core,integrations[minor]: Dont error on fields in model_kwargs (#27110)

Given the current erroring behavior, every time we've moved a kwarg from
model_kwargs and made it its own field that was a breaking change.
Updating this behavior to support the old instantiations /
serializations.

Assuming build_extra_kwargs was not something that itself is being used
externally and needs to be kept backwards compatible

libs/core/langchain_core/utils/__init__.py

@@ -32,6 +32,7 @@ from langchain_core.utils.utils import (
 )
 
 __all__ = [
+    "build_extra_kwargs",
     "StrictFormatter",
     "check_package_version",
     "convert_to_secret_str",
@@ -46,7 +47,6 @@ __all__ = [
     "raise_for_status_with_text",
     "xor_args",
     "try_load_from_hub",
-    "build_extra_kwargs",
     "image",
     "get_from_env",
     "get_from_dict_or_env",

libs/core/langchain_core/utils/utils.py

@@ -210,6 +210,51 @@ def get_pydantic_field_names(pydantic_cls: Any) -> set[str]:
     return all_required_field_names
 
 
+def _build_model_kwargs(
+    values: dict[str, Any],
+    all_required_field_names: set[str],
+) -> dict[str, Any]:
+    """Build "model_kwargs" param from Pydanitc constructor values.
+
+    Args:
+        values: All init args passed in by user.
+        all_required_field_names: All required field names for the pydantic class.
+
+    Returns:
+        Dict[str, Any]: Extra kwargs.
+
+    Raises:
+        ValueError: If a field is specified in both values and extra_kwargs.
+        ValueError: If a field is specified in model_kwargs.
+    """
+    extra_kwargs = values.get("model_kwargs", {})
+    for field_name in list(values):
+        if field_name in extra_kwargs:
+            raise ValueError(f"Found {field_name} supplied twice.")
+        if field_name not in all_required_field_names:
+            warnings.warn(
+                f"""WARNING! {field_name} is not default parameter.
+                {field_name} was transferred to model_kwargs.
+                Please confirm that {field_name} is what you intended.""",
+                stacklevel=7,
+            )
+            extra_kwargs[field_name] = values.pop(field_name)
+
+    invalid_model_kwargs = all_required_field_names.intersection(extra_kwargs.keys())
+    if invalid_model_kwargs:
+        warnings.warn(
+            f"Parameters {invalid_model_kwargs} should be specified explicitly. "
+            f"Instead they were passed in as part of `model_kwargs` parameter.",
+            stacklevel=7,
+        )
+        for k in invalid_model_kwargs:
+            values[k] = extra_kwargs.pop(k)
+
+    values["model_kwargs"] = extra_kwargs
+    return values
+
+
+# DON'T USE! Kept for backwards-compatibility but should never have been public.
 def build_extra_kwargs(
     extra_kwargs: dict[str, Any],
     values: dict[str, Any],

libs/core/tests/unit_tests/utils/test_imports.py

@@ -17,8 +17,8 @@ EXPECTED_ALL = [
     "raise_for_status_with_text",
     "xor_args",
     "try_load_from_hub",
-    "build_extra_kwargs",
     "image",
+    "build_extra_kwargs",
     "get_from_dict_or_env",
     "get_from_env",
     "stringify_dict",