Attach new global string validation functions directly to z.string()

[jgoux]

Hello all,

Is it possible to extend z.string() to add other string validation functions in the vein as the built-in uuid and email functions? Something like z.string().iban().

This would be very handy for validations that are common across the codebase and to handle i18n on the error message. I know I could use refinement but it's not convenient for often used validation rules.

I made a special ErrorMap for i18next and it would automatically be handled by this case : https://gist.github.com/jgoux/720f011a4428e64f50bebc9938219518#file-zod-ts-L60-L68

I'm currently using the v3 in alpha. 😄

[colinhacks]

The best part (in my opinion) of v3 is that anyone can define their own schema classes by simply subclassing ZodType. In your case, you could directly subclass ZodString and add these methods yourself. It wouldn't be super difficult, just look at the ZodString implementation to see how it works.

Besides iban what methods are you looking to add? I might be amenable to adding them to core. I'm a little surprised I don't get more requests for other string validation methods.

Alternatively consider using the "re-export pattern".

// customzod.ts;
export * from 'zod';
export const iban = ()=>z.string().refine(validateIban, { message: "Invalid IBAN" });

// server.ts
import * from "./customzod";

z.object({
  iban: z.iban()
})

That custom error map looks really great! If you think that would be useful for other people, consider publishing it to NPM and I'll link to it on the README.

[jgoux]

I didn't realized you could pass ErrorMap to parse! This is awesome and totally solve my double z issue! 💯💯💯

Noted for the re-export pattern, I'll use the "string" version instead which is more like I wanted.

Thanks for the tips Colin. ☺️

[colinhacks]

You bet!

[DominikSerafin]

@colinhacks I've read multiple issues, PRs and discussions here in this repo, and somehow I still can't come up with a solution to simply create a new custom validation method for primitives that is chainable (in Zod v3).

What I'm basically trying to achieve is to be able to write something like this:

import * as z from './zod-extended';

const schema = z.object({
  text: z.string().min(5).nonewlines().max(200),
});
const parsed = schema.parse({text: 'example'});

This example has nonewlines() method chained between other string methods (which should throw an error if string has any newline characters).

This is just an example, though, as I'd want to find a way to add a custom validation methods (with custom error code & message) for some of the other primitive types as well (string, number, bigint, date).

The re-export pattern doesn't let me chain my custom method. And I've tried the subclass approach, but I wasn't able to figure out how to do that properly (I've looked into ZodString implementation, like you've suggested).

I would really appreciate your help.

[colinhacks]

Here's a simple example of implementing a subclass of ZodString. As long as all your methods delegate to .refine and .transform, this is fairly straightforward.

class CustomString extends z.ZodString {
  toNumber() {
    return this.transform((val) => val.length);
  }

  static create = (): CustomString => {
    return new CustomString({
      checks: [],
    });
  };
}

const mySchema = CustomString.create().toNumber();

If you want to modify the parsing logic, add additional state/properties, etc, things get more complicated. You'll just have to bite the bullet and learn how the existing schema types work.

[DominikSerafin]

@colinhacks thanks for the reply! I've moved this discussion to #516 (so it's a bit cleaner)