Add strict flag to the JSON parser (#9471)

This updates the default configuration since I think it's almost always
what we want to happen. But we should evaluate whether there are any issues.

libs/langchain/langchain/output_parsers/openai_functions.py

@@ -37,16 +37,32 @@ class OutputFunctionsParser(BaseGenerationOutputParser[Any]):
 class JsonOutputFunctionsParser(OutputFunctionsParser):
     """Parse an output as the Json object."""
 
+    strict: bool = False
+    """Whether to allow non-JSON-compliant strings.
+    
+    See: https://docs.python.org/3/library/json.html#encoders-and-decoders
+    
+    Useful when the parsed output may include unicode characters or new lines.
+    """
+
     def parse_result(self, result: List[Generation]) -> Any:
         function_call_info = super().parse_result(result)
         if self.args_only:
             try:
-                return json.loads(function_call_info)
+                return json.loads(function_call_info, strict=self.strict)
+            except (json.JSONDecodeError, TypeError) as exc:
+                raise OutputParserException(
+                    f"Could not parse function call data: {exc}"
+                )
+        else:
+            try:
+                function_call_info["arguments"] = json.loads(
+                    function_call_info["arguments"], strict=self.strict
+                )
             except (json.JSONDecodeError, TypeError) as exc:
                 raise OutputParserException(
                     f"Could not parse function call data: {exc}"
                 )
-        function_call_info["arguments"] = json.loads(function_call_info["arguments"])
             return function_call_info
 
 

libs/langchain/tests/unit_tests/output_parsers/test_openai_functions.py

@@ -1,4 +1,4 @@
-import json
+from typing import Any, Dict
 
 import pytest
 
@@ -9,40 +9,99 @@ from langchain.schema import BaseMessage, ChatGeneration, OutputParserException
 from langchain.schema.messages import AIMessage, HumanMessage
 
 
-@pytest.fixture
-def ai_message() -> AIMessage:
-    """Return a simple AIMessage."""
-    content = "This is a test message"
-
-    args = json.dumps(
-        {
-            "arg1": "value1",
+def test_json_output_function_parser() -> None:
+    """Test the JSON output function parser is configured with robust defaults."""
+    message = AIMessage(
+        content="This is a test message",
+        additional_kwargs={
+            "function_call": {
+                "name": "function_name",
+                "arguments": '{"arg1": "code\ncode"}',
             }
+        },
     )
-
-    function_call = {"name": "function_name", "arguments": args}
-    additional_kwargs = {"function_call": function_call}
-    return AIMessage(content=content, additional_kwargs=additional_kwargs)
-
-
-def test_json_output_function_parser(ai_message: AIMessage) -> None:
-    """Test that the JsonOutputFunctionsParser with full output."""
-    chat_generation = ChatGeneration(message=ai_message)
+    chat_generation = ChatGeneration(message=message)
 
     # Full output
+    # Test that the parsers defaults are configured to parse in non-strict mode
     parser = JsonOutputFunctionsParser(args_only=False)
     result = parser.parse_result([chat_generation])
-    assert result == {"arguments": {"arg1": "value1"}, "name": "function_name"}
+    assert result == {"arguments": {"arg1": "code\ncode"}, "name": "function_name"}
 
     # Args only
     parser = JsonOutputFunctionsParser(args_only=True)
     result = parser.parse_result([chat_generation])
-    assert result == {"arg1": "value1"}
+    assert result == {"arg1": "code\ncode"}
 
     # Verify that the original message is not modified
-    assert ai_message.additional_kwargs == {
-        "function_call": {"name": "function_name", "arguments": '{"arg1": "value1"}'}
+    assert message.additional_kwargs == {
+        "function_call": {
+            "name": "function_name",
+            "arguments": '{"arg1": "code\ncode"}',
         }
+    }
+
+
+@pytest.mark.parametrize(
+    "config",
+    [
+        {
+            "args_only": False,
+            "strict": False,
+            "args": '{"arg1": "value1"}',
+            "result": {"arguments": {"arg1": "value1"}, "name": "function_name"},
+            "exception": None,
+        },
+        {
+            "args_only": True,
+            "strict": False,
+            "args": '{"arg1": "value1"}',
+            "result": {"arg1": "value1"},
+            "exception": None,
+        },
+        {
+            "args_only": True,
+            "strict": False,
+            "args": '{"code": "print(2+\n2)"}',
+            "result": {"code": "print(2+\n2)"},
+            "exception": None,
+        },
+        {
+            "args_only": True,
+            "strict": False,
+            "args": '{"code": "你好)"}',
+            "result": {"code": "你好)"},
+            "exception": None,
+        },
+        {
+            "args_only": True,
+            "strict": True,
+            "args": '{"code": "print(2+\n2)"}',
+            "exception": OutputParserException,
+        },
+    ],
+)
+def test_json_output_function_parser_strictness(config: Dict[str, Any]) -> None:
+    """Test parsing with JSON strictness on and off."""
+    args = config["args"]
+
+    message = AIMessage(
+        content="This is a test message",
+        additional_kwargs={
+            "function_call": {"name": "function_name", "arguments": args}
+        },
+    )
+    chat_generation = ChatGeneration(message=message)
+
+    # Full output
+    parser = JsonOutputFunctionsParser(
+        strict=config["strict"], args_only=config["args_only"]
+    )
+    if config["exception"] is not None:
+        with pytest.raises(config["exception"]):
+            parser.parse_result([chat_generation])
+    else:
+        assert parser.parse_result([chat_generation]) == config["result"]
 
 
 @pytest.mark.parametrize(