[Exception Handling] DeepSeek JSONDecodeError

[AhmedTammaa]

For Context please check #29626

The Deepseek is using langchain_openai. The error happens that it show json decode error.

I added a handler for this to give a more sensible error message which is DeepSeek API returned empty/invalid json.

Reproducing the issue is a bit challenging as it is inconsistent, sometimes DeepSeek returns valid data and in other times it returns invalid data which triggers the JSON Decode Error.

This PR is an exception handling, but not an ultimate fix for the issue.

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[ccurme]

This is a problem with DeepSeek. I don't think we should handle this in langchain-openai (there are many providers who subclass BaseChatOpenAI, it's not tenable to account for these possibilities for all providers).

What do you think about implementing this on ChatDeepSeek-- e.g., overriding _stream and other methods and handling exceptions when you call super()._stream?

[AhmedTammaa]

Aha, thank you @ccurme, I didn't know that it is used by others other than Openai and Deepseek. You are absolutely right about your concern. I will make the suggested changes and revert the BaseChatOpenAI changes.

[AhmedTammaa]

@ccurme I have made the changes as suggested. However, I need an advice here: Should I raise the error as ValueError as we have it from the parent class or JSONDecodeError?

please note I did a small refactor in the function _create_chat_result the ruff formatter was moving the type ignore comment so it was triggering the linting checker.