Introduce NothingType

src/attr/__init__.py

@@ -5,7 +5,7 @@
 """
 
 from functools import partial
-from typing import Callable, Protocol
+from typing import Callable, Literal, Protocol
 
 from . import converters, exceptions, filters, setters, validators
 from ._cmp import cmp_using
@@ -16,6 +16,7 @@
     Attribute,
     Converter,
     Factory,
+    _Nothing,
     attrib,
     attrs,
     fields,
@@ -36,12 +37,15 @@ class AttrsInstance(Protocol):
     pass
 
 
+NothingType = Literal[_Nothing.NOTHING]
+
 __all__ = [
     "Attribute",
     "AttrsInstance",
     "Converter",
     "Factory",
     "NOTHING",
+    "NothingType",
     "asdict",
     "assoc",
     "astuple",

src/attr/__init__.pyi

@@ -5,6 +5,7 @@ from typing import (
     Any,
     Callable,
     Generic,
+    Literal,
     Mapping,
     Protocol,
     Sequence,
@@ -37,9 +38,9 @@ from attrs import (
 )
 
 if sys.version_info >= (3, 10):
-    from typing import TypeGuard
+    from typing import TypeGuard, TypeAlias
 else:
-    from typing_extensions import TypeGuard
+    from typing_extensions import TypeGuard, TypeAlias
 
 if sys.version_info >= (3, 11):
     from typing import dataclass_transform
@@ -72,11 +73,11 @@ class _Nothing(enum.Enum):
     NOTHING = enum.auto()
 
 NOTHING = _Nothing.NOTHING
+NothingType: TypeAlias = Literal[_Nothing.NOTHING]
 
 # NOTE: Factory lies about its return type to make this possible:
 # `x: List[int] # = Factory(list)`
 # Work around mypy issue #4554 in the common case by using an overload.
-from typing import Literal
 
 @overload
 def Factory(factory: Callable[[], _T]) -> _T: ...

src/attrs/__init__.py

@@ -6,6 +6,7 @@
     AttrsInstance,
     Converter,
     Factory,
+    NothingType,
     _make_getattr,
     assoc,
     cmp_using,
@@ -58,6 +59,7 @@
     "make_class",
     "mutable",
     "NOTHING",
+    "NothingType",
     "resolve_types",
     "setters",
     "validate",