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Mechanism to enable __weakref__ slot on dataclass(slots=True) #91215

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ariebovenberg mannequin opened this issue Mar 18, 2022 · 5 comments
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Mechanism to enable __weakref__ slot on dataclass(slots=True) #91215

ariebovenberg mannequin opened this issue Mar 18, 2022 · 5 comments
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@ericvsmith
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3.11 bug and security fixes stdlib Python modules in the Lib dir type-feature A feature request or enhancement

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@ariebovenberg
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ariebovenberg mannequin commented Mar 18, 2022

BPO 47059
Nosy @ericvsmith, @ariebovenberg

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 = None
closed_at = None
created_at = <Date 2022-03-18.18:00:50.175>
labels = ['library', '3.11']
title = 'Mechanism to enable __weakref__ slot on dataclass(slots=True)'
updated_at = <Date 2022-03-18.18:00:50.175>
user = 'https://github.com/ariebovenberg'

bugs.python.org fields:

activity = <Date 2022-03-18.18:00:50.175>
actor = 'ariebovenberg'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2022-03-18.18:00:50.175>
creator = 'ariebovenberg'
dependencies = []
files = []
hgrepos = []
issue_num = 47059
keywords = []
message_count = 1.0
messages = ['415515']
nosy_count = 2.0
nosy_names = ['eric.smith', 'ariebovenberg']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue47059'
versions = ['Python 3.11']
@ariebovenberg
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ariebovenberg mannequin commented Mar 18, 2022

As discussed in bpo-46382, dataclasses may want to support the __weakref__ slot.

Currently, automatically slotted dataclasses are not given a __weakref__ slot. This makes auto-slotted dataclasses incompatible with weakref.

The attrs library has chosen for the following approeach:

  • when slots are generated, a __weakref__ slot is added by default
  • this may be optionally disabled with the weakref_slot=False flag

See this discussion on why that approach was taken: python-attrs/attrs#420

The question for dataclass is: do we want to follow suit? Or perhaps make __weakref__ slot opt-in instead of opt-out?

@ariebovenberg ariebovenberg mannequin added 3.11 bug and security fixes stdlib Python modules in the Lib dir labels Mar 18, 2022
@ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
@rhettinger
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A weakref slot should be opt-in. No need to make everyone pay for a feature that is so rarely needed.

@ericvsmith
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I agree. I would rather this be weakref_slot=True, which defaults to False.

@ericvsmith ericvsmith self-assigned this Apr 29, 2022
@ericvsmith ericvsmith added the type-feature A feature request or enhancement label Apr 29, 2022
@ericvsmith
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PR #92160

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#92160 was merged to 3.11.

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