core[patch]: add additionalProperties recursively to oai function if strict (#25169)

Hello. 
First of all, thank you for maintaining such a great project.

## Description
In https://github.com/langchain-ai/langchain/pull/25123, support for
structured_output is added. However, `"additionalProperties": false`
needs to be included at all levels when a nested object is generated.

error from current code:
https://gist.github.com/fufufukakaka/e9b475300e6934853d119428e390f204
```
BadRequestError: Error code: 400 - {'error': {'message': "Invalid schema for response_format 'JokeWithEvaluation': In context=('properties', 'self_evaluation'), 'additionalProperties' is required to be supplied and to be false", 'type': 'invalid_request_error', 'param': 'response_format', 'code': None}}
```

Reference: [Introducing Structured Outputs in the
API](https://openai.com/index/introducing-structured-outputs-in-the-api/)

```json
{
  "model": "gpt-4o-2024-08-06",
  "messages": [
    {
      "role": "system",
      "content": "You are a helpful math tutor."
    },
    {
      "role": "user",
      "content": "solve 8x + 31 = 2"
    }
  ],
  "response_format": {
    "type": "json_schema",
    "json_schema": {
      "name": "math_response",
      "strict": true,
      "schema": {
        "type": "object",
        "properties": {
          "steps": {
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "explanation": {
                  "type": "string"
                },
                "output": {
                  "type": "string"
                }
              },
              "required": ["explanation", "output"],
              "additionalProperties": false
            }
          },
          "final_answer": {
            "type": "string"
          }
        },
        "required": ["steps", "final_answer"],
        "additionalProperties": false
      }
    }
  }
}
```

In the current code, `"additionalProperties": false` is only added at
the last level.
This PR introduces the `_add_additional_properties_key` function, which
recursively adds `"additionalProperties": false` to the entire JSON
schema for the request.

Twitter handle: `@fukkaa1225`

Thank you!

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/core/langchain_core/utils/function_calling.py

@@ -389,9 +389,13 @@ def convert_to_openai_function(
 
     if strict is not None:
         oai_function["strict"] = strict
-        # As of 08/06/24, OpenAI requires that additionalProperties be supplied and set
-        # to False if strict is True.
-        oai_function["parameters"]["additionalProperties"] = False
+        if strict:
+            # As of 08/06/24, OpenAI requires that additionalProperties be supplied and
+            # set to False if strict is True.
+            # All properties layer needs 'additionalProperties=False'
+            oai_function["parameters"] = _recursive_set_additional_properties_false(
+                oai_function["parameters"]
+            )
     return oai_function
 
 
@@ -592,3 +596,20 @@ def _py_38_safe_origin(origin: Type) -> Type:
         **origin_union_type_map,
     }
     return cast(Type, origin_map.get(origin, origin))
+
+
+def _recursive_set_additional_properties_false(
+    schema: Dict[str, Any],
+) -> Dict[str, Any]:
+    if isinstance(schema, dict):
+        # Check if 'required' is a key at the current level
+        if "required" in schema:
+            schema["additionalProperties"] = False
+        # Recursively check 'properties' and 'items' if they exist
+        if "properties" in schema:
+            for value in schema["properties"].values():
+                _recursive_set_additional_properties_false(value)
+        if "items" in schema:
+            _recursive_set_additional_properties_false(schema["items"])
+
+    return schema

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

@@ -341,9 +341,7 @@ def test_convert_to_openai_function_nested() -> None:
                     "required": ["nested_arg1", "nested_arg2"],
                 },
             },
-            "required": [
-                "arg1",
-            ],
+            "required": ["arg1"],
         },
     }
 
@@ -351,6 +349,47 @@ def test_convert_to_openai_function_nested() -> None:
     assert actual == expected
 
 
+def test_convert_to_openai_function_nested_strict() -> None:
+    class Nested(BaseModel):
+        nested_arg1: int = Field(..., description="foo")
+        nested_arg2: Literal["bar", "baz"] = Field(
+            ..., description="one of 'bar', 'baz'"
+        )
+
+    def my_function(arg1: Nested) -> None:
+        """dummy function"""
+        pass
+
+    expected = {
+        "name": "my_function",
+        "description": "dummy function",
+        "parameters": {
+            "type": "object",
+            "properties": {
+                "arg1": {
+                    "type": "object",
+                    "properties": {
+                        "nested_arg1": {"type": "integer", "description": "foo"},
+                        "nested_arg2": {
+                            "type": "string",
+                            "enum": ["bar", "baz"],
+                            "description": "one of 'bar', 'baz'",
+                        },
+                    },
+                    "required": ["nested_arg1", "nested_arg2"],
+                    "additionalProperties": False,
+                },
+            },
+            "required": ["arg1"],
+            "additionalProperties": False,
+        },
+        "strict": True,
+    }
+
+    actual = convert_to_openai_function(my_function, strict=True)
+    assert actual == expected
+
+
 @pytest.mark.xfail(reason="Pydantic converts Optional[str] to str in .schema()")
 def test_function_optional_param() -> None:
     @tool

libs/partners/openai/tests/integration_tests/chat_models/test_base.py

@@ -868,6 +868,43 @@ def test_structured_output_strict(
         next(chat.stream("Tell me a joke about cats."))
 
 
+@pytest.mark.parametrize(
+    ("model", "method", "strict"), [("gpt-4o-2024-08-06", "json_schema", None)]
+)
+def test_nested_structured_output_strict(
+    model: str, method: Literal["json_schema"], strict: Optional[bool]
+) -> None:
+    """Test to verify structured output with strict=True for nested object."""
+
+    from typing import TypedDict
+
+    llm = ChatOpenAI(model=model, temperature=0)
+
+    class SelfEvaluation(TypedDict):
+        score: int
+        text: str
+
+    class JokeWithEvaluation(TypedDict):
+        """Joke to tell user."""
+
+        setup: str
+        punchline: str
+        self_evaluation: SelfEvaluation
+
+    # Schema
+    chat = llm.with_structured_output(JokeWithEvaluation, method=method, strict=strict)
+    result = chat.invoke("Tell me a joke about cats.")
+    assert isinstance(result, dict)
+    assert set(result.keys()) == {"setup", "punchline", "self_evaluation"}
+    assert set(result["self_evaluation"].keys()) == {"score", "text"}
+
+    for chunk in chat.stream("Tell me a joke about cats."):
+        assert isinstance(chunk, dict)
+    assert isinstance(chunk, dict)  # for mypy
+    assert set(chunk.keys()) == {"setup", "punchline", "self_evaluation"}
+    assert set(chunk["self_evaluation"].keys()) == {"score", "text"}
+
+
 def test_json_mode() -> None:
     llm = ChatOpenAI(model="gpt-4o-mini", temperature=0)
     response = llm.invoke(