fix: use functools.wraps in activity_tool to preserve metadata (#1636)

Replace manual metadata copying with @functools.wraps(activity_def) to
preserve __annotations__, __module__, __qualname__, and __dict__ on the
wrapper function. These are needed by ADK's tool schema generation
(specifically _handle_params_as_deferred_annotations) to resolve type
hints from the original activity function.

Also adds test_activity_tool_preserves_metadata verifying that
__name__, __doc__, __annotations__, __module__, and __signature__
are all correctly preserved on the wrapper.

Fixes #1635

Co-authored-by: Brian Strauch <brian@brianstrauch.com>

Author: brucearctor

temporalio/contrib/google_adk_agents/workflow.py

@@ -1,5 +1,6 @@
 """Workflow utilities for Google ADK agents integration with Temporal."""
 
+import functools
 import inspect
 from typing import Any, Callable
 
@@ -18,6 +19,7 @@ def activity_tool(activity_def: Callable, **kwargs: Any) -> Callable:
     while marking it as a tool that executes via 'workflow.execute_activity'.
     """
 
+    @functools.wraps(activity_def)
     async def wrapper(*args: Any, **kw: Any):
         # Inspect signature to bind arguments
         sig = inspect.signature(activity_def)
@@ -48,9 +50,8 @@ async def wrapper(*args: Any, **kw: Any):
             activity_def, args=activity_args, **options
         )
 
-    # Copy metadata
-    wrapper.__name__ = activity_def.__name__
-    wrapper.__doc__ = activity_def.__doc__
+    # functools.wraps copies name/doc/module/annotations/qualname/dict.
+    # Signature must be set explicitly since the wrapper uses *args/**kw.
     setattr(wrapper, "__signature__", inspect.signature(activity_def))
 
     return wrapper

tests/contrib/google_adk_agents/test_google_adk_agents.py

@@ -14,6 +14,7 @@
 
 """Integration tests for ADK Temporal support."""
 
+import inspect
 import json
 import logging
 import os
@@ -1119,3 +1120,41 @@ def test_explicitly_set_none_preserved() -> None:
 
     assert "cache_config" in serialized, "Explicitly-set None should be preserved"
     assert serialized["cache_config"] is None
+
+
+def test_activity_tool_preserves_metadata() -> None:
+    """activity_tool wrapper preserves the original function's metadata.
+
+    This ensures ADK's tool schema generation can inspect __annotations__
+    and __module__ on the wrapper, which are needed by
+    ``_handle_params_as_deferred_annotations`` to resolve type hints.
+    """
+
+    @activity.defn
+    async def my_activity(city: str, count: int = 1) -> str:
+        """Get info for a city."""
+        return f"{city}: {count}"
+
+    tool = temporalio.contrib.google_adk_agents.workflow.activity_tool(
+        my_activity, start_to_close_timeout=timedelta(seconds=30)
+    )
+
+    # __name__ and __doc__
+    assert tool.__name__ == "my_activity"
+    assert tool.__doc__ == "Get info for a city."
+
+    # __annotations__ — critical for ADK type introspection
+    assert "city" in tool.__annotations__
+    assert tool.__annotations__["city"] is str
+    assert tool.__annotations__["count"] is int
+    assert tool.__annotations__["return"] is str
+
+    # __module__ — needed by _handle_params_as_deferred_annotations
+    assert tool.__module__ == my_activity.__module__
+
+    # __signature__ — must match the original, not *args/**kw
+    sig = inspect.signature(tool)
+    params = list(sig.parameters.keys())
+    assert params == ["city", "count"]
+    assert sig.parameters["city"].annotation is str
+    assert sig.parameters["count"].default == 1