Handle empty function call metadata arguments

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 9b232bff-6a8c-4b02-addd-89de57a82f6a

Author: cecheta

python/packages/foundry_hosting/agent_framework_foundry_hosting/_responses.py

@@ -996,11 +996,7 @@ def handle(self, content: Content) -> Generator[ResponseStreamEvent]:
                     yield self._summary_part.emit_text_delta(content.text)
 
         elif content.type == "function_call" and content.call_id is not None:
-            if (
-                content.user_input_request
-                and content.arguments is None
-                and content.call_id in self._seen_function_call_ids
-            ):
+            if content.user_input_request and not content.arguments and content.call_id in self._seen_function_call_ids:
                 return
             if self._active_type != "function_call" or self._active_id != content.call_id:
                 yield from self._close()

python/packages/foundry_hosting/tests/test_responses.py

@@ -1265,8 +1265,11 @@ async def test_function_call_streaming(self) -> None:
         assert len(args_done) == 1
         assert args_done[0]["data"]["arguments"] == '{"q": "hello"}'
 
-    async def test_declaration_only_metadata_does_not_duplicate_streamed_function_call(self) -> None:
-        metadata = Content.from_function_call("call_1", "search", arguments=None)
+    @pytest.mark.parametrize("arguments", [None, ""])
+    async def test_declaration_only_metadata_does_not_duplicate_streamed_function_call(
+        self, arguments: str | None
+    ) -> None:
+        metadata = Content.from_function_call("call_1", "search", arguments=arguments)
         metadata.id = "call_1"
         metadata.user_input_request = True
         agent = _make_agent(