Langchain output parser fails to parse nested objects inside array.

[wadood42]

This is my Zod Schema:
const parser = StructuredOutputParser.fromZodSchema(
z.array(
z.object({
title: z.string(),
introduction: z.string(),
body: z.array(
z.object({
title: z.string(),
text: z.string(),
})
),
conclusion: z.string(),
})
)
);

llms's output:

[
  {
    "title": "How to Become a Better Runner",
    "introduction": "Running can be a great way to stay fit and healthy. It is also a great way to challenge yourself and push your limits. Whether you are a beginner looking to get started or an experienced runner looking to take your training to the next level, there are all kinds of tips and tricks that can help you become a better runner. In this blog post, we will explore four of the most important steps to improving your running performance.",
    "body": [
      {
        "title": "Find/Set Goals",
        "text": "Start by setting yourself some realistic and achievable goals. These goals don’t have to be marathon distance goals, they just need to be something that you can work towards. This could be a specific time you want to run a mile in or a certain distance you want to cover. Having these goals in mind will give you something to work towards and will help you stay motivated during your training."
      },
      {
        "title": "Train and Rest",
        "text": "Training hard and pushing yourself is an important part of improving as a runner, but it is also important to recognize when it is time to take a break. Make sure you are training regularly, but also giving yourself a chance to rest and recover. Listening to your body is key and recognizing when it is time to take a break will allow you to avoid injury and come back stronger than ever."
      },
      {
        "title": "Eat Right",
        "text": "Proper nutrition is essential for any athlete. Make sure you are eating a balanced diet that fuels your body and gives you the energy to get out and run. Eating right can also help reduce your risk of injury and keep your body healthy."
      },
      {
        "title": "Stay Motivated",
        "text": "Motivation is key when it comes to running. Whether you find motivation from a running partner or an inspiring podcast, find something that inspires you and keeps you focused on your goals. Remember, the only way to achieve your goals is to put in the hard work and stay committed to the process."
      }
    ],
    "conclusion": "Improving as a runner requires discipline, hard work, and dedication. If you follow these four steps, you’ll be on your way to becoming a better runner in no time!"
  }
]

**Parsed response** [
  {
    title: 'How to Become a Better Runner',
    introduction: 'Running can be a great way to stay fit and healthy. It is also a great way to challenge yourself and push your limits. Whether you are a beginner looking to get started or an experienced runner looking to take your training to the next level, there are all kinds of tips and tricks that can help you become a better runner. In this blog post, we will explore four of the most important steps to improving your running performance.',
    body: [ [Object], [Object], [Object], [Object] ],
    conclusion: 'Improving as a runner requires discipline, hard work, and dedication. If you follow these four steps, you’ll be on your way to becoming a better runner in no time!'
  }
]

[jacoblee93]

Can you log it with JSON.stringify(response, null, 2)?

[wadood42]

The response (response) from llm is string.

this is the parser which will be used to parse the response.
const parser = StructuredOutputParser.fromZodSchema(
z.array(
z.object({
title: z.string(),
introduction: z.string(),
body: z.array(
z.object({
title: z.string(),
text: z.string(),
})
),
conclusion: z.string(),
})
)
);

and when i try to parse it it does not parse the objects inside array.
const parsed = await parser.parse(response).
this is the response after parsing it.[
{
title: 'How to Become a Better Runner',
introduction: 'Running can be a great way to stay fit and healthy. It is also a great way to challenge yourself and push your limits. Whether you are a beginner looking to get started or an experienced runner looking to take your training to the next level, there are all kinds of tips and tricks that can help you become a better runner. In this blog post, we will explore four of the most important steps to improving your running performance.',
body: [ [Object], [Object], [Object], [Object] ],
conclusion: 'Improving as a runner requires discipline, hard work, and dedication. If you follow these four steps, you’ll be on your way to becoming a better runner in no time!'
}
]

[simpel]

Hi @wadood42 I know its an old thread but I have the same issue. Did you find a solution?

[jacoblee93]

Hey @simpel can you share your code and your package.json file?

We generally suggest people use .withStructuredOutput for models that support it now:

https://js.langchain.com/docs/how_to/structured_output/#the-.withstructuredoutput-method