zod env validation

env.ts

// config/env.ts
import assert from "utils/assert"
import * as z from "zod"

assert(typeof window === "undefined", 
       "The config/env.ts file cannot be used in the browser")

const isProduction = process.env.NODE_ENV === "production"
const isDevelopment = process.env.NODE_ENV === "development"
const isTest = process.env.NODE_ENV === "test"

// -------------------
// Base env schema
// -------------------
const baseSchema = z
  .object({
    production: z.boolean(),
    development: z.boolean(),
    test: z.boolean(),
    APP_ORIGIN: z.string(),
  })
  .nonstrict()

// ----------------------
// Production env schema
// ----------------------
let productionEnvSchema = z.object({
  VERCEL_URL: z.string(),
  SENDGRID_API_KEY: z.string(),
})

let envSchema
if (isProduction) {
  envSchema = baseSchema.merge(productionEnvSchema)
} else {
  envSchema = baseSchema.merge(productionEnvSchema.partial())
}

export const env = envSchema.parse({
  ...process.env,
  production: isProduction,
  development: isDevelopment,
  test: isTest,
  APP_ORIGIN: isProduction ? process.env.VERCEL_URL : "http://localhost:3000",
})


// --------------------------------------------
// --------------------------------------------
// --------------------------------------------
// And then use it like this:
import {env} from 'config/env'

if (env.production) {
  // stuff
}

env.APP_ORIGIN       // Guaranteed to be defined
env.SENDGRID_API_KEY // Guaranteed to be defined in production

// Photo by Alex Beaz on Unsplash