zod.function as property of zod.object loses this

[ddurschlag]

Quoting myself from discord:

const MyObj = z.object({ foo: z.function() });
class MyObjImpl implements z.infer<typeof MyObj> { private bar: string; constructor(){this.bar = 'baz';} foo() { console.log(this.bar); } };
const inst = MyObj.parse(new MyObjImpl()); //ok
inst.foo(); // kablooey :( "this is undefined"

The problem is that the parsed object's parsed method is an arrow function, and thus has a "this" of the ZodFunction (see:

zod/src/types.ts

Line 3755 in 1ecd624

return OK((...args: any[]) => {

). A similar problem applies to async functions.

I can think of two possible solutions here. First is to make the parsed result a normal function instead of an arrow function, then apply its this to the underlying fn. The second is to use proxies on either the parsed function, the parsed object, or both to get a similar behavior.

I'll have a not-yet-mergeable PR for the former strategy up for this shortly. Would love help getting it over the line.