Subclassing Protocol get different __init__

[uriyyo]

BPO	44806
Nosy	@ambv, @serhiy-storchaka, @miss-islington, @uriyyo, @Fidget-Spinner
PRs	bpo-44806: Fix issue with typing.Protocol __init__ method generation #27541 bpo-44806: Fix __init__ in subclasses of protocols #27545 [3.10] bpo-44806: Fix __init__ in subclasses of protocols (GH-27545) #27558 [3.9] bpo-44806: Fix __init__ in subclasses of protocols (GH-27545) #27559 bpo-44807: Forbid to define __init__ method in Protocol classes #27543

^{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 = <Date 2021-08-02.17:37:34.149>
created_at = <Date 2021-08-02.09:20:47.665>
labels = ['type-bug', 'library', '3.9', '3.10', '3.11']
title = 'Subclassing Protocol get different __init__'
updated_at = <Date 2021-08-02.17:37:34.149>
user = 'https://github.com/uriyyo'

bugs.python.org fields:

activity = <Date 2021-08-02.17:37:34.149>
actor = 'lukasz.langa'
assignee = 'none'
closed = True
closed_date = <Date 2021-08-02.17:37:34.149>
closer = 'lukasz.langa'
components = ['Library (Lib)']
creation = <Date 2021-08-02.09:20:47.665>
creator = 'uriyyo'
dependencies = []
files = []
hgrepos = []
issue_num = 44806
keywords = ['patch']
message_count = 5.0
messages = ['398736', '398756', '398780', '398782', '398785']
nosy_count = 5.0
nosy_names = ['lukasz.langa', 'serhiy.storchaka', 'miss-islington', 'uriyyo', 'kj']
pr_nums = ['27541', '27545', '27558', '27559', '27543']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue44806'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[uriyyo]

When we subclassing Protocol, we get a __init__ differing from default one but the protocol in question didn't define any __init__.

More information can be found here - python/typing#644

[serhiy-storchaka]

There is other related case:

>>> from typing import *
>>> class P(Protocol): pass
... 
>>> class B:
...     def __init__(self):
...         self.test = 'OK'
... 
>>> class D(P, B):
...     pass
... 
>>> D().test
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'D' object has no attribute 'test'

[ambv]

New changeset 043cd60 by Serhiy Storchaka in branch 'main':
bpo-44806: Fix __init__ in subclasses of protocols (GH-27545)
043cd60

[ambv]

New changeset 0f6a773 by Miss Islington (bot) in branch '3.9':
bpo-44806: Fix __init__ in subclasses of protocols (GH-27545) (GH-27559)
0f6a773

[miss-islington]

New changeset 2cc19a5 by Miss Islington (bot) in branch '3.10':
bpo-44806: Fix __init__ in subclasses of protocols (GH-27545)
2cc19a5