Handling JSONDecodeError; Invalid /escape in JsonOutputParser

[hadifar]

Checked other resources

• I added a very descriptive title to this issue.
• I searched the LangChain documentation with the integrated search.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

Example Code

import json

from langchain_core.output_parsers import JsonOutputParser
from langchain_core.runnables import RunnableLambda

def fake_llm1(inputs):
    return json.dumps(str({
                              "response": "The user question does not align with the structure or data within our database tables. The tables are relational in terms and follow the naming convention of 'galvatron\' or'mac_\', however the user question appears unrelated to the type of data and structure of the tables."}))


def fake_llm2(inputs):
    return str({
        "response": "The user question does not align with the structure or data within our database tables. The tables are relational in terms and follow the naming convention of 'galvatron\' or'mac_\', however the user question appears unrelated to the type of data and structure of the tables."})


chain1 = RunnableLambda(fake_llm1) | JsonOutputParser()
chain2 = RunnableLambda(fake_llm2) | JsonOutputParser()

# execute 
print(chain1.invoke(""))
# throw exception
print(chain2.invoke(""))

Error Message and Stack Trace (if applicable)

return super().parse_result(result, partial=partial)

File "langchain_core\output_parsers\json.py", line 87, in parse_result
raise OutputParserException(msg, llm_output=text) from e
langchain_core.exceptions.OutputParserException: Invalid json output: {'response': "The user question does not align with the structure or data within our database tables. The tables are relational in terms and follow the naming convention of 'galvatron' or'mac_', however the user question appears unrelated to the type of data and structure of the tables."}

Description

I'm not entirely sure if it is a bug. I found it really strange that when string contains escape character we have such an issue. We can resolve the issue by dumping it to JSON first.

System Info

System Information

OS: Windows
OS Version: 10.0.19045
Python Version: 3.10.10 (tags/v3.10.10:aad5f6a, Feb 7 2023, 17:20:36) [MSC v.1929 64 bit (AMD64)]

Package Information

langchain_core: 0.3.1
langchain: 0.3.0
langchain_community: 0.3.0
langsmith: 0.1.123
langchain_experimental: 0.0.55
langchain_huggingface: 0.1.0
langchain_nomic: 0.1.2
langchain_ollama: 0.1.0
langchain_openai: 0.1.20
langchain_text_splitters: 0.3.0
langchainhub: 0.1.20
langgraph: 0.2.22

[ashvin-a]

I'm not sure whether this is a bug. @eyurtsev What do you think?

[mgs28]

This is a python issue with str and json. str() by design converts python dictionaries to use single quotes for keys which is not allowed in json spec. When you try to loads a str() of a dictionary then you will get a JSONParse error.

JsonOutputParser() could handle this with replacing all single quotes with double quotes but that carries some risk. The json utility already has to handle mismatched quotes, etc. It feels unlikely that an LLM returns a json with single quoted properties. FYI - @ashvin-a @eyurtsev