[v2] looseSchema rejects a Zod validator containing optional object properties in validators.run #2475

Describe the bug

Tested on @tanstack/react-form@2.0.0-alpha.3: When using formOptions.looseSchema, a Zod schema containing an optional object property is accepted as the loose schema but rejected when the same schema is passed to validators[].run.

The reported type error indicates that InferUnionObject changes an optional property such as:

text?: string | undefined;

into a required property whose value may be undefined:

text: string | undefined;

The same Zod schema can consequently not be used as the runtime validator.

Reproduction

import { formOptions, useForm } from '@tanstack/react-form';
import z from 'zod';

const schema = z.object({
	myProp: z.string().optional(),
});

const Test = () => {
  const form = useForm(
    formOptions.looseSchema(schema, {
      defaultValues: {},
      validators: [
        {
          triggers: ['change'],
          run: schema, // throws error
        },
      ],
    }),
  );
  return form;
};

TypeScript error

[...] Property 'myProp' is optional in type '{ myProp?: string | undefined; }' but required in type 'InferUnionObject<{}, { myProp?: string | undefined; }>'

Your minimal, reproducible example

https://stackblitz.com/edit/vitejs-vite-pg3hqj4e?file=src%2FForm.tsx&terminal=dev

Steps to reproduce

import { formOptions, useForm } from '@tanstack/react-form'; // v2 alpha 3
import z from 'zod';

const schema = z.object({
	myProp: z.string().optional(),
});

const Test = () => {
  const form = useForm(
    formOptions.looseSchema(schema, {
      defaultValues: {},
      validators: [
        {
          triggers: ['change'],
          run: schema, // throws error
        },
      ],
    }),
  );
  return form;
};

Expected behavior

The schema passed to formOptions.looseSchema should also be accepted as a validator in validators[].run.

In particular, an optional schema property:

myProp?: string;

should remain compatible with the editable loose-schema representation, where the property may be omitted or contain undefined.

How often does this bug happen?

Always

Screenshots or Videos

No response

Platform

Linux

TanStack Form adapter

react-form

TanStack Form version

2.0.0-alpha.3

TypeScript version

7.0.2

Additional context

No response