.superRefine

.superRefine() runs custom validation after the value has been parsed and gives the callback a context for adding validation issues. Unlike .refine(), it can emit multiple issues and use Zod's internal issue types, while a type-predicate callback can narrow the inferred type.

schema.superRefine((value, ctx) => { ctx.addIssue({ code: "custom", message: "Invalid value" }); })

A new schema with the added refinement logic.

import { z } from "zod";

const UniqueStringArray = z.array(z.string()).superRefine((value, ctx) => {
  if (value.length > 3) {
    ctx.addIssue({
      code: "too_big",
      maximum: 3,
      origin: "array",
      inclusive: true,
      message: "Too many items",
      input: value,
    });
  }

  if (value.length !== new Set(value).size) {
    ctx.addIssue({
      code: "custom",
      message: "No duplicates allowed",
      input: value,
    });
  }
});

UniqueStringArray.parse(["a", "a", "b", "c"]);

This schema reports separate issues for exceeding the length limit and for duplicate values.