Change refined z.string's errorMap after construction

[rijenkii]

Say I have a complex string schema with a lot of transformations and refines, and its definition is unknown to me so I cannot just copy it.

How can I change the errorMap of that schema? Editing schema._def.errorMap does not seem to work:

const field = z.string().refine(() => true);
field._def.errorMap = () => ({ message: "custom error" });
const obj = z.object({ field });
obj.safeParse({});
// Uncaught ZodError: [
//   {
//     "code": "invalid_type",
//     "expected": "string",
//     "received": "undefined",
//     "path": [
//       "field"
//     ],
//     "message": "Required"
//   }
// ]