core[patch]: handle some optional cases in tools (#16954)

primary problem in pydantic still exists, where `Optional[str]` gets
turned to `string` in the jsonschema `.schema()`

Also fixes the `SchemaSchema` naming issue

---------

Co-authored-by: William Fu-Hinthorn <13333726+hinthornw@users.noreply.github.com>

libs/core/langchain_core/tools.py

@@ -39,14 +39,21 @@ class SchemaAnnotationError(TypeError):
 
 
 def _create_subset_model(
-    name: str, model: BaseModel, field_names: list
+    name: str, model: Type[BaseModel], field_names: list
 ) -> Type[BaseModel]:
     """Create a pydantic model with only a subset of model's fields."""
     fields = {}
     for field_name in field_names:
         field = model.__fields__[field_name]
-        fields[field_name] = (field.outer_type_, field.field_info)
-    return create_model(name, **fields)  # type: ignore
+        t = (
+            # this isn't perfect but should work for most functions
+            field.outer_type_
+            if field.required and not field.allow_none
+            else Optional[field.outer_type_]
+        )
+        fields[field_name] = (t, field.field_info)
+    rtn = create_model(name, **fields)  # type: ignore
+    return rtn
 
 
 def _get_filtered_args(
@@ -764,7 +771,8 @@ class StructuredTool(BaseTool):
         description = f"{name}{sig} - {description.strip()}"
         _args_schema = args_schema
         if _args_schema is None and infer_schema:
-            _args_schema = create_schema_from_function(f"{name}Schema", source_function)
+            # schema name is appended within function
+            _args_schema = create_schema_from_function(name, source_function)
         return cls(
             name=name,
             func=func,

libs/core/tests/unit_tests/test_tools.py

@@ -1,4 +1,5 @@
 """Test the base tool implementation."""
+
 import json
 from datetime import datetime
 from enum import Enum
@@ -18,6 +19,7 @@ from langchain_core.tools import (
     StructuredTool,
     Tool,
     ToolException,
+    _create_subset_model,
     tool,
 )
 from tests.unit_tests.fake.callbacks import FakeCallbackHandler
@@ -321,7 +323,7 @@ def test_structured_tool_from_function_docstring() -> None:
             "bar": {"title": "Bar", "type": "integer"},
             "baz": {"title": "Baz", "type": "string"},
         },
-        "title": "fooSchemaSchema",
+        "title": "fooSchema",
         "type": "object",
         "required": ["bar", "baz"],
     }
@@ -354,7 +356,7 @@ def test_structured_tool_from_function_docstring_complex_args() -> None:
             "bar": {"title": "Bar", "type": "integer"},
             "baz": {"title": "Baz", "type": "array", "items": {"type": "string"}},
         },
-        "title": "fooSchemaSchema",
+        "title": "fooSchema",
         "type": "object",
         "required": ["bar", "baz"],
     }
@@ -454,7 +456,7 @@ def test_structured_tool_from_function_with_run_manager() -> None:
             "bar": {"title": "Bar", "type": "integer"},
             "baz": {"title": "Baz", "type": "string"},
         },
-        "title": "fooSchemaSchema",
+        "title": "fooSchema",
         "type": "object",
         "required": ["bar", "baz"],
     }
@@ -685,7 +687,7 @@ def test_structured_tool_from_function() -> None:
     }
 
     assert structured_tool.args_schema.schema() == {
-        "title": "fooSchemaSchema",
+        "title": "fooSchema",
         "type": "object",
         "properties": {
             "bar": {"title": "Bar", "type": "integer"},
@@ -821,3 +823,51 @@ async def test_async_validation_error_handling_non_validation_error(
     _tool = _RaiseNonValidationErrorTool(handle_validation_error=handler)
     with pytest.raises(NotImplementedError):
         await _tool.arun({})
+
+
+def test_optional_subset_model_rewrite() -> None:
+    class MyModel(BaseModel):
+        a: Optional[str]
+        b: str
+        c: Optional[List[Optional[str]]]
+
+    model2 = _create_subset_model("model2", MyModel, ["a", "b", "c"])
+
+    assert "a" not in model2.schema()["required"]  # should be optional
+    assert "b" in model2.schema()["required"]  # should be required
+    assert "c" not in model2.schema()["required"]  # should be optional
+
+
+@pytest.mark.parametrize(
+    "inputs, expected",
+    [
+        # Check not required
+        ({"bar": "bar"}, {"bar": "bar", "baz": 3, "buzz": "buzz"}),
+        # Check overwritten
+        (
+            {"bar": "bar", "baz": 4, "buzz": "not-buzz"},
+            {"bar": "bar", "baz": 4, "buzz": "not-buzz"},
+        ),
+        # Check validation error when missing
+        ({}, None),
+        # Check validation error when wrong type
+        ({"bar": "bar", "baz": "not-an-int"}, None),
+        # Check OK when None explicitly passed
+        ({"bar": "bar", "baz": None}, {"bar": "bar", "baz": None, "buzz": "buzz"}),
+    ],
+)
+def test_tool_invoke_optional_args(inputs: dict, expected: Optional[dict]) -> None:
+    @tool
+    def foo(bar: str, baz: Optional[int] = 3, buzz: Optional[str] = "buzz") -> dict:
+        """The foo."""
+        return {
+            "bar": bar,
+            "baz": baz,
+            "buzz": buzz,
+        }
+
+    if expected is not None:
+        assert foo.invoke(inputs) == expected  # type: ignore
+    else:
+        with pytest.raises(ValidationError):
+            foo.invoke(inputs)  # type: ignore

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

@@ -1,9 +1,9 @@
-from typing import Any, Callable, Literal, Type
+from typing import Any, Callable, List, Literal, Optional, Type
 
 import pytest
 
 from langchain_core.pydantic_v1 import BaseModel, Field
-from langchain_core.tools import BaseTool
+from langchain_core.tools import BaseTool, tool
 from langchain_core.utils.function_calling import convert_to_openai_function
 
 
@@ -33,7 +33,7 @@ def function() -> Callable:
 
 
 @pytest.fixture()
-def tool() -> BaseTool:
+def dummy_tool() -> BaseTool:
     class Schema(BaseModel):
         arg1: int = Field(..., description="foo")
         arg2: Literal["bar", "baz"] = Field(..., description="one of 'bar', 'baz'")
@@ -50,7 +50,7 @@ def tool() -> BaseTool:
 
 
 def test_convert_to_openai_function(
-    pydantic: Type[BaseModel], function: Callable, tool: BaseTool
+    pydantic: Type[BaseModel], function: Callable, dummy_tool: BaseTool
 ) -> None:
     expected = {
         "name": "dummy_function",
@@ -69,6 +69,22 @@ def test_convert_to_openai_function(
         },
     }
 
-    for fn in (pydantic, function, tool, expected):
+    for fn in (pydantic, function, dummy_tool, expected):
         actual = convert_to_openai_function(fn)  # type: ignore
         assert actual == expected
+
+
+@pytest.mark.xfail(reason="Pydantic converts Optional[str] to str in .schema()")
+def test_function_optional_param() -> None:
+    @tool
+    def func5(
+        a: Optional[str],
+        b: str,
+        c: Optional[List[Optional[str]]],
+    ) -> None:
+        """A test function"""
+        pass
+
+    func = convert_to_openai_function(func5)
+    req = func["parameters"]["required"]
+    assert set(req) == {"b"}