issue: [zod v4][zod resolver] error on nested discriminated unions

[johnyvelho]

Version Number

5.1.1

Codesandbox/Expo snack

https://codesandbox.io/p/devbox/eager-sun-jt4df-82ptws

Steps to reproduce

1. open the console in the preview
2. Submit the form
3. See error
4. to make the error goes array, uncomment the line 56

When using Zod resolver and nested discriminated unions, the resolver is not validating the required field before trying to execute the nested discriminated union validations, leaving the error message below:

Uncaught TypeError: Cannot read properties of undefined (reading '0')

Using the @hookform/resolvers/standard-schema works as expected. It validates if the nested discriminated field is filled before going to its validation. But the errors type returns blank as shown in the print below (not sure if this is another bug or expected), and I use it to have a custom map error (z.setErrorMap).

Expected behaviour

work as the parent/root discriminatedUnion, returning the error type invalid_union_discriminator for the field when is not selected

What browsers are you seeing the problem on?

Chrome

Relevant log output

Uncaught TypeError: Cannot read properties of undefined (reading '0')

Code of Conduct

• I agree to follow this project's Code of Conduct

[cascornelissen]

I'm running into this as well and noticed the fix in #784 solves the issue for me.

[willisplummer-patreon]

#784 fixed for me. I think this issue can probably be closed. Thanks!