Zod Unique Array

zod-unique-array.ts

/** Array where are elements are expected to be unique by a custom key */
export function zUniqueArray<
  ArrSchema extends z.ZodArray<z.ZodTypeAny, 'many'>,
  UniqueVal,
>(
  uniqueBy: (item: z.infer<ArrSchema>[number]) => UniqueVal,
  schema: ArrSchema,
) {
  return schema.superRefine((items, ctx) => {
    const seen = new Set<UniqueVal>()
    for (const [i, item] of items.entries()) {
      const val = uniqueBy(item)
      if (seen.has(val)) {
        ctx.addIssue({
          code: z.ZodIssueCode.custom,
          message: `Unique property validation failed`,
          path: [i],
        })
      } else {
        seen.add(val)
      }
    }
  })
}