Wrong type inference when using Zod

Question

In this validation schema, if the validation passes, the type of email will always be a string. However, for some reason typescript is telling me that email either returns a string or false. I do not see any possibility that email could ever return false, am I missing something?

To elaborate: When I use z.string().email(), I am guaranteeing that the outcome is indeed a valid email, otherwise the validation will fail and the value will not be passed to the transform > normalizeEmail part. So the final result must indeed be an string.

import { z } from "zod";
import validator from "validator";

const email = (maxChar: number) =>
  z
    .string()
    .max(maxChar)
    .email().transform((value) => validator.normalizeEmail(value))
    ;

Answer 1

validator.normalizeEmail returns false if the email is not valid (which is a strange design choice if you ask me). Since you are already checking if it is a valid email using Zod, I would opt for an assertion:

const email = (maxChar: number) =>
  z
    .string()
    .max(maxChar)
    .email().transform((value) => validator.normalizeEmail(value) as string)
    ;

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