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Document that we can't use new stdlib symbols until added to type-checkers #11903
Description
#11890 (comment)
An unwritten convention (because we've been bitten by it a few times in the past), is to not use newly added symbols from the stdlib stubs until all supported type-checkers (pyright, mypy, pytype??, realistically we're always waiting on mypy release because pyright releases so often) updated their vendored version of typeshed.
This is a suggestion to add this convention to the contributing guideline in a more official way, and to teach contributors about this unobvious gotcha.
Relates to #5835
Activity
srittau commentedon May 12, 2024
One of the ideas behind #5952 was to actually test third-party stubs using the vendored stdlib of the respective type checkers. Maybe we should resurrect that idea?
AlexWaygood commentedon May 12, 2024
I don't think we should only test our third-party stubs against type checkers' vendored stdlib stubs, because it would mean we'd be blind to the impact changes we make to our stdlib stubs would have on our third-party stubs. That would:
[-]Document that we can't use new stdlib symbols until a [/-][+]Document that we can't use new stdlib symbols until added to type-checkers[/+]srittau commentedon Jul 22, 2026
Since there are now at least five type checkers in active development, I propose the following concrete policy: We won't start using symbols from
_typeshedin third-party stubs until at least 60 days have passed since they were added.Add _typeshed cooldown period for 3rd-party stubs