isinstance(x, typing.Protocol-class) unexpectedly evaluates properties

[daitakahashi]

BPO	45282
Nosy	@AlexWaygood, @daitakahashi
Files	test_protocol_property.py: testcases

^{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 2021-09-24.13:25:14.862>
labels = ['type-bug', '3.8', '3.9']
title = 'isinstance(x, typing.Protocol-class) unexpectedly evaluates properties'
updated_at = <Date 2021-09-24.14:52:18.540>
user = 'https://github.com/daitakahashi'

bugs.python.org fields:

activity = <Date 2021-09-24.14:52:18.540>
actor = 'AlexWaygood'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2021-09-24.13:25:14.862>
creator = 'daitakahashi'
dependencies = []
files = ['50303']
hgrepos = []
issue_num = 45282
keywords = []
message_count = 2.0
messages = ['402562', '402567']
nosy_count = 2.0
nosy_names = ['AlexWaygood', 'daitakahashi']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45282'
versions = ['Python 3.8', 'Python 3.9']

[daitakahashi]

Because __instancecheck__ of _ProtocolMeta uses hasattr() and getattr(), both of which evaluate property attributes, calling isinstance() with an object and a class that inherits typing.Protocol evaluates the input object's properties in some cases.

The attached testcases include three cases of checking subtype relationship of an instance (having a property "x" that may raise RuntimeError on evaluation) and following three protocol classes;
(1) a protocol class having "x" as a property,
(2) a protocol class having "x" as a data attribute, and
(3) a protocol class having "x" as a class property that raises
RuntimeError on evaluation (>= python 3.9 only).

Expected behavior:

1. The isinstance(obj, Protocol_class) does not evaluate anything but just checks existence of attribute names.
2. All cases in the attached testcases run without any error

Thank you very much in advance.

[AlexWaygood]

Related: https://bugs.python.org/issue44904

[AlexWaygood]

Duplicate of #102433, which is a newer issue but has more discussion