Export DataclassInstance protocol from _typeshed (#9676)

stdlib/_typeshed/__init__.pyi

@@ -8,9 +8,10 @@ import mmap
 import pickle
 import sys
 from collections.abc import Awaitable, Callable, Iterable, Set as AbstractSet
+from dataclasses import Field
 from os import PathLike
 from types import FrameType, TracebackType
-from typing import Any, AnyStr, Generic, Protocol, TypeVar, Union
+from typing import Any, AnyStr, ClassVar, Generic, Protocol, TypeVar, Union
 from typing_extensions import Final, Literal, LiteralString, TypeAlias, final
 
 _KT = TypeVar("_KT")
@@ -304,3 +305,10 @@ ProfileFunction: TypeAlias = Callable[[FrameType, str, Any], object]
 
 # Objects suitable to be passed to sys.settrace, threading.settrace, and similar
 TraceFunction: TypeAlias = Callable[[FrameType, str, Any], TraceFunction | None]
+
+# experimental
+# Might not work as expected for pyright, see
+#   https://github.com/python/typeshed/pull/9362
+#   https://github.com/microsoft/pyright/issues/4339
+class DataclassInstance(Protocol):
+    __dataclass_fields__: ClassVar[dict[str, Field[Any]]]

stdlib/dataclasses.pyi

@@ -1,9 +1,10 @@
 import enum
 import sys
 import types
+from _typeshed import DataclassInstance
 from builtins import type as Type  # alias to avoid name clashes with fields named "type"
 from collections.abc import Callable, Iterable, Mapping
-from typing import Any, ClassVar, Generic, Protocol, TypeVar, overload
+from typing import Any, Generic, Protocol, TypeVar, overload
 from typing_extensions import Literal, TypeAlias, TypeGuard
 
 if sys.version_info >= (3, 9):
@@ -30,10 +31,7 @@ __all__ = [
 if sys.version_info >= (3, 10):
     __all__ += ["KW_ONLY"]
 
-class _DataclassInstance(Protocol):
-    __dataclass_fields__: ClassVar[dict[str, Field[Any]]]
-
-_DataclassT = TypeVar("_DataclassT", bound=_DataclassInstance)
+_DataclassT = TypeVar("_DataclassT", bound=DataclassInstance)
 
 # define _MISSING_TYPE as an enum within the type stubs,
 # even though that is not really its type at runtime
@@ -49,13 +47,13 @@ if sys.version_info >= (3, 10):
     class KW_ONLY: ...
 
 @overload
-def asdict(obj: _DataclassInstance) -> dict[str, Any]: ...
+def asdict(obj: DataclassInstance) -> dict[str, Any]: ...
 @overload
-def asdict(obj: _DataclassInstance, *, dict_factory: Callable[[list[tuple[str, Any]]], _T]) -> _T: ...
+def asdict(obj: DataclassInstance, *, dict_factory: Callable[[list[tuple[str, Any]]], _T]) -> _T: ...
 @overload
-def astuple(obj: _DataclassInstance) -> tuple[Any, ...]: ...
+def astuple(obj: DataclassInstance) -> tuple[Any, ...]: ...
 @overload
-def astuple(obj: _DataclassInstance, *, tuple_factory: Callable[[list[Any]], _T]) -> _T: ...
+def astuple(obj: DataclassInstance, *, tuple_factory: Callable[[list[Any]], _T]) -> _T: ...
 
 if sys.version_info >= (3, 8):
     # cls argument is now positional-only
@@ -223,13 +221,13 @@ else:
         metadata: Mapping[Any, Any] | None = None,
     ) -> Any: ...
 
-def fields(class_or_instance: _DataclassInstance | type[_DataclassInstance]) -> tuple[Field[Any], ...]: ...
+def fields(class_or_instance: DataclassInstance | type[DataclassInstance]) -> tuple[Field[Any], ...]: ...
 @overload
-def is_dataclass(obj: _DataclassInstance | type[_DataclassInstance]) -> Literal[True]: ...
+def is_dataclass(obj: DataclassInstance | type[DataclassInstance]) -> Literal[True]: ...
 @overload
-def is_dataclass(obj: type) -> TypeGuard[type[_DataclassInstance]]: ...
+def is_dataclass(obj: type) -> TypeGuard[type[DataclassInstance]]: ...
 @overload
-def is_dataclass(obj: object) -> TypeGuard[_DataclassInstance | type[_DataclassInstance]]: ...
+def is_dataclass(obj: object) -> TypeGuard[DataclassInstance | type[DataclassInstance]]: ...
 
 class FrozenInstanceError(AttributeError): ...