fix: structured output parser

[anadi45]

Fixes #(6734)

1. Capture JSON object using outer curly brackets.
2. Fix existing integration tests

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[jacoblee93]

Hey @anadi45, thanks for this!

Am a bit nervous about swapping this out wholesale since LLMs could perhaps output curly braces in other contexts and I wouldn't want to break anyone depending on the old behavior - what is the issue you are encountering?

At minimum this needs a lot more unit tests.

[anadi45]

Hi @jacoblee93, thank you so much for the review! I'm new to open source and wanted to contribute to LangChain since we use it at our organization. I chose this issue as a starting point where the parser currently breaks if there are nested triple backticks.

I agree that changing the parsing logic entirely could be risky. To maintain backward compatibility, I could incorporate my logic within a catch block, and only throw an error if both approaches fail. I’ll also explore alternative ways to handle this issue.

If you have any other suggestions, I’d be happy to incorporate them! Regardless, I'll add more test cases to cover these scenarios.

[jacoblee93]

Hey @anadi45, sounds good - please ping again when ready.

[anadi45]

@jacoblee93 should I close this? Looks like #7199 already solved this issue.