bpo-40389: Improve repr of typing.Optional (#19714)
diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py
index e8fe455..b20103b 100644
--- a/Lib/test/test_dataclasses.py
+++ b/Lib/test/test_dataclasses.py
@@ -2028,7 +2028,7 @@
class C:
x: Union[int, type(None)] = None
- self.assertDocStrEqual(C.__doc__, "C(x:Union[int, NoneType]=None)")
+ self.assertDocStrEqual(C.__doc__, "C(x:Optional[int]=None)")
def test_docstring_list_field(self):
@dataclass
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index cab8de0..21bc7c8 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -1750,7 +1750,7 @@
self.assertEqual(repr(Union[Tuple, Tuple[int]]).replace('typing.', ''),
'Union[Tuple, Tuple[int]]')
self.assertEqual(repr(Callable[..., Optional[T]][int]).replace('typing.', ''),
- 'Callable[..., Union[int, NoneType]]')
+ 'Callable[..., Optional[int]]')
self.assertEqual(repr(Callable[[], List[T]][int]).replace('typing.', ''),
'Callable[[], List[int]]')
diff --git a/Lib/typing.py b/Lib/typing.py
index c829898..f3cd280 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -691,6 +691,13 @@
return _GenericAlias(self.__origin__, params, name=self._name, inst=self._inst)
def __repr__(self):
+ if (self.__origin__ == Union and len(self.__args__) == 2
+ and type(None) in self.__args__):
+ if self.__args__[0] is not type(None):
+ arg = self.__args__[0]
+ else:
+ arg = self.__args__[1]
+ return (f'typing.Optional[{_type_repr(arg)}]')
if (self._name != 'Callable' or
len(self.__args__) == 2 and self.__args__[0] is Ellipsis):
if self._name: