diff options
Diffstat (limited to 'doc/build/orm/dataclasses.rst')
| -rw-r--r-- | doc/build/orm/dataclasses.rst | 49 |
1 files changed, 5 insertions, 44 deletions
diff --git a/doc/build/orm/dataclasses.rst b/doc/build/orm/dataclasses.rst index 6285ddef7..bbd05fcd5 100644 --- a/doc/build/orm/dataclasses.rst +++ b/doc/build/orm/dataclasses.rst @@ -37,53 +37,14 @@ as having Dataclass-specific behaviors, most notably by taking advantage of :pe as though it were explicitly decorated using the ``@dataclasses.dataclass`` decorator. -.. note:: Support for :pep:`681` in typing tools as of **March 11, 2023** is - limited and is currently known to be supported by Pyright_, but - **not correctly supported** by Mypy_ version 1.1.1. Mypy 1.1.1 introduced - :pep:`681` support but failed to accommodate for Python descriptors - correctly (see Github issue below). - - In order to resolve errors when using :class:`_orm.MappedAsDataclass` with - Mypy version 1.1.1 or other typing tools that have similar errors, the - following workaround may be used, which uses a plain non-pep681 mixin within - ``TYPE_CHECKING`` to avoid errors:: - - import typing - - if typing.TYPE_CHECKING: - - class MappedAsDataclass: - """Mixin class which works in the same way as - :class:`_orm.MappedAsDataclass`, - but does not include :pep:`681` directives. - - """ - - def __init__(self, *arg: typing.Any, **kw: typing.Any): - pass - - else: - from sqlalchemy.orm import MappedAsDataclass - - Above, the SQLAlchemy :class:`_orm.MappedAsDataclass` mixin is hidden - from typing tools and replaced with a plain mixin that sets up an - ``__init__`` constructor that accommodates any arguments. - - When using the :meth:`_orm.registry.mapped_as_dataclass` method, - similar approaches can be taken using a plain decorator, however classes - would need to also include an explicit ``__init__()`` method on a mixin - like the one indicated above for the workaround to work completely:: - - - def mapped_as_dataclass(registry, cls, **kw): - """Will conceal the pep-681 enabled methods from typing tools""" - - return registry.mapped_as_dataclass(cls, **kw) +.. note:: Support for :pep:`681` in typing tools as of **April 4, 2023** is + limited and is currently known to be supported by Pyright_ as well + as Mypy_ as of **version 1.2**. Note that Mypy 1.1.1 introduced + :pep:`681` support but did not correctly accommodate Python descriptors + which will lead to errors when using SQLAlhcemy's ORM mapping scheme. .. seealso:: - https://github.com/python/mypy/issues/13856 - Mypy issue on github - https://peps.python.org/pep-0681/#the-dataclass-transform-decorator - background on how libraries like SQLAlchemy enable :pep:`681` support |