langchain: add partial parsing support to JsonOutputToolsParser (#17035)

- **Description:** Add partial parsing support to JsonOutputToolsParser
- **Issue:**
[16736](https://github.com/langchain-ai/langchain/issues/16736)

---------

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>

libs/langchain/langchain/output_parsers/openai_tools.py

@@ -4,9 +4,8 @@ from json import JSONDecodeError
 from typing import Any, List, Type
 
 from langchain_core.exceptions import OutputParserException
-from langchain_core.output_parsers import (
-    BaseGenerationOutputParser,
-)
+from langchain_core.output_parsers import BaseGenerationOutputParser
+from langchain_core.output_parsers.json import parse_partial_json
 from langchain_core.outputs import ChatGeneration, Generation
 from langchain_core.pydantic_v1 import BaseModel
 
@@ -42,9 +41,14 @@ class JsonOutputToolsParser(BaseGenerationOutputParser[Any]):
             if "function" not in tool_call:
                 continue
             try:
-                function_args = json.loads(
-                    tool_call["function"]["arguments"], strict=self.strict
-                )
+                if partial:
+                    function_args = parse_partial_json(
+                        tool_call["function"]["arguments"], strict=self.strict
+                    )
+                else:
+                    function_args = json.loads(
+                        tool_call["function"]["arguments"], strict=self.strict
+                    )
             except JSONDecodeError as e:
                 exceptions.append(
                     f"Function {tool_call['function']['name']} arguments:\n\n"
@@ -77,7 +81,7 @@ class JsonOutputKeyToolsParser(JsonOutputToolsParser):
         super().__init__(key_name=key_name, **kwargs)
 
     def parse_result(self, result: List[Generation], *, partial: bool = False) -> Any:
-        results = super().parse_result(result)
+        results = super().parse_result(result, partial=partial)
         results = [res for res in results if res["type"] == self.key_name]
         if not self.return_id:
             results = [res["args"] for res in results]
@@ -92,6 +96,6 @@ class PydanticToolsParser(JsonOutputToolsParser):
     tools: List[Type[BaseModel]]
 
     def parse_result(self, result: List[Generation], *, partial: bool = False) -> Any:
-        results = super().parse_result(result)
+        results = super().parse_result(result, partial=partial)
         name_dict = {tool.__name__: tool for tool in self.tools}
         return [name_dict[res["type"]](**res["args"]) for res in results]