Description

adriangb

opened on Apr 17, 2023

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This was fixed on 3.9 (by #23294 or followups). Here's a test / example:

from enum import Enum
from typing import Literal, Union, get_args


class MyEnum(int, Enum):
    foo = 1

tp = Union[Literal[MyEnum.foo], Literal[1]]
assert len(get_args(tp)) == 2, get_args(tp)

tp = Union[Literal[1], Literal[MyEnum.foo]]
assert len(get_args(tp)) == 2, get_args(tp)

These assertions fail on 3.8 since Union deduplicates both Literals into the same thing. The reason you need Literal here is because enum values are values not types so they can only appear in a Union if they're also within a Literal.

As per #23294 (comment) maybe the answer here is to not do anything. And in fact I looked into back porting and it was too big of a change to be called a back port. But I didn't see this specific issue w/ Enum and Union reported, so I at least wanted to report it and confirm that it is a bug.

Linked PRs

• gh-103592: Add tests of Literal with Enum and Union of Literals #103706
• [3.11] gh-103592: Add tests of Literal with Enum and Union of Literals (GH-103706) #103720

Activity

1. adriangb

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Apr 17, 2023
2. JelleZijlstra commented on Apr 17, 2023

   

   JelleZijlstra

   on Apr 17, 2023

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   3.8 is in security fix-only mode, so it's too late to fix this.

   Reacted by Adrian Garcia Badaracco
3. adriangb commented on Apr 17, 2023

   

   adriangb

   on Apr 17, 2023

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   Makes sense. I'll just close the issue then.
4. adriangb

   closed this as completedon Apr 17, 2023
5. adriangb commented on Apr 17, 2023

   

   adriangb

   on Apr 17, 2023

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   Do you think we can change https://github.com/python/typing_extensions/blob/501a00e4701185ec93220155a0caa3da71d327e8/src/typing_extensions.py#L264-L268 to use the typing-extensions implementation for 3.8 as well?
6. JelleZijlstra commented on Apr 17, 2023

   

   JelleZijlstra

   on Apr 17, 2023

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   Yes, that makes sense to do.
7. sobolevn commented on Apr 23, 2023

   

   sobolevn

   on Apr 23, 2023

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   test_typing.py police is here 🚨

   This is not tested right now, in fact, Literal with enum is never tested at all.
   Moreover, we don't have a single Union[Literal, Literal, ...] test as well.

   Thanks a lot @adriangb for raising this.
   PR with the fix is ready :)
8. sobolevn

   reopened this on Apr 23, 2023
9. sobolevn

   added a commit that references this issue on Apr 23, 2023

   pythongh-103592: Add tests of `Literal` with `Enum` and `Union` of `L…

   e9ccdcc
10. AlexWaygood

    added

    topic-typing

    on Apr 23, 2023
11. AlexWaygood

    added a commit that references this issue on Apr 23, 2023

    gh-103592: Add tests of `Literal` with `Enum` and `Union` of `Literal…

    5041c2b
12. miss-islington

    added a commit that references this issue on Apr 23, 2023

    pythongh-103592: Add tests of `Literal` with `Enum` and `Union` of `L…

    14db874
13. AlexWaygood

    added a commit that references this issue on Apr 23, 2023

    [3.11] gh-103592: Add tests of `Literal` with `Enum` and `Union` of `…

    4e9635e
14. AlexWaygood

    closed this as completedon Apr 23, 2023

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