards compatibility with just a What's New entry?

----------
components: asyncio
messages: 370182
nosy: asvetlov, petr.viktorin, yselivanov
priority: normal
severity: normal
status: open
title: AbstractEventLoop.shutdown_default_executor breaks backwards compatibility
versions: Python 3.9

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<https://bugs.python.org/issue40802>
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