Zod & env-schema Validation

import { z } from "zod";
 
const envSchema = z.object({
  NODE_ENV: z.enum(["development", "test", "production"]),
  PORT: z.coerce.number().int().min(1).max(65535).default(3000),
  DATABASE_URL: z.string().url(),
  JWT_SECRET: z.string().min(32),
});
 
export type Env = z.infer<typeof envSchema>;
export const env = envSchema.parse(process.env);

# CI: validate example env file
npx tsx -e "import { envSchema } from './src/env'; envSchema.parse(require('dotenv').config({path:'.env.example'}).parsed)"

// src/env.ts
import { z } from "zod";
 
const envSchema = z
  .object({
    NODE_ENV: z.enum(["development", "test", "production"]),
    PORT: z.coerce.number().default(3000),
    DATABASE_URL: z.string().url(),
    REDIS_URL: z.string().url().optional(),
    CACHE_TTL_SECONDS: z.coerce.number().positive().default(300),
    STRIPE_SECRET_KEