gh-105499: Merge typing.Union and types.UnionType (#105511)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Ken Jin <kenjin@python.org>
Co-authored-by: Carl Meyer <carl@oddbird.net>

1 files changed, 58 insertions, 38 deletions

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 591fb860eee..e88c811bfca 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -502,7 +502,7 @@ class TypeVarTests(BaseTestCase):
 
     def test_bound_errors(self):
         with self.assertRaises(TypeError):
-            TypeVar('X', bound=Union)
+            TypeVar('X', bound=Optional)
         with self.assertRaises(TypeError):
             TypeVar('X', str, float, bound=Employee)
         with self.assertRaisesRegex(TypeError,
@@ -542,7 +542,7 @@ class TypeVarTests(BaseTestCase):
     def test_bad_var_substitution(self):
         T = TypeVar('T')
         bad_args = (
-            (), (int, str), Union,
+            (), (int, str), Optional,
             Generic, Generic[T], Protocol, Protocol[T],
             Final, Final[int], ClassVar, ClassVar[int],
         )
@@ -2044,10 +2044,6 @@ class UnionTests(BaseTestCase):
 
     def test_union_issubclass_type_error(self):
         with self.assertRaises(TypeError):
-            issubclass(int, Union)
-        with self.assertRaises(TypeError):
-            issubclass(Union, int)
-        with self.assertRaises(TypeError):
             issubclass(Union[int, str], int)
         with self.assertRaises(TypeError):
             issubclass(int, Union[str, list[int]])
@@ -2121,41 +2117,40 @@ class UnionTests(BaseTestCase):
 
         self.assertEqual(Union[A, B].__args__, (A, B))
         union1 = Union[A, B]
-        with self.assertRaises(TypeError):
+        with self.assertRaisesRegex(TypeError, "unhashable type: 'UnhashableMeta'"):
             hash(union1)
 
         union2 = Union[int, B]
-        with self.assertRaises(TypeError):
+        with self.assertRaisesRegex(TypeError, "unhashable type: 'UnhashableMeta'"):
             hash(union2)
 
         union3 = Union[A, int]
-        with self.assertRaises(TypeError):
+        with self.assertRaisesRegex(TypeError, "unhashable type: 'UnhashableMeta'"):
             hash(union3)
 
     def test_repr(self):
-        self.assertEqual(repr(Union), 'typing.Union')
         u = Union[Employee, int]
-        self.assertEqual(repr(u), 'typing.Union[%s.Employee, int]' % __name__)
+        self.assertEqual(repr(u), f'{__name__}.Employee | int')
         u = Union[int, Employee]
-        self.assertEqual(repr(u), 'typing.Union[int, %s.Employee]' % __name__)
+        self.assertEqual(repr(u), f'int | {__name__}.Employee')
         T = TypeVar('T')
         u = Union[T, int][int]
         self.assertEqual(repr(u), repr(int))
         u = Union[List[int], int]
-        self.assertEqual(repr(u), 'typing.Union[typing.List[int], int]')
+        self.assertEqual(repr(u), 'typing.List[int] | int')
         u = Union[list[int], dict[str, float]]
-        self.assertEqual(repr(u), 'typing.Union[list[int], dict[str, float]]')
+        self.assertEqual(repr(u), 'list[int] | dict[str, float]')
         u = Union[int | float]
-        self.assertEqual(repr(u), 'typing.Union[int, float]')
+        self.assertEqual(repr(u), 'int | float')
 
         u = Union[None, str]
-        self.assertEqual(repr(u), 'typing.Optional[str]')
+        self.assertEqual(repr(u), 'None | str')
         u = Union[str, None]
-        self.assertEqual(repr(u), 'typing.Optional[str]')
+        self.assertEqual(repr(u), 'str | None')
         u = Union[None, str, int]
-        self.assertEqual(repr(u), 'typing.Union[NoneType, str, int]')
+        self.assertEqual(repr(u), 'None | str | int')
         u = Optional[str]
-        self.assertEqual(repr(u), 'typing.Optional[str]')
+        self.assertEqual(repr(u), 'str | None')
 
     def test_dir(self):
         dir_items = set(dir(Union[str, int]))
@@ -2167,14 +2162,11 @@ class UnionTests(BaseTestCase):
 
     def test_cannot_subclass(self):
         with self.assertRaisesRegex(TypeError,
-                r'Cannot subclass typing\.Union'):
+                r"type 'typing\.Union' is not an acceptable base type"):
             class C(Union):
                 pass
-        with self.assertRaisesRegex(TypeError, CANNOT_SUBCLASS_TYPE):
-            class D(type(Union)):
-                pass
         with self.assertRaisesRegex(TypeError,
-                r'Cannot subclass typing\.Union\[int, str\]'):
+                r'Cannot subclass int \| str'):
             class E(Union[int, str]):
                 pass
 
@@ -2220,7 +2212,7 @@ class UnionTests(BaseTestCase):
 
     def test_function_repr_union(self):
         def fun() -> int: ...
-        self.assertEqual(repr(Union[fun, int]), 'typing.Union[fun, int]')
+        self.assertEqual(repr(Union[fun, int]), f'{__name__}.{fun.__qualname__} | int')
 
     def test_union_str_pattern(self):
         # Shouldn't crash; see http://bugs.python.org/issue25390
@@ -4895,11 +4887,11 @@ class GenericTests(BaseTestCase):
     def test_extended_generic_rules_repr(self):
         T = TypeVar('T')
         self.assertEqual(repr(Union[Tuple, Callable]).replace('typing.', ''),
-                         'Union[Tuple, Callable]')
+                         'Tuple | Callable')
         self.assertEqual(repr(Union[Tuple, Tuple[int]]).replace('typing.', ''),
-                         'Union[Tuple, Tuple[int]]')
+                         'Tuple | Tuple[int]')
         self.assertEqual(repr(Callable[..., Optional[T]][int]).replace('typing.', ''),
-                         'Callable[..., Optional[int]]')
+                         'Callable[..., int | None]')
         self.assertEqual(repr(Callable[[], List[T]][int]).replace('typing.', ''),
                          'Callable[[], List[int]]')
 
