Fix Literal bug with typing-extension==4.6.0 (#5826)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Samuel Colvin <s@muelcolvin.com>

changes/5826-hramezani.md

@@ -0,0 +1 @@
+Fix a bug in `Literal` usage with `typing-extension==4.6.0`

pydantic/typing.py

@@ -1,4 +1,5 @@
 import sys
+import typing
 from collections.abc import Callable
 from os import PathLike
 from typing import (  # type: ignore
@@ -91,6 +92,11 @@ def get_all_type_hints(obj: Any, globalns: Any = None, localns: Any = None) -> A
 AnnotatedTypeNames = {'AnnotatedMeta', '_AnnotatedAlias'}
 
 
+LITERAL_TYPES: Set[Any] = {Literal}
+if hasattr(typing, 'Literal'):
+    LITERAL_TYPES.add(typing.Literal)
+
+
 if sys.version_info < (3, 8):
 
     def get_origin(t: Type[Any]) -> Optional[Type[Any]]:
@@ -354,10 +360,7 @@ def is_none_type(type_: Any) -> bool:
 else:
 
     def is_none_type(type_: Any) -> bool:
-        for none_type in NONE_TYPES:
-            if type_ is none_type:
-                return True
-        return False
+        return type_ in NONE_TYPES
 
 
 def display_as_type(v: Type[Any]) -> str:
@@ -415,7 +418,7 @@ def is_callable_type(type_: Type[Any]) -> bool:
 
 
 def is_literal_type(type_: Type[Any]) -> bool:
-    return Literal is not None and get_origin(type_) is Literal
+    return Literal is not None and get_origin(type_) in LITERAL_TYPES
 
 
 def literal_values(type_: Type[Any]) -> Tuple[Any, ...]:

tests/requirements-testing.txt

@@ -8,7 +8,7 @@ pytest-cov==4.0.0
 pytest-mock==3.10.0
 pytest-sugar==0.9.6
 # pin typing-extensions to minimum requirement - see #4885
-typing-extensions==4.2.0
+typing-extensions==4.6.0
 # used in FastAPI tests, pin to avoid warnings in newer version
 # that FastAPI needs to fix
 Flask==2.2.3

tests/test_types.py

@@ -3440,3 +3440,22 @@ class Model(BaseModel):
             'type': 'value_error.date.not_in_the_future',
         }
     ]
+
+
+def test_typing_extension_literal_field():
+    from typing_extensions import Literal
+
+    class Model(BaseModel):
+        foo: Literal['foo']
+
+    assert Model(foo='foo').foo == 'foo'
+
+
+@pytest.mark.skipif(sys.version_info < (3, 8), reason='`typing.Literal` is available for python 3.8 and above.')
+def test_typing_literal_field():
+    from typing import Literal
+
+    class Model(BaseModel):
+        foo: Literal['foo']
+
+    assert Model(foo='foo').foo == 'foo'

tests/test_typing.py

@@ -6,7 +6,7 @@
 from typing_extensions import Annotated  # noqa: F401
 
 from pydantic import Field  # noqa: F401
-from pydantic.typing import Literal, convert_generics, is_namedtuple, is_none_type, is_typeddict
+from pydantic.typing import Literal, convert_generics, is_literal_type, is_namedtuple, is_none_type, is_typeddict
 
 try:
     from typing import TypedDict as typing_TypedDict
@@ -124,3 +124,18 @@ def test_convert_generics_pep604():
     assert (
         convert_generics(dict['Hero', list['Team']] | int) == dict[ForwardRef('Hero'), list[ForwardRef('Team')]] | int
     )
+
+
+def test_is_literal_with_typing_extension_literal():
+    from typing_extensions import Literal
+
+    assert is_literal_type(Literal) is False
+    assert is_literal_type(Literal['foo']) is True
+
+
+@pytest.mark.skipif(sys.version_info < (3, 8), reason='`typing.Literal` is available for python 3.8 and above.')
+def test_is_literal_with_typing_literal():
+    from typing import Literal
+
+    assert is_literal_type(Literal) is False
+    assert is_literal_type(Literal['foo']) is True