Fix data descriptor detection in inspect.getattr_static

[davidhalter]

BPO	31184
Nosy	@rhettinger, @serhiy-storchaka
Superseder	bpo-26103: Contradiction in definition of "data descriptor" between (dotted lookup behavior/datamodel documentation) and (inspect lib/descriptor how-to)
Files	0001-Fix-data-descriptor-detection-in-inspect.getattr_sta.patch: Potential patch that fixes the issue

^{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 2017-08-11.16:22:11.131>
labels = ['type-bug', 'library', '3.11']
title = 'Fix data descriptor detection in inspect.getattr_static'
updated_at = <Date 2021-12-08.04:22:58.232>
user = 'https://bugs.python.org/davidhalter'

bugs.python.org fields:

activity = <Date 2021-12-08.04:22:58.232>
actor = 'rhettinger'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2017-08-11.16:22:11.131>
creator = 'davidhalter'
dependencies = []
files = ['47078']
hgrepos = []
issue_num = 31184
keywords = ['patch']
message_count = 4.0
messages = ['300170', '300173', '407976', '407985']
nosy_count = 3.0
nosy_names = ['rhettinger', 'serhiy.storchaka', 'davidhalter']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'resolved'
status = 'open'
superseder = '26103'
type = 'behavior'
url = 'https://bugs.python.org/issue31184'
versions = ['Python 3.11']

Linked PRs

• gh-75367: fix data descriptor detection in inspect.getattr_static #104517
• [3.11] gh-75367: Fix data descriptor detection in inspect.getattr_static (GH-104517) #104557

[davidhalter]

inspect.getattr_static is currently not identifying data descriptors the right way.

Data descriptors are defined by having a __get__ attribute and at least one of the __set__ and __delete__ attributes.

Implementation detail: Both __delete__ and __get__ set the same slot called tp_descr_set in CPython.

I have attached a patch that fixes the issue IMO.

[serhiy-storchaka]

See also bpo-26103.

[davidhalter]

This is not a duplicate. It is related to https://bugs.python.org/issue26103, because __get__ is not required anymore for an object to be a data descriptor. The current code on master (of inspect.getattr_static) still thinks a descriptor has both __get__ and __set__ set.

Since issue bpo-26103 has been fixed, it's now clear that my patch is slightly wrong, but I'm happy to fix that if someone is actually going to review it.

[rhettinger]

Can you give an example of where getattr_static() is not doing what you expect?