Nested subclasses of typing.NamedTuple are not pickleable

[serhiy-storchaka]

BPO	38405
Nosy	@gvanrossum, @serhiy-storchaka, @ilevkivskyi, @miss-islington
PRs	bpo-38405: Make nested subclasses of typing.NamedTuple pickleable. #16641 [3.8] bpo-38405: Make nested subclasses of typing.NamedTuple pickleable. (GH-16641) #16655 [3.7] bpo-38405: Make nested subclasses of typing.NamedTuple pickleable. (GH-16641). #16674

^{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 2019-10-09.09:58:47.335>
created_at = <Date 2019-10-08.08:18:02.328>
labels = ['3.7', '3.8', 'type-bug', 'library', '3.9']
title = 'Nested subclasses of typing.NamedTuple are not pickleable'
updated_at = <Date 2019-10-09.09:58:47.335>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2019-10-09.09:58:47.335>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2019-10-09.09:58:47.335>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2019-10-08.08:18:02.328>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 38405
keywords = ['patch']
message_count = 4.0
messages = ['354176', '354203', '354211', '354260']
nosy_count = 4.0
nosy_names = ['gvanrossum', 'serhiy.storchaka', 'levkivskyi', 'miss-islington']
pr_nums = ['16641', '16655', '16674']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue38405'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']

[serhiy-storchaka]

Example:

>>> from typing import NamedTuple
>>> import pickle
>>> class A:
...     class B(NamedTuple):
...         x: int
... 
>>> pickle.dumps(A.B)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
_pickle.PicklingError: Can't pickle <class '__main__.B'>: attribute lookup B on __main__ failed

[serhiy-storchaka]

New changeset 13abda4 by Serhiy Storchaka in branch 'master':
bpo-38405: Make nested subclasses of typing.NamedTuple pickleable. (GH-16641)
13abda4

[miss-islington]

New changeset 10b475a by Miss Islington (bot) in branch '3.8':
bpo-38405: Make nested subclasses of typing.NamedTuple pickleable. (GH-16641)
10b475a

[serhiy-storchaka]

New changeset 87db4d3 by Serhiy Storchaka in branch '3.7':
[3.7] bpo-38405: Make nested subclasses of typing.NamedTuple pickleable. (GH-16641). (GH-16674)
87db4d3