Fix compatibility issues with django-modeltranslation #649
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…nager mixins - Added a new class `_GenericMixin` to serve as a runtime placeholder for `Generic[ModelT]`. This change prevents `TypeError` during `__class__` assignments, which was an issue when mixins inherited from `Generic[T]` at runtime. - All manager mixins have been updated to inherit from `_GenericMixin` instead of `Generic[ModelT]`. This ensures compatibility with `django-modeltranslation`. - Introduced regressions tests to confirm that the manager instances support `__class__` reassignment without issues. Tests were added for `SoftDeletableManager`, `InheritanceManager`, `QueryManager`, and `JoinManager`. Closes GH-jazzband#636.
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Problem
When using
django-model-utilstogether withdjango-modeltranslation, registering a model that usesSoftDeletableModel(or other models using manager mixins) causes a TypeError during app initialization:This occurs because
django-modeltranslationpatches manager classes by reassigningmanager.__class__to a dynamically created subclass. Python's__class__assignment has strict layout compatibility requirements, and theGeneric[ModelT]base class in our manager mixins causes a layout mismatch.Fixes #636
Solution
Move the
Generic[ModelT]inheritance behindTYPE_CHECKINGso it's only present during static type analysis, not at runtime. At runtime, a simple placeholder class_GenericMixinis used instead.Commandments
CHANGES.rstfile to describe the changes, and quote according issue withGH-<issue_number>.