While I have not been involved in the release process for like 15 years or more, I would like to point out that breaking changes mean the distros are less likely to ship them, and be less likely to trust updates.
Trying to get RH &c to stop shipping 1.5.2 was a huge effort. Always, any time when you might need to break compat it's a huge risk. On Wed, 21 Apr 2021, 4:58 am Thomas Wouters, <tho...@python.org> wrote: > > (Starting a new thread so as not to derail any of the ongoing discussions.) > > Thanks, everyone, for your thoughts on Python 3.10 and the impact of PEP > 563 (postponed evaluation of annotations) becoming the default. The > Steering Council has considered the issue carefully, along with many of the > proposed alternatives and solutions, and we’ve decided that at this point, > we simply can’t risk the compatibility breakage of PEP 563. We need to roll > back the change that made stringified annotations the default, at least for > 3.10. (Pablo is already working on this.) > > To be clear, we are not reverting PEP 563 itself. The future import will > keep working like it did since Python 3.7. We’re delaying making PEP 563 > string-based annotations the default until Python 3.11. This will give us > time to find a solution that works for everyone (or to find a feasible > upgrade path for users who currently rely on evaluated annotations). Some > considerations that led us to this decision: > > - PEP 563’s default change is clearly too disruptive to downstream users > and third-party libraries to happen right now. We can’t risk breaking even > a small subset of the FastAPI/pydantic users, not to mention other uses of > evaluated type annotations that we’re not aware of yet. > - PEP 563 provides no warning to users of the feature it’s disabling. > Without that, we can’t expect users to be aware of the upcoming breakage. > The lack of a warning was by design, and made sense in a world where type > annotations were only consumed by static type checkers --- but that’s not > actually the situation we’re in. There are clearly existing real-world, > run-time uses of type annotations that would be adversely affected by this > change. > - Originally, PEP 563 was scheduled to take effect in Python 4, and this > changed recently (after the discussion in the Language Summit of 2020). > It's possible that third-party libraries and users didn’t plan to react in > the current time frame as they were not aware of this change in timing. > - There isn’t enough time to properly discuss PEP 649 or any of the > alternatives before the beta 1 deadline, and we really need to make sure we > don’t compound errors here. We need to look for a long term solution, > which isn’t possible while still maintaining the release deadlines of > Python 3.10. That means we’re also deferring PEP 649 to Python 3.11. > > In the Steering Council’s unanimous opinion, rolling back the default flip > for stringified annotations in Python 3.10 is the least disruptive of all > the options. > > We need to continue discussing the issue and potential solutions, since > this merely postpones the problem until 3.11. (For the record, postponing > the change further is not off the table, either, for example if the final > decision is to treat evaluated annotations as a deprecated feature, with > warnings on use.) > > For what it’s worth, the SC is also considering what we can do to reduce > the odds of something like this happening again, but that’s a separate > consideration, and a multi-faceted one at that. > > For the Steering Council, > Thomas. > -- > Thomas Wouters <tho...@python.org> > > Hi! I'm an email virus! Think twice before sending your email to help me > spread! > _______________________________________________ > python-committers mailing list -- python-committ...@python.org > To unsubscribe send an email to python-committers-le...@python.org > https://mail.python.org/mailman3/lists/python-committers.python.org/ > Message archived at > https://mail.python.org/archives/list/python-committ...@python.org/message/CLVXXPQ2T2LQ5MP2Y53VVQFCXYWQJHKZ/ > Code of Conduct: https://www.python.org/psf/codeofconduct/ >
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