core[patch]: check for model_fields attribute (#25108)

`__fields__` raises a warning in pydantic v2

libs/core/langchain_core/tools.py

@@ -1666,7 +1666,10 @@ def _get_all_basemodel_annotations(
         for name, param in inspect.signature(cls).parameters.items():
             # Exclude hidden init args added by pydantic Config. For example if
             # BaseModel(extra="allow") then "extra_data" will part of init sig.
-            if (fields := getattr(cls, "__fields__", {})) and name not in fields:
+            if (
+                fields := getattr(cls, "model_fields", {})  # pydantic v2+
+                or getattr(cls, "__fields__", {})  # pydantic v1
+            ) and name not in fields:
                 continue
             annotations[name] = param.annotation
         orig_bases: Tuple = getattr(cls, "__orig_bases__", tuple())

libs/core/tests/unit_tests/test_tools.py

@@ -1746,6 +1746,7 @@ def test__is_message_content_type(obj: Any, expected: bool) -> None:
 
 @pytest.mark.skipif(PYDANTIC_MAJOR_VERSION != 2, reason="Testing pydantic v2.")
 @pytest.mark.parametrize("use_v1_namespace", [True, False])
+@pytest.mark.filterwarnings("error")
 def test__get_all_basemodel_annotations_v2(use_v1_namespace: bool) -> None:
     A = TypeVar("A")