https://github.com/python/cpython/commit/75e72822a390df81ca11355d8e0aac88e4046c27
commit: 75e72822a390df81ca11355d8e0aac88e4046c27
branch: main
author: sobolevn <[email protected]>
committer: sobolevn <[email protected]>
date: 2024-09-01T13:25:34+03:00
summary:
gh-91126: Docs and tests for slotted dataclasses with `__init_subclass__`
(#123342)
files:
M Doc/library/dataclasses.rst
M Lib/test/test_dataclasses/__init__.py
diff --git a/Doc/library/dataclasses.rst b/Doc/library/dataclasses.rst
index c892c5cb1ff566..324403f87b9f91 100644
--- a/Doc/library/dataclasses.rst
+++ b/Doc/library/dataclasses.rst
@@ -185,10 +185,21 @@ Module contents
- *slots*: If true (the default is ``False``), :attr:`~object.__slots__`
attribute
will be generated and new class will be returned instead of the original
one.
If :attr:`!__slots__` is already defined in the class, then
:exc:`TypeError`
- is raised. Calling no-arg :func:`super` in dataclasses using
``slots=True`` will result in
- the following exception being raised:
- ``TypeError: super(type, obj): obj must be an instance or subtype of
type``.
- The two-arg :func:`super` is a valid workaround. See :gh:`90562` for full
details.
+ is raised.
+
+ .. warning::
+ Calling no-arg :func:`super` in dataclasses using ``slots=True``
+ will result in the following exception being raised:
+ ``TypeError: super(type, obj): obj must be an instance or subtype of
type``.
+ The two-arg :func:`super` is a valid workaround.
+ See :gh:`90562` for full details.
+
+ .. warning::
+ Passing parameters to a base class :meth:`~object.__init_subclass__`
+ when using ``slots=True`` will result in a :exc:`TypeError`.
+ Either use ``__init_subclass__`` with no parameters
+ or use default values as a workaround.
+ See :gh:`91126` for full details.
.. versionadded:: 3.10
diff --git a/Lib/test/test_dataclasses/__init__.py
b/Lib/test/test_dataclasses/__init__.py
index b93c99d8c90bf3..da696ad961cfd7 100644
--- a/Lib/test/test_dataclasses/__init__.py
+++ b/Lib/test/test_dataclasses/__init__.py
@@ -3664,6 +3664,38 @@ class A(WithDictSlot): ...
self.assertEqual(A().__dict__, {})
A()
+ @support.cpython_only
+ def test_slots_with_wrong_init_subclass(self):
+ # TODO: This test is for a kinda-buggy behavior.
+ # Ideally, it should be fixed and `__init_subclass__`
+ # should be fully supported in the future versions.
+ # See https://github.com/python/cpython/issues/91126
+ class WrongSuper:
+ def __init_subclass__(cls, arg):
+ pass
+
+ with self.assertRaisesRegex(
+ TypeError,
+ "missing 1 required positional argument: 'arg'",
+ ):
+ @dataclass(slots=True)
+ class WithWrongSuper(WrongSuper, arg=1):
+ pass
+
+ class CorrectSuper:
+ args = []
+ def __init_subclass__(cls, arg="default"):
+ cls.args.append(arg)
+
+ @dataclass(slots=True)
+ class WithCorrectSuper(CorrectSuper):
+ pass
+
+ # __init_subclass__ is called twice: once for `WithCorrectSuper`
+ # and once for `WithCorrectSuper__slots__` new class
+ # that we create internally.
+ self.assertEqual(CorrectSuper.args, ["default", "default"])
+
class TestDescriptors(unittest.TestCase):
def test_set_name(self):
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