@@ -5079,9 +5071,9 @@ class GenericTests(BaseTestCase):
         with self.assertRaises(TypeError):
             issubclass(Tuple[int, ...], typing.Iterable)
 
-    def test_fail_with_bare_union(self):
+    def test_fail_with_special_forms(self):
         with self.assertRaises(TypeError):
-            List[Union]
+            List[Final]
         with self.assertRaises(TypeError):
             Tuple[Optional]
         with self.assertRaises(TypeError):
@@ -5623,8 +5615,6 @@ class GenericTests(BaseTestCase):
         for obj in (
             ClassVar[int],
             Final[int],
-            Union[int, float],
-            Optional[int],
             Literal[1, 2],
             Concatenate[int, ParamSpec("P")],
             TypeGuard[int],
@@ -5656,7 +5646,7 @@ class GenericTests(BaseTestCase):
             __parameters__ = (T,)
         # Bare classes should be skipped
         for a in (List, list):
-            for b in (A, int, TypeVar, TypeVarTuple, ParamSpec, types.GenericAlias, types.UnionType):
+            for b in (A, int, TypeVar, TypeVarTuple, ParamSpec, types.GenericAlias, Union):
                 with self.subTest(generic=a, sub=b):
                     with self.assertRaisesRegex(TypeError, '.* is not a generic class'):
                         a[b][str]
@@ -5675,7 +5665,7 @@ class GenericTests(BaseTestCase):
 
         for s in (int, G, A, List, list,
                   TypeVar, TypeVarTuple, ParamSpec,
-                  types.GenericAlias, types.UnionType):
+                  types.GenericAlias, Union):
 
             for t in Tuple, tuple:
                 with self.subTest(tuple=t, sub=s):
@@ -7176,7 +7166,7 @@ class GetUtilitiesTestCase(TestCase):
         self.assertIs(get_origin(Callable), collections.abc.Callable)
         self.assertIs(get_origin(list[int]), list)
         self.assertIs(get_origin(list), None)
-        self.assertIs(get_origin(list | str), types.UnionType)
+        self.assertIs(get_origin(list | str), Union)
         self.assertIs(get_origin(P.args), P)
         self.assertIs(get_origin(P.kwargs), P)
         self.assertIs(get_origin(Required[int]), Required)
@@ -10434,7 +10424,6 @@ class SpecialAttrsTests(BaseTestCase):
             typing.TypeGuard: 'TypeGuard',
             typing.TypeIs: 'TypeIs',
             typing.TypeVar: 'TypeVar',
-            typing.Union: 'Union',
             typing.Self: 'Self',
             # Subscripted special forms
             typing.Annotated[Any, "Annotation"]: 'Annotated',
@@ -10445,7 +10434,7 @@ class SpecialAttrsTests(BaseTestCase):
             typing.Literal[Any]: 'Literal',
             typing.Literal[1, 2]: 'Literal',
             typing.Literal[True, 2]: 'Literal',
-            typing.Optional[Any]: 'Optional',
+            typing.Optional[Any]: 'Union',
             typing.TypeGuard[Any]: 'TypeGuard',
             typing.TypeIs[Any]: 'TypeIs',
             typing.Union[Any]: 'Any',
@@ -10464,7 +10453,10 @@ class SpecialAttrsTests(BaseTestCase):
                 for proto in range(pickle.HIGHEST_PROTOCOL + 1):
                     s = pickle.dumps(cls, proto)
                     loaded = pickle.loads(s)
-                    self.assertIs(cls, loaded)
+                    if isinstance(cls, Union):
+                        self.assertEqual(cls, loaded)
+                    else:
+                        self.assertIs(cls, loaded)
 
     TypeName = typing.NewType('SpecialAttrsTests.TypeName', Any)
 
@@ -10739,6 +10731,34 @@ class TypeIterationTests(BaseTestCase):
             self.assertNotIsInstance(type_to_test, collections.abc.Iterable)
 
 
+class UnionGenericAliasTests(BaseTestCase):
+    def test_constructor(self):
+        # Used e.g. in typer, pydantic
+        with self.assertWarns(DeprecationWarning):
+            inst = typing._UnionGenericAlias(typing.Union, (int, str))
+        self.assertEqual(inst, int | str)
+        with self.assertWarns(DeprecationWarning):
+            # name is accepted but ignored
+            inst = typing._UnionGenericAlias(typing.Union, (int, None), name="Optional")
+        self.assertEqual(inst, int | None)
+
+    def test_isinstance(self):
+        # Used e.g. in pydantic
+        with self.assertWarns(DeprecationWarning):
+            self.assertTrue(isinstance(Union[int, str], typing._UnionGenericAlias))
+        with self.assertWarns(DeprecationWarning):
+            self.assertFalse(isinstance(int, typing._UnionGenericAlias))
+
+    def test_eq(self):
+        # type(t) == _UnionGenericAlias is used in vyos
+        with self.assertWarns(DeprecationWarning):
+            self.assertEqual(Union, typing._UnionGenericAlias)
+        with self.assertWarns(DeprecationWarning):
+            self.assertEqual(typing._UnionGenericAlias, typing._UnionGenericAlias)
+        with self.assertWarns(DeprecationWarning):
+            self.assertNotEqual(int, typing._UnionGenericAlias)
+
+
 def load_tests(loader, tests, pattern):
     import doctest
     tests.addTests(doctest.DocTestSuite(typing))