RFC: Make object schemas nonstrict by default

Zod’s policy of disallowing any unknown keys by default is confusing and probably not worth it. It also makes the inferred types incorrect:

const A = z.object({
  a: z.string(),
});

const B = z.object({
  b: z.string(),
});

const AB = z.intersection(A, B);


type AB = z.infer<typeof Teacher>;
// { a: string; b: string };

The actual inferred type here should be never because no data will properly pass validation.

If anyone has a reason why object schemas should be strict by default, speak now!

[chrbala]

The primary thing I care about regarding this issue is that there’s a path to getting a clean object without erroneous keys. If you use zod to validate before a schemaless database, you might find out you have a bunch of unwanted fields if there aren’t good protections in place. Perhaps making this explicit like a ZodSchema.parse(val, { clean: true }) which would allow for this.

Even right now, this is a bit cumbersome because unused fields have to be manually removed. A value cleaner would make this nicer.

[chrbala]

If object schemas become nonstrict by default (which generally makes sense to me), how would parsing work? I see some advantages in being able to give an object with extra keys, then parsing removes them.

const Obj = z.object({
  key: z.string(),
});

Obj.parse({key: 'value', key2: 'value2'})  // could return { key: 'value' }