Empty typing.NamedTuple creation is not tested

[sobolevn]

BPO	45280
Nosy	@ambv, @miss-islington, @sobolevn
PRs	bpo-45280: Add test for empty NamedTuple in test_typing #28559 [3.9] bpo-45280: Add test for empty NamedTuple in test_typing (GH-28559) #28570 [3.10] bpo-45280: Add test for empty NamedTuple in test_typing (GH-28559) #28571

^{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 2021-09-26.17:10:10.836>
created_at = <Date 2021-09-24.11:23:41.528>
labels = ['type-bug', 'tests', '3.9', '3.10', '3.11']
title = 'Empty typing.NamedTuple creation is not tested'
updated_at = <Date 2021-09-26.17:10:10.835>
user = 'https://github.com/sobolevn'

bugs.python.org fields:

activity = <Date 2021-09-26.17:10:10.835>
actor = 'lukasz.langa'
assignee = 'none'
closed = True
closed_date = <Date 2021-09-26.17:10:10.836>
closer = 'lukasz.langa'
components = ['Tests']
creation = <Date 2021-09-24.11:23:41.528>
creator = 'sobolevn'
dependencies = []
files = []
hgrepos = []
issue_num = 45280
keywords = ['patch']
message_count = 5.0
messages = ['402557', '402669', '402672', '402673', '402674']
nosy_count = 3.0
nosy_names = ['lukasz.langa', 'miss-islington', 'sobolevn']
pr_nums = ['28559', '28570', '28571']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45280'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[sobolevn]

While working on mypy support of NamedTuples (python/mypy#11047), I've noticed that currently when testing typing.NamedTuple cases like:

1. N = NamedTuple('N')

and

class N(NamedTuple):
    ...

are ignored.

However, this is an important corner-cases, we need to be sure that use can create empty named tuples if needed.

Related position in code:

cpython/Lib/test/test_typing.py

Lines 4102 to 4114 in 3f8b23f

	def test_namedtuple_errors(self):
	with self.assertRaises(TypeError):
	NamedTuple.__new__()
	with self.assertRaises(TypeError):
	NamedTuple()
	with self.assertRaises(TypeError):
	NamedTuple('Emp', [('name', str)], None)
	with self.assertRaises(ValueError):
	NamedTuple('Emp', [('_name', str)])
	with self.assertRaises(TypeError):
	NamedTuple(typename='Emp', name=str, id=int)
	with self.assertRaises(TypeError):
	NamedTuple('Emp', fields=[('name', str), ('id', int)])

I will send a PR add these two cases.

[ambv]

New changeset f56268a by Nikita Sobolev in branch 'main':
bpo-45280: Add test for empty NamedTuple in test_typing (GH-28559)
f56268a

[ambv]

New changeset 08e387a by Miss Islington (bot) in branch '3.9':
bpo-45280: Add test for empty NamedTuple in test_typing (GH-28559) (GH-28570)
08e387a

[ambv]

New changeset d452b29 by Miss Islington (bot) in branch '3.10':
bpo-45280: Add test for empty NamedTuple in test_typing (GH-28559) (GH-28571)
d452b29

[ambv]

Thanks, Nikita! ✨ 🍰 ✨