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dataclass(slots=True) incompatible with __init_subclass__ #91126
Description
| BPO | 46970 |
|---|---|
| Nosy | @ericvsmith, @crusaderky |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = 'https://github.com/ericvsmith'
closed_at = None
created_at = <Date 2022-03-10.00:14:28.417>
labels = ['type-bug', 'library', '3.10']
title = 'dataclass(slots=True) incompatible with __init_subclass__'
updated_at = <Date 2022-03-10.00:28:03.767>
user = 'https://github.com/crusaderky'bugs.python.org fields:
activity = <Date 2022-03-10.00:28:03.767>
actor = 'eric.smith'
assignee = 'eric.smith'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2022-03-10.00:14:28.417>
creator = 'crusaderky'
dependencies = []
files = []
hgrepos = []
issue_num = 46970
keywords = []
message_count = 2.0
messages = ['414822', '414823']
nosy_count = 2.0
nosy_names = ['eric.smith', 'crusaderky']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue46970'
versions = ['Python 3.10']
Activity
crusaderky commentedon Mar 10, 2022
Related to bpo-46382
A class decorated with dataclass(slots=True) can't pass any parameters to the __init_subclass__ method of its parent class.
File "lib/python3.10/dataclasses.py", line 1145, in _add_slots
cls = type(cls)(cls.__name__, cls.__bases__, cls_dict)
TypeError: A.__init_subclass__() missing 1 required positional argument: 'msg'
ericvsmith commentedon Mar 10, 2022
This appears to be due to dataclasses needing to create a new class in order to set __slots__. I'll look at it, but I doubt there's anything that can be done.
attrs has the same issue:
File "xxxxx/.local/lib/python3.8/site-packages/attr/make.py", line 889, in _create_slots_class
cls = type(self._cls)(self._cls.__name_, self._cls.__bases__, cd)
TypeError: __init_subclass__() missing 1 required positional argument: 'msg'
fix: make compatible with python3.10
sobolevn commentedon Aug 23, 2024
I think that we should add this case to the docs. Because there's really nothing we can do to support this case.
Solutions:
slots=True, write manual slots__init_subclass__I will send a PR with the proposed note about that.
pythongh-91126: Docs and tests for slotted dataclasses with `__init_s…
gh-91126: Docs and tests for slotted dataclasses with `__init_subclas…
pythongh-91126: Docs and tests for slotted dataclasses with `__init_s…
pythongh-91126: Docs and tests for slotted dataclasses with `__init_s…
[3.12] gh-91126: Docs and tests for slotted dataclasses with `__init_…
[3.13] gh-91126: Docs and tests for slotted dataclasses with `__init_…