JSON.parse() - How to handle throwable error in safeParse?

[enheit]

I have such schema

export const Schema = object({
  nextCursor: optional(
    transform(string(), (input) => { 
      try { 
        return JSON.parse(input) as Record<string, string> 
      } catch { 
        // What to return here? Error? ValidError? String?
      } 
    },
  ))
})

And use it like this

const nextKey = "{ \"hasNext\": \"true\" }";
const result = v.safeParse(Schema, { nextKey });

If JSON.parse(...) throws an error, how can I notify a Valibot that this error is expected and just return a message like "JSON parse failed" inside result.issues? Currently (without a try/catch), it throws an error, and safeParse doesn't handle it.

[fabian-hiller]

Unfortunately, we do not have a perfect answer to this. But you could try to return the input and use the third argument of transform to validate its output.

[enheit]

Could you provide a little example of how to do this? I don't quite understand what this means

use the third argument of transform to validate its output

Thanks

[fabian-hiller]

const Schema = v.object({
  nextCursor: v.optional(
    v.transform(
      v.string(),
      (input) => {
        try {
          return JSON.parse(input) as Record<string, string>;
        } catch {
          return null;
        }
      },
      v.record(v.string(), 'Optional errer message here') // <--
    )
  ),
});