feature request: zod.fallback() and zod.catch()

zod is awesome!

Maybe this is already possible, but often I need more granular control of safeParse-like behavior… Something like:

const color = string().fallback('#000000');
const person = object({ name: string(), age: number() }).fallback({});

Or, maybe with more granular control (e.g. have the fallback be based on a ZodError):

const person = object( {name: string(), age: number() }.catch(err =>  { console.error(err.message); return {} );

(so .fallback(foo) is just .catch(() => foo)).

Thanks for listening/considering!

ps: some of this might be doable with any().transform(val => xxx).string() but seems super hacky and non zod-like since you basically have to use JS/TS to coerce the value…

[ehahn9]

In case anyone comes across this in the future, here’s an even better (IMHO) approach which does not involve safeParse etc.:

import { any } from 'zod';

/**
 * Create a schema matches anything and returns a value. Use it with `or`:
 *
 * const schema = zod.number();
 * const tolerant = schema.or(fallback(-1));
 *
 * schema.parse('foo')      // => ZodError
 * tolerant.parse('foo')    // -1
 */
export function fallback<T>(value: T) {
  return any().transform(() => value);
}

[ehahn9]

Awesome @colinhacks. Totally agree about keeping out of core… Feel free to close this whenever you like!

Just to clarify my OP, the fallback value isn’t always compatible with Schema<T>. I’ve found this idiom most useful when I want to read an array of values (e.g. firestore records) but be tolerant of bad values:

// get some things, ignoring the invalid entries:
const things = zod.array(fallback(thingSchema, false))
const goodThings = compact(things)