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[3.10] bpo-44353: Refactor typing.NewType into callable class (GH-27250) #27258

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Merged
ambv merged 1 commit into from
Jul 20, 2021
Merged

[3.10] bpo-44353: Refactor typing.NewType into callable class (GH-27250) #27258

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20 changes: 20 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3690,6 +3690,26 @@ def test_errors(self):
class D(UserName):
pass

def test_or(self):
UserId = NewType('UserId', int)

self.assertEqual(UserId | int, Union[UserId, int])
self.assertEqual(int | UserId, Union[int, UserId])

self.assertEqual(get_args(UserId | int), (UserId, int))
self.assertEqual(get_args(int | UserId), (int, UserId))

def test_special_attrs(self):
UserId = NewType('UserId', int)

self.assertEqual(UserId.__name__, 'UserId')
self.assertEqual(UserId.__qualname__, 'UserId')
self.assertEqual(UserId.__module__, __name__)

def test_repr(self):
UserId = NewType('UserId', int)

self.assertEqual(repr(UserId), f'{__name__}.UserId')

class NamedTupleTests(BaseTestCase):
class NestedEmployee(NamedTuple):
Expand Down
27 changes: 22 additions & 5 deletions Lib/typing.py
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Expand Up @@ -1373,6 +1373,12 @@ def _no_init(self, *args, **kwargs):
if type(self)._is_protocol:
raise TypeError('Protocols cannot be instantiated')

def _callee(depth=2, default=None):
try:
return sys._getframe(depth).f_globals['__name__']
except (AttributeError, ValueError): # For platforms without _getframe()
return default


def _allow_reckless_class_checks(depth=3):
"""Allow instance and class checks for special stdlib modules.
Expand Down Expand Up @@ -2349,7 +2355,7 @@ class body be required.
TypedDict.__mro_entries__ = lambda bases: (_TypedDict,)


def NewType(name, tp):
class NewType:
"""NewType creates simple unique types with almost zero
runtime overhead. NewType(name, tp) is considered a subtype of tp
by static type checkers. At runtime, NewType(name, tp) returns
Expand All @@ -2368,12 +2374,23 @@ def name_by_id(user_id: UserId) -> str:
num = UserId(5) + 1 # type: int
"""

def new_type(x):
def __init__(self, name, tp):
self.__name__ = name
self.__qualname__ = name
self.__module__ = _callee(default='typing')
self.__supertype__ = tp

def __repr__(self):
return f'{self.__module__}.{self.__qualname__}'

def __call__(self, x):
return x

new_type.__name__ = name
new_type.__supertype__ = tp
return new_type
def __or__(self, other):
return Union[self, other]

def __ror__(self, other):
return Union[other, self]


# Python-version-specific alias (Python 2: unicode; Python 3: str)
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2021-07-19-22-43-15.bpo-44353.HF81_Q.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Refactor ``typing.NewType`` from function into callable class. Patch
provided by Yurii Karabas.