Update attrs and use attrs.NothingType (#622)

pyproject.toml

@@ -11,7 +11,6 @@ test = [
     "pytest>=8.3.2",
     "pytest-benchmark>=4.0.0",
     "immutables>=0.20",
-    "typing-extensions>=4.7.1",
     "coverage>=7.6.1",
     "pytest-xdist>=3.6.1",
 ]
@@ -22,7 +21,6 @@ docs = [
     "myst-parser>=1.0.0",
     "pendulum>=2.1.2",
     "sphinx-autobuild",
-    "typing-extensions>=4.8.0",
 ]
 bench = [
     "pyperf>=2.6.1",
@@ -42,7 +40,7 @@ authors = [
     {name = "Tin Tvrtkovic", email = "tinchester@gmail.com"},
 ]
 dependencies = [
-    "attrs>=23.1.0",
+    "attrs>=24.3.0",
     "typing-extensions>=4.12.2",
     "exceptiongroup>=1.1.1; python_version < '3.11'",
 ]

src/cattrs/_compat.py

@@ -42,7 +42,7 @@
 from typing import Sequence as TypingSequence
 from typing import Set as TypingSet
 
-from attrs import NOTHING, Attribute, Factory, resolve_types
+from attrs import NOTHING, Attribute, Factory, NothingType, resolve_types
 from attrs import fields as attrs_fields
 from attrs import fields_dict as attrs_fields_dict
 
@@ -296,7 +296,7 @@ def get_newtype_base(typ: Any) -> Optional[type]:
         return None
 
 
-def get_notrequired_base(type) -> "Union[Any, Literal[NOTHING]]":
+def get_notrequired_base(type) -> Union[Any, NothingType]:
     if is_annotated(type):
         # Handle `Annotated[NotRequired[int]]`
         type = get_args(type)[0]

src/cattrs/cols.py

@@ -3,7 +3,7 @@
 from __future__ import annotations
 
 from collections import defaultdict
-from collections.abc import Iterable
+from collections.abc import Callable, Iterable
 from functools import partial
 from typing import (
     TYPE_CHECKING,
@@ -15,7 +15,7 @@
     get_type_hints,
 )
 
-from attrs import NOTHING, Attribute
+from attrs import NOTHING, Attribute, NothingType
 
 from ._compat import (
     ANIES,
@@ -294,7 +294,9 @@ def is_defaultdict(type: Any) -> bool:
 
 
 def defaultdict_structure_factory(
-    type: type[defaultdict], converter: BaseConverter, default_factory: Any = NOTHING
+    type: type[defaultdict],
+    converter: BaseConverter,
+    default_factory: Callable[[], Any] | NothingType = NOTHING,
 ) -> StructureHook:
     """A structure hook factory for defaultdicts.
 

src/cattrs/strategies/_unions.py

@@ -1,7 +1,7 @@
 from collections import defaultdict
-from typing import Any, Callable, Literal, Union
+from typing import Any, Callable, Union
 
-from attrs import NOTHING
+from attrs import NOTHING, NothingType
 
 from cattrs import BaseConverter
 from cattrs._compat import get_newtype_base, is_literal, is_subclass, is_union_type
@@ -23,7 +23,7 @@ def configure_tagged_union(
     converter: BaseConverter,
     tag_generator: Callable[[type], str] = default_tag_generator,
     tag_name: str = "_type",
-    default: Union[type, Literal[NOTHING]] = NOTHING,
+    default: Union[type, NothingType] = NOTHING,
 ) -> None:
     """
     Configure the converter so that `union` (which should be a union) is