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Mike Bayer
c86ebb0a99
A significant behavioral change has been made to the behavior of the :paramref:`_orm.mapped_column.default` and :paramref:`_orm.relationship.default` parameters, when used with SQLAlchemy's :ref:`orm_declarative_native_dataclasses` feature introduced in 2.0, where the given value (assumed to be an immutable scalar value) is no longer passed to the ``@dataclass`` API as a real default, instead a token that leaves the value un-set in the object's ``__dict__`` is used, in conjunction with a descriptor-level default. This prevents an un-set default value from overriding a default that was actually set elsewhere, such as in relationship / foreign key assignment patterns as well as in :meth:`_orm.Session.merge` scenarios. See the full writeup in the :ref:`whatsnew_21_toplevel` document which includes guidance on how to re-enable the 2.0 version of the behavior if needed. This adds a new implicit default field to ScalarAttributeImpl so that we can have defaults that are not in the dictionary but are instead passed through to the class-level descriptor, effectively allowing custom defaults that are not used in INSERT or merge Fixes: #12168 Change-Id: Ia327d18d6ec47c430e926ab7658e7b9f0666206e