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gh-85795: Raise a clear error when`super()` is used in`typing.NamedTuple` subclasses#130082

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JelleZijlstra merged 3 commits intopython:mainfrom

johnslavik:eligible-classcell-error-message

Mar 6, 2025

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gh-85795: Raise a clear error when`super()` is used in`typing.NamedTuple` subclasses#130082
JelleZijlstra merged 3 commits intopython:mainfrom
johnslavik:eligible-classcell-error-message

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johnslavik commentedFeb 13, 2025•
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Follow-up to conclusions fromgh-129352,closesgh-85795.

In#129352 (comment),@rhettinger and I agreed that a clear error message is needed when a user attempts to usesuper() intyping.NamedTuple subclasses.

~~I believe this PR should be backported.~~ Since we no longer raise aRuntimeError, this cannot be backported.

About the PR

Pure presence of__classcell__ is enough to confirm that__class__ closure was created to enablesuper() calls.

Tests for cases where__classcell__ are manually set in typed named tuples were intentionallynot added, as I don't see the value in considering these behaviors.

Interestingly, I used a note admonition instead of.. versionchanged:: next in the docs and it's completely backward-compatible: it applies to all relevant previous versions of Python. I considered making an "important" block instead, but I thinksuper() is not often enough to support that idea. No longer true, we raiseTypeError instead ofRuntimeError

CC previous reviewers:@ZeroIntensity @AlexWaygood @JelleZijlstra @rhettinger

Issue:__class__ not set in typing.NamedTuple #85795

📚 Documentation preview 📚:https://cpython-previews--130082.org.readthedocs.build/

johnslavik requested review fromAlexWaygood andJelleZijlstra ascode owners

February 13, 2025 14:23

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Feb 13, 2025

__class__ not set in typing.NamedTuple#85795

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Feb 13, 2025

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Reminder to change to TypeError

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bedevere-appbot commentedMar 3, 2025

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phraseI have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.