weakref.ref ignores a 'callback' keyword argument

[mdickinson]

BPO	17765
Nosy	@birkenfeld, @mdickinson, @pitrou, @serhiy-storchaka
Files	no_weakref_kwargs.patch no_weakref_kwargs_2.patch

^{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/birkenfeld'
closed_at = <Date 2016-05-07.12:48:00.102>
created_at = <Date 2013-04-16.19:11:10.329>
labels = ['extension-modules', 'type-bug']
title = "weakref.ref ignores a 'callback' keyword argument"
updated_at = <Date 2016-05-07.12:48:00.101>
user = 'https://github.com/mdickinson'

bugs.python.org fields:

activity = <Date 2016-05-07.12:48:00.101>
actor = 'serhiy.storchaka'
assignee = 'georg.brandl'
closed = True
closed_date = <Date 2016-05-07.12:48:00.102>
closer = 'serhiy.storchaka'
components = ['Extension Modules']
creation = <Date 2013-04-16.19:11:10.329>
creator = 'mark.dickinson'
dependencies = []
files = ['32118', '32119']
hgrepos = []
issue_num = 17765
keywords = ['patch']
message_count = 8.0
messages = ['187115', '199898', '199904', '199909', '264954', '265056', '265062', '265063']
nosy_count = 5.0
nosy_names = ['georg.brandl', 'mark.dickinson', 'pitrou', 'python-dev', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue17765'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6']

[mdickinson]

Passing a weakref.ref callback by keyword currently fails silently:

Python 3.4.0a0 (default:537c1f1ab53c, Apr 16 2013, 20:07:47) 
[GCC 4.2.1 (Apple Inc. build 5664)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import weakref
>>> weakref.ref({1, 2, 3}, callback=lambda ref:print("collected"))
<weakref at 0x1006189d8; dead>

For Python 3.4, I'd suggest that either (1) this should be an exception, or (2) it should be permissible to pass the callback by keyword.

[birkenfeld]

See attached patch, it handles this like all other builtins that don't support keyword arguments in their constructor.

[pitrou]

Why the PyWeakref_Check() in your patch?

[birkenfeld]

Good point, that is pointless in __init__().

[serhiy-storchaka]

no_weakref_kwargs_2.patch LGTM.

[birkenfeld]

Serhiy, feel free to go ahead and commit, I don't have my keys with me ATM.

[python-dev]

New changeset ee17a83feabc by Serhiy Storchaka in branch '3.5':
Issue bpo-17765: weakref.ref() no longer silently ignores keyword arguments.
https://hg.python.org/cpython/rev/ee17a83feabc

New changeset 60de9c6188cc by Serhiy Storchaka in branch '2.7':
Issue bpo-17765: weakref.ref() no longer silently ignores keyword arguments.
https://hg.python.org/cpython/rev/60de9c6188cc

New changeset ef55fa8c4b82 by Serhiy Storchaka in branch 'default':
Issue bpo-17765: weakref.ref() no longer silently ignores keyword arguments.
https://hg.python.org/cpython/rev/ef55fa8c4b82

[serhiy-storchaka]

Done. This issue is similar to recently closed bpo-26822.

Please give me know if you have other ready to review patches.