Add __orig_bases__ to TypedDict

[adriangb]

No description provided.

[adriangb]

This should be up to date with the CPython change which just got merged

[JelleZijlstra]

Thanks! Could you also add a CHANGELOG entry? Look at some of Alex's recent PRs for examples.

[AlexWaygood]

We need to change these lines so that we reimplement NamedTuple on <=3.11 rather than <=3.10. Otherwise call-based typing_extensions.NamedTuples will have __orig_bases__ on 3.7-3.10 and 3.12+, but not 3.11 😄

typing_extensions/src/typing_extensions.py

Lines 2316 to 2320 in fb37b2e

	# Backport typing.NamedTuple as it exists in Python 3.11.
	# In 3.11, the ability to define generic `NamedTuple`s was supported.
	# This was explicitly disallowed in 3.9-3.10, and only half-worked in <=3.8.
	if sys.version_info >= (3, 11):
	NamedTuple = typing.NamedTuple

test_typing_extensions_defers_when_possible will need to be adjusted as a result -- you'll need to move "NamedTuple" into the if sys.version_info < (3, 12) set here:

typing_extensions/src/test_typing_extensions.py

Lines 3610 to 3613 in fb37b2e

	if sys.version_info < (3, 11):
	exclude |= {'final', 'NamedTuple', 'Any'}
	if sys.version_info < (3, 12):
	exclude |= {'Protocol', 'runtime_checkable', 'SupportsIndex'}

[adriangb]

Could you also add a CHANGELOG entry?

Done, I copied Alex's changelog note from CPython.

[AlexWaygood]

I think it's important that we copy CPython's behaviour here, and CPython emits a deprecation warning here on 3.11+. This PR means we reimplement TypedDict on 3.11 now, so the change is needed, I think. @JelleZijlstra do you think we should only emit the deprecation warning if the user is running typing_extensions on 3.11+? (Referencing #150 (comment))

[JelleZijlstra]

That's a hard question and gets into what we would do if we ever want to break backwards compatibility for typing-extensions. My first instinct is to say we should always warn in typing-extensions, regardless of the version, but then what would we do when CPython removes support for kwargs-based TypedDicts? I'd be hesitant to remove the runtime behavior in typing-extensions and break backwards compatibility.

[AlexWaygood]

I agree it's a hard question.

Elsewhere in the typing_extensions implementation of TypedDict, we actually already have two places where CPython long ago removed support for a certain feature, but typing_extensions has in effect had "eternal deprecation warnings":

typing_extensions/src/typing_extensions.py

Lines 789 to 791 in fb37b2e

	import warnings
	warnings.warn("Passing '_typename' as keyword argument is deprecated",
	DeprecationWarning, stacklevel=2)

typing_extensions/src/typing_extensions.py

Lines 804 to 806 in fb37b2e

	import warnings
	warnings.warn("Passing '_fields' as keyword argument is deprecated",
	DeprecationWarning, stacklevel=2)

[JelleZijlstra]

I think eternal deprecation warnings might be the right answer, actually. (Or eternal until we ever make typing-extensions 5 in the distant uncertain future.)

[AlexWaygood]

So maybe we do want the change in #150 (comment)? ;)

[JelleZijlstra]

Yes, let's do that. I commented there because the change looked unrelated to this PR.

[AlexWaygood]

I filed adriangb#2 as a PR to your branch to address my comment above here: #150 (review)

[AlexWaygood]

Looks great to me!