toTypedSchema fails to infer string from ZodEffects<ZodString, string, unknown>

[sschneider-ihre-pvs]

What happened?

When using z.preprocess(..., z.string()) in a Zod schema, the result is a ZodEffects<ZodString, string, unknown>. This is expected and correct behavior from Zod.

However, when this schema is passed into toTypedSchema() from @vee-validate/zod and used with useForm(), the field's value is incorrectly inferred as unknown, rather than the actual inner type (string in this case).

This breaks downstream usage with defineField()which then expose Ref instead of Ref, despite the Zod schema clearly specifying a string via transformation.

Reproduction steps

...

Version

Vue.js 3.x and vee-validate 4.x

What browsers are you seeing the problem on?

• Firefox
• Chrome
• Safari
• Microsoft Edge

Relevant log output

Demo link

https://play.vuejs.org/#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

Code of Conduct

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[rijenkii]

This is because z.input<typeof schema>["myField"] is unknown (playground):

import { z } from 'zod'; // types: 3

const schema = z.object({
  myField: z.preprocess(
    (val) => (typeof val === 'string' ? val : ''),
    z.string().min(1)
  ),
});

type X = z.input<typeof schema>["myField"];
//   ^? type X = unknown

Type of ReturnType<typeof useForm>["values"] is based on z.input of the schema, not z.output.