dataclasses: various fixes (#4937)

stdlib/3.7/dataclasses.pyi

@@ -17,14 +17,27 @@ def asdict(obj: Any, *, dict_factory: Callable[[List[Tuple[str, Any]]], _T]) ->
 def astuple(obj: Any) -> Tuple[Any, ...]: ...
 @overload
 def astuple(obj: Any, *, tuple_factory: Callable[[List[Any]], _T]) -> _T: ...
-@overload
-def dataclass(_cls: Type[_T]) -> Type[_T]: ...
-@overload
-def dataclass(_cls: None) -> Callable[[Type[_T]], Type[_T]]: ...
-@overload
-def dataclass(
-    *, init: bool = ..., repr: bool = ..., eq: bool = ..., order: bool = ..., unsafe_hash: bool = ..., frozen: bool = ...
-) -> Callable[[Type[_T]], Type[_T]]: ...
+
+if sys.version_info >= (3, 8):
+    # cls argument is now positional-only
+    @overload
+    def dataclass(__cls: Type[_T]) -> Type[_T]: ...
+    @overload
+    def dataclass(__cls: None) -> Callable[[Type[_T]], Type[_T]]: ...
+    @overload
+    def dataclass(
+        *, init: bool = ..., repr: bool = ..., eq: bool = ..., order: bool = ..., unsafe_hash: bool = ..., frozen: bool = ...
+    ) -> Callable[[Type[_T]], Type[_T]]: ...
+
+else:
+    @overload
+    def dataclass(_cls: Type[_T]) -> Type[_T]: ...
+    @overload
+    def dataclass(_cls: None) -> Callable[[Type[_T]], Type[_T]]: ...
+    @overload
+    def dataclass(
+        *, init: bool = ..., repr: bool = ..., eq: bool = ..., order: bool = ..., unsafe_hash: bool = ..., frozen: bool = ...
+    ) -> Callable[[Type[_T]], Type[_T]]: ...
 
 class Field(Generic[_T]):
     name: str
@@ -36,6 +49,16 @@ class Field(Generic[_T]):
     init: bool
     compare: bool
     metadata: Mapping[str, Any]
+    def __init__(
+        self,
+        default: _T,
+        default_factory: Callable[[], _T],
+        init: bool,
+        repr: bool,
+        hash: Optional[bool],
+        compare: bool,
+        metadata: Mapping[str, Any],
+    ) -> None: ...
     if sys.version_info >= (3, 9):
         def __class_getitem__(cls, item: Any) -> GenericAlias: ...
 
@@ -76,8 +99,13 @@ def is_dataclass(obj: Any) -> bool: ...
 class FrozenInstanceError(AttributeError): ...
 
 class InitVar(Generic[_T]):
+    type: Type[_T]
+    def __init__(self, type: Type[_T]) -> None: ...
     if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, type: Any) -> GenericAlias: ...
+        @overload
+        def __class_getitem__(cls, type: Type[_T]) -> InitVar[_T]: ...
+        @overload
+        def __class_getitem__(cls, type: Any) -> InitVar[Any]: ...
 
 def make_dataclass(
     cls_name: str,
@@ -92,4 +120,4 @@ def make_dataclass(
     unsafe_hash: bool = ...,
     frozen: bool = ...,
 ) -> type: ...
-def replace(obj: _T, **changes: Any) -> _T: ...
+def replace(__obj: _T, **changes: Any) -> _T: ...

tests/stubtest_whitelists/py39.txt

@@ -37,6 +37,7 @@ copy.PyStringMap
 dataclasses.Field.__init__
 dataclasses.InitVar.__init__
 dataclasses.field
+dataclasses.InitVar.__class_getitem__  # stubtest bug. doesn't do the right thing with overload + implicit classmethod __class_getitem__
 dummy_threading
 email.message.MIMEPart.as_string
 enum.Enum._generate_next_value_