Validate multiple fields against each other using Zod

It’s common to validate fields based on other fields. For example, a form with a start date and end date.

The way to do this with Zod (that I know of) is like the snippet below. However, typescript will complain because validator will only accept a schema of type ZodObject, whereas here the schema is of type ZodEffects.

export const schema = z
	.object({
		start: z.date(),
		end: z.date(),
	})
	.refine((val) => val.start < val.end, {
		path: ['start'],
		message: 'Start date must be before end date',
	})
	.refine((val) => val.start < val.end, {
		path: ['end'],
		message: 'End date must be after start date',
	});

const { form } = createForm({
  // ...
  validate: validateSchema(schema)
  // ...
});

I’ve had some success with manually casting like below. It doesn’t seem to work all the time though. Some of my forms fail to validate properly even when doing this. Not sure why yet.

-		validate: validateSchema(schema),
+		validate: validateSchema(schema as z.AnyZodObject),