Discriminated union + useFieldArray + error messages

[meckanism]

I'm trying to access the error messages per field but since i'm using a descriminated union i'm having a tough time narrowing it.

const formSchema = z.object({
  editChanges: z.array(
    z.discriminatedUnion("action", [
      z.object({
        id: z.number(),
        action: z.literal(EditActions.DELETE_GROUP),
        data: z.object({
          id: z.number(),
          groupName: z.string(),
        }),
      }),
      z.object({
        id: z.number(),
        action: z.literal(EditActions.RENAME_GROUP),
        data: z
          .object({
            id: z.number(),
            oldGroupName: z.string(),
            newGroupName: z.string(),
          })
          .superRefine((data, ctx) => {
            const newName = data.newGroupName.trim();
            const oldName = data.oldGroupName.trim();

            if (oldName === newName) {
              ctx.addIssue({
                code: "custom",
                message: "Group name cannot be the same",
                path: ["newGroupName"],
              });
            }
          }),
      }),
    ])
  ),
});

When i try to get the error messages i'm not getting the correct shape on data because I have no way to descriminate against 'action'

const errorMessage =
            errors.editChanges?.[index]?.data?.newGroupName?.message;
                                                                                      ^
Property 'newGroupName' does not exist on type 'Merge<FieldError, FieldErrorsImpl<{ id: number; groupName: string; }>> | Merge<FieldError, FieldErrorsImpl<{ id: number; oldGroupName: string; newGroupName: string; }>>'.
  Property 'newGroupName' does not exist on type 'Merge<FieldError, FieldErrorsImpl<{ id: number; groupName: string; }>>'.

Any help/hint is appreciated. Repro is here https://codesandbox.io/p/sandbox/f8rn68

[BrendanC23]

How about this? See the CodeSandbox.

const errorData = errors.editChanges?.[index]?.data;

console.log(errorData);

const errorMessage =
    errorData && "newGroupName" in errorData
      ? errorData.newGroupName?.message
      : false;

[meckanism]

Guess there was a way to narrow, thanks =)