Fix CloudPathMeta.__call__ return type

cloudpathlib/cloudpath.py

@@ -98,10 +98,12 @@
 implementation_registry: Dict[str, CloudImplementation] = defaultdict(CloudImplementation)
 
 
-def register_path_class(key: str) -> Callable:
-    T = TypeVar("T", bound=Type[CloudPath])
+T = TypeVar("T")
+CloudPathT = TypeVar("CloudPathT", bound="CloudPath")
 
-    def decorator(cls: Type[T]) -> Type[T]:
+
+def register_path_class(key: str) -> Callable[[Type[CloudPathT]], Type[CloudPathT]]:
+    def decorator(cls: Type[CloudPathT]) -> Type[CloudPathT]:
         if not issubclass(cls, CloudPath):
             raise TypeError("Only subclasses of CloudPath can be registered.")
         implementation_registry[key]._path_class = cls
@@ -112,34 +114,47 @@
 
 
 class CloudPathMeta(abc.ABCMeta):
-    def __call__(cls, cloud_path, *args, **kwargs):
+    @overload
+    def __call__(cls: Type[T], cloud_path: CloudPathT, *args: Any, **kwargs: Any) -> CloudPathT:
+        ...
+
+    @overload
+    def __call__(
+        cls: Type[T], cloud_path: Union[str, "CloudPath"], *args: Any, **kwargs: Any
+    ) -> T:
+        ...
+
+    def __call__(
+        cls: Type[T], cloud_path: Union[str, CloudPathT], *args: Any, **kwargs: Any
+    ) -> Union[T, "CloudPath", CloudPathT]:
         # cls is a class that is the instance of this metaclass, e.g., CloudPath
+        if not issubclass(cls, CloudPath):
+            raise TypeError(
+                f"Only subclasses of {CloudPath.__name__} can be instantiated from its meta class."
+            )
 
         # Dispatch to subclass if base CloudPath
-        if cls == CloudPath:
+        if cls is CloudPath:
             for implementation in implementation_registry.values():
                 path_class = implementation._path_class
                 if path_class is not None and path_class.is_valid_cloudpath(
                     cloud_path, raise_on_error=False
                 ):
                     # Instantiate path_class instance
-                    new_obj = path_class.__new__(path_class, cloud_path, *args, **kwargs)
-                    if isinstance(new_obj, path_class):
-                        path_class.__init__(new_obj, cloud_path, *args, **kwargs)
+                    new_obj = object.__new__(path_class)
+                    path_class.__init__(new_obj, cloud_path, *args, **kwargs)  # type: ignore[type-var]
                     return new_obj
-            valid = [
+            valid_prefixes = [
                 impl._path_class.cloud_prefix
                 for impl in implementation_registry.values()
                 if impl._path_class is not None
             ]
             raise InvalidPrefixError(
-                f"Path {cloud_path} does not begin with a known prefix {valid}."
+                f"Path {cloud_path} does not begin with a known prefix {valid_prefixes}."
             )
 
-        # Otherwise instantiate as normal
-        new_obj = cls.__new__(cls, cloud_path, *args, **kwargs)
-        if isinstance(new_obj, cls):
-            cls.__init__(new_obj, cloud_path, *args, **kwargs)
+        new_obj = object.__new__(cls)
+        cls.__init__(new_obj, cloud_path, *args, **kwargs)  # type: ignore[type-var]
         return new_obj
 
     def __init__(cls, name: str, bases: Tuple[type, ...], dic: Dict[str, Any]) -> None:
@@ -449,7 +464,7 @@
         newline: Optional[str] = None,
         force_overwrite_from_cloud: bool = False,  # extra kwarg not in pathlib
         force_overwrite_to_cloud: bool = False,  # extra kwarg not in pathlib
-    ) -> IO:
+    ) -> IO[Any]:
         # if trying to call open on a directory that exists
         if self.exists() and not self.is_file():
             raise CloudPathIsADirectoryError(