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gh-105570: Deprecate unusual ways of creating empty TypedDicts (#105780)

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Deprecate two methods of creating typing.TypedDict classes with 0 fields using the functional syntax: `TD = TypedDict("TD")` and `TD = TypedDict("TD", None)`. Both will be disallowed in Python 3.15. To create a TypedDict class with 0 fields, either use `class TD(TypedDict): pass` or `TD = TypedDict("TD", {})`.
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Alex Waygood 2023-06-14 15:58:41 +01:00 • committed by GitHub
parent d32e8d6070
commit 7b1f0f204a
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5 changed files with 73 additions and 8 deletions
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34
Lib/test/test_typing.py
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@ -7823,6 +7823,40 @@ class TypedDictTests(BaseTestCase):
self.assertEqual(MultipleGenericBases.__orig_bases__, (GenericParent[int], GenericParent[float]))
self.assertEqual(CallTypedDict.__orig_bases__, (TypedDict,))
def test_zero_fields_typeddicts(self):
T1 = TypedDict("T1", {})
class T2(TypedDict): pass
class T3[tvar](TypedDict): pass
S = TypeVar("S")
class T4(TypedDict, Generic[S]): pass
expected_warning = re.escape(
"Failing to pass a value for the 'fields' parameter is deprecated "
"and will be disallowed in Python 3.15. "
"To create a TypedDict class with 0 fields "
"using the functional syntax, "
"pass an empty dictionary, e.g. `T5 = TypedDict('T5', {})`."
)
with self.assertWarnsRegex(DeprecationWarning, fr"^{expected_warning}$"):
T5 = TypedDict('T5')
expected_warning = re.escape(
"Passing `None` as the 'fields' parameter is deprecated "
"and will be disallowed in Python 3.15. "
"To create a TypedDict class with 0 fields "
"using the functional syntax, "
"pass an empty dictionary, e.g. `T6 = TypedDict('T6', {})`."
)
with self.assertWarnsRegex(DeprecationWarning, fr"^{expected_warning}$"):
T6 = TypedDict('T6', None)
for klass in T1, T2, T3, T4, T5, T6:
with self.subTest(klass=klass.__name__):
self.assertEqual(klass.__annotations__, {})
self.assertEqual(klass.__required_keys__, set())
self.assertEqual(klass.__optional_keys__, set())
self.assertIsInstance(klass(), dict)
class RequiredTests(BaseTestCase):