openai[patch]: accept json schema response format directly (#27623)

fix #25460

---------

Co-authored-by: Erick Friis <erick@langchain.dev>

libs/partners/openai/langchain_openai/chat_models/base.py

@@ -1458,7 +1458,6 @@ class BaseChatOpenAI(BaseChatModel):
                     "schema must be specified when method is not 'json_mode'. "
                     "Received None."
                 )
-            strict = strict if strict is not None else True
             response_format = _convert_to_openai_response_format(schema, strict=strict)
             llm = self.bind(response_format=response_format)
             if is_pydantic_schema:
@@ -2139,14 +2138,32 @@ def _resize(width: int, height: int) -> Tuple[int, int]:
 
 
 def _convert_to_openai_response_format(
-    schema: Union[Dict[str, Any], Type], strict: bool
+    schema: Union[Dict[str, Any], Type], *, strict: Optional[bool] = None
 ) -> Union[Dict, TypeBaseModel]:
     if isinstance(schema, type) and is_basemodel_subclass(schema):
         return schema
+
+    if "json_schema" in schema and schema.get("type") == "json_schema":
+        response_format = schema
+    elif "name" in schema and "schema" in schema:
+        response_format = {"type": "json_schema", "json_schema": schema}
     else:
+        strict = strict if strict is not None else True
         function = convert_to_openai_function(schema, strict=strict)
         function["schema"] = function.pop("parameters")
-        return {"type": "json_schema", "json_schema": function}
+        response_format = {"type": "json_schema", "json_schema": function}
+
+    if strict is not None and strict is not response_format["json_schema"].get(
+        "strict"
+    ):
+        msg = (
+            f"Output schema already has 'strict' value set to "
+            f"{schema['json_schema']['strict']} but 'strict' also passed in to "
+            f"with_structured_output as {strict}. Please make sure that "
+            f"'strict' is only specified in one place."
+        )
+        raise ValueError(msg)
+    return response_format
 
 
 @chain

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

@@ -23,6 +23,7 @@ from langchain_openai import ChatOpenAI
 from langchain_openai.chat_models.base import (
     _convert_dict_to_message,
     _convert_message_to_dict,
+    _convert_to_openai_response_format,
     _create_usage_metadata,
     _format_message_content,
 )
@@ -761,3 +762,46 @@ def test__create_usage_metadata() -> None:
         input_token_details={},
         output_token_details={},
     )
+
+
+def test__convert_to_openai_response_format() -> None:
+    # Test response formats that aren't tool-like.
+    response_format: dict = {
+        "type": "json_schema",
+        "json_schema": {
+            "name": "math_reasoning",
+            "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,
+            },
+            "strict": True,
+        },
+    }
+
+    actual = _convert_to_openai_response_format(response_format)
+    assert actual == response_format
+
+    actual = _convert_to_openai_response_format(response_format["json_schema"])
+    assert actual == response_format
+
+    actual = _convert_to_openai_response_format(response_format, strict=True)
+    assert actual == response_format
+
+    with pytest.raises(ValueError):
+        _convert_to_openai_response_format(response_format, strict=False)