[Python-checkins] bpo-44353: Refactor typing.NewType into callable class (GH-27250)

[ambv]

https://github.com/python/cpython/commit/965dd76e9060e27e2253ba8c8d21a142b178720d
commit: 965dd76e9060e27e2253ba8c8d21a142b178720d
branch: main
author: Yurii Karabas <1998uriyyo at gmail.com>
committer: ambv <lukasz at langa.pl>
date: 2021-07-20T15:20:38+02:00
summary:

bpo-44353: Refactor typing.NewType into callable class (GH-27250)

files:
A Misc/NEWS.d/next/Library/2021-07-19-22-43-15.bpo-44353.HF81_Q.rst
M Lib/test/test_typing.py
M Lib/typing.py

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index b696447d0982b..169b92b651379 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -3691,6 +3691,26 @@ 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):
diff --git a/Lib/typing.py b/Lib/typing.py
index 4a6efee802042..1aff0a1b3026d 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -1374,6 +1374,12 @@ 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.
@@ -2350,7 +2356,7 @@ 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
@@ -2369,12 +2375,23 @@ 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)
diff --git a/Misc/NEWS.d/next/Library/2021-07-19-22-43-15.bpo-44353.HF81_Q.rst b/Misc/NEWS.d/next/Library/2021-07-19-22-43-15.bpo-44353.HF81_Q.rst
new file mode 100644
index 0000000000000..8a1e0f77b3177
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-07-19-22-43-15.bpo-44353.HF81_Q.rst
@@ -0,0 +1,2 @@
+Refactor ``typing.NewType`` from function into callable class. Patch
+provided by Yurii Karabas.