Do not erase function types in decorators (#135)

* fixup! Do not erase function types in decorators

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/lightning_utilities/core/imports.py

@@ -8,11 +8,15 @@
 from functools import lru_cache
 from importlib.util import find_spec
 from types import ModuleType
-from typing import Any, Callable, List, Optional
+from typing import Any, Callable, List, Optional, TypeVar
 
 import pkg_resources
 from packaging.requirements import Requirement
 from packaging.version import Version
+from typing_extensions import ParamSpec
+
+T = TypeVar("T")
+P = ParamSpec("P")
 
 try:
     from importlib import metadata
@@ -260,7 +264,7 @@ def lazy_import(module_name: str, callback: Optional[Callable] = None) -> LazyMo
     return LazyModule(module_name, callback=callback)
 
 
-def requires(*module_path: str, raise_exception: bool = True) -> Callable:
+def requires(*module_path: str, raise_exception: bool = True) -> Callable[[Callable[P, T]], Callable[P, T]]:
     """Wrap early import failure with some nice exception message.
 
     Example:
@@ -277,15 +281,15 @@ def requires(*module_path: str, raise_exception: bool = True) -> Callable:
         ...         self._rnd = pow(randint(1, 9), 2)
     """
 
-    def decorator(func: Callable) -> Callable:
+    def decorator(func: Callable[P, T]) -> Callable[P, T]:
         @functools.wraps(func)
-        def wrapper(*args: Any, **kwargs: Any) -> Any:
+        def wrapper(*args: P.args, **kwargs: P.kwargs) -> T:
             unavailable_modules = [module for module in module_path if not module_available(module)]
             if any(unavailable_modules):
                 msg = f"Required dependencies not available. Please run `pip install {' '.join(unavailable_modules)}`"
                 if raise_exception:
                     raise ModuleNotFoundError(msg)
-                warnings.warn(msg)
+                warnings.warn(msg, stacklevel=2)
             return func(*args, **kwargs)
 
         return wrapper

src/lightning_utilities/core/rank_zero.py

@@ -7,19 +7,24 @@
 import warnings
 from functools import wraps
 from platform import python_version
-from typing import Any, Callable, Optional, Union
+from typing import Any, Callable, Optional, TypeVar, Union
+
+from typing_extensions import ParamSpec
 
 log = logging.getLogger(__name__)
 
+T = TypeVar("T")
+P = ParamSpec("P")
+
 
-def rank_zero_only(fn: Callable) -> Callable:
+def rank_zero_only(fn: Callable[P, T]) -> Callable[P, Optional[T]]:
     """Wrap a function to call internal function only in rank zero.
 
     Function that can be used as a decorator to enable a function/method being called only on global rank 0.
     """
 
     @wraps(fn)
-    def wrapped_fn(*args: Any, **kwargs: Any) -> Optional[Any]:
+    def wrapped_fn(*args: P.args, **kwargs: P.kwargs) -> Optional[T]:
         rank = getattr(rank_zero_only, "rank", None)
         if rank is None:
             raise RuntimeError("The `rank_zero_only.rank` needs to be set before use")