__doc__ attribute is not set in property-derived classes

[sizmailov]

BPO	41287
Nosy	@rhettinger, @tirkarthi, @sizmailov
PRs	bpo-41287: Handle doc argument of property.__init__ in subclasses #23205

^{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 2020-07-12.20:34:43.594>
labels = []
title = '__doc__ attribute is not set in property-derived classes'
updated_at = <Date 2020-11-09.10:20:58.378>
user = 'https://github.com/sizmailov'

bugs.python.org fields:

activity = <Date 2020-11-09.10:20:58.378>
actor = 'Sergei Izmailov'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2020-07-12.20:34:43.594>
creator = 'Sergei Izmailov'
dependencies = []
files = []
hgrepos = []
issue_num = 41287
keywords = ['patch']
message_count = 3.0
messages = ['373571', '373624', '373627']
nosy_count = 3.0
nosy_names = ['rhettinger', 'xtreak', 'Sergei Izmailov']
pr_nums = ['23205']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue41287'
versions = []

[sizmailov]

MRE:

class Property(property):
    pass

print(Property(None, None, None, "hello").__doc__)

Expected:
hello

Actual:
None

[rhettinger]

What would you expect this to print?

class Property(property):
    'custom docstring'

print(Property(None, None, None, "hello").__doc__)

[sizmailov]

class Property(property):
    'custom docstring'

print(Property(None, None, None, "hello").__doc__)

This snippet is expected to print "hello" as well (at least it's what comment in cpython implementation suggests)

https://github.com/python/cpython/blob/master/Objects/descrobject.c#L1712-L1715