Zod JSON Coercion

z-json.ts

import * as z from 'zod'

function zJson <T extends z.ZodTypeAny> (schema: T) {
  return z.string().transform((val, ctx) => {
    try {
      return JSON.parse(val)
    } catch (err) {
      ctx.addIssue({
        code: z.ZodIssueCode.custom,
        message: 'Invalid JSON',
      })
      return z.NEVER
    }
  }).pipe(schema)
}

// example
const env = z.object({
  // Should be a json string that parses to an array of string urls
  WEBHOOK_URLS: zJson(z.array(z.string().url()))
})