Fix: issue #1297: datasaver does not work with __future__.annotations

hamilton/function_modifiers/adapters.py

@@ -854,8 +854,8 @@ def save_json_data(data: pd.DataFrame, json_path: str = "data/my_saved_data.json
 
     def validate(self, fn: Callable):
         """Validates that the function output is a dict type."""
-        return_annotation = inspect.signature(fn).return_annotation
-        if return_annotation is inspect.Signature.empty:
+        return_annotation = typing.get_type_hints(fn)["return"]
+        if return_annotation is None:
             raise InvalidDecoratorException(
                 f"Function: {fn.__qualname__} must have a return annotation."
             )

tests/function_modifiers/test_adapters.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import dataclasses
 from collections import Counter
 from typing import Any, Collection, Dict, List, Tuple, Type