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match Field TypeVar variance in models.fields.related by asottile · Pull Request #2292 · typeddjango/django-stubs · GitHub
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match Field TypeVar variance in models.fields.related #2292

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Merged
merged 1 commit into from
Jul 30, 2024
Merged

match Field TypeVar variance in models.fields.related #2292

merged 1 commit into from
Jul 30, 2024

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@asottile
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previously failing with:

_____________________________ foreign_key_subclass _____________________________
/home/asottile/workspace/django-stubs/tests/typecheck/fields/test_related.yml:90: 
E   pytest_mypy_plugins.utils.TypecheckAssertionError: Invalid output: 
E   Actual:
E     myapp/models:7: error: Variance of TypeVar "_ST" incompatible with variance in parent type  [type-var] (diff)
E     myapp/models:7: error: Variance of TypeVar "_GT" incompatible with variance in parent type  [type-var] (diff)
E   Expected:
E     (empty)

I'm not sure how this wasn't a problem before 5.0.4 for us but it certainly is now!

I'm also surprised mypy doesn't report this same error for related.pyi itself -- there must be some special-cased rules that .pyi files don't have to follow

@asottile
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failure looks like a github flake

@asottile-sentry asottile-sentry mentioned this pull request Jul 29, 2024
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sobolevn
sobolevn approved these changes Jul 30, 2024
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Thank you!

Source:

django-stubs/django-stubs/db/models/fields/__init__.pyi

Lines 47 to 52 in 04eed10

# __set__ value type
_ST = TypeVar("_ST", contravariant=True)
# __get__ return type
_GT = TypeVar("_GT", covariant=True)
class Field(RegisterLookupMixin, Generic[_ST, _GT]):

@sobolevn sobolevn merged commit 9b50861 into typeddjango:master Jul 30, 2024
@asottile-sentry asottile-sentry mentioned this pull request Jul 31, 2024
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@asottile asottile deleted the foreign-key-variance branch August 4, 2024 19:12
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@asottile @sobolevn