Mock autospec does not work with subclasses of property()

[amauryfa]

BPO	26750
Nosy	@gpshead, @amauryfa, @voidspace, @berkerpeksag
Files	mock-descriptor.patch mock-descriptor-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/berkerpeksag'
closed_at = <Date 2016-08-07.16:07:15.175>
created_at = <Date 2016-04-13.22:13:06.644>
labels = ['type-bug', 'library']
title = 'Mock autospec does not work with subclasses of property()'
updated_at = <Date 2016-08-17.22:40:09.697>
user = 'https://github.com/amauryfa'

bugs.python.org fields:

activity = <Date 2016-08-17.22:40:09.697>
actor = 'gregory.p.smith'
assignee = 'berker.peksag'
closed = True
closed_date = <Date 2016-08-07.16:07:15.175>
closer = 'gregory.p.smith'
components = ['Library (Lib)']
creation = <Date 2016-04-13.22:13:06.644>
creator = 'amaury.forgeotdarc'
dependencies = []
files = ['42458', '42891']
hgrepos = []
issue_num = 26750
keywords = ['patch']
message_count = 7.0
messages = ['263361', '265827', '272122', '272124', '272215', '272842', '272997']
nosy_count = 5.0
nosy_names = ['gregory.p.smith', 'amaury.forgeotdarc', 'michael.foord', 'python-dev', 'berker.peksag']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue26750'
versions = ['Python 3.5', 'Python 3.6']

[amauryfa]

When patching a class, mock.create_autospec() correctly detects properties and __slot__ attributes, but not subclasses of property() or other kinds of data descriptors.

The attached patch detects all data descriptors and patch them the way they should be.

[amauryfa]

Updated patch with review comments.

[python-dev]

New changeset e947248100ae by Gregory P. Smith in branch '3.5':
Issue bpo-26750: unittest.mock.create_autospec() now works properly
https://hg.python.org/cpython/rev/e947248100ae

New changeset 0bc14c91ef7e by Gregory P. Smith in branch 'default':
Issue bpo-26750: unittest.mock.create_autospec() now works properly for
https://hg.python.org/cpython/rev/0bc14c91ef7e

[berkerpeksag]

Thanks! Is there a reason not to use inspect.isdatadescriptor() instead of _is_data_descriptor()?

[gpshead]

Probably just Amaury and I forgetting that existed. Amaury, inspect.isdatadescriptor's implementation is a bit different than this change's _is_data_descriptor. Thoughts?

[python-dev]

New changeset 3ff02380b1bf by Gregory P. Smith in branch '3.5':
Issue bpo-26750: use inspect.isdatadescriptor instead of our own
https://hg.python.org/cpython/rev/3ff02380b1bf

New changeset d51a66622266 by Gregory P. Smith in branch 'default':
Issue bpo-26750: use inspect.isdatadescriptor instead of our own
https://hg.python.org/cpython/rev/d51a66622266

[amauryfa]

inspect.isdatadescriptor() is better indeed.
(I was initially working on an old version of mock.py which does not import inspect, and I did not want to add the dependency there).

• inspect uses hasattr(type(obj)) instead of hasatr(obj). This is better, (but does not work for 2.x old-style classes)

• my patch tested for __del__... this is completely wrong, it should have been __delete__. oops.
  inspect.isdatadescriptor() does not test for __delete__. This is insaccurate, but I doubt it will ever matter. This is only possible for Python-defined descriptors, the C implementation always exposes both __set__ and __delete__ when tp_set is filled.

IOW, I'm happy with the current state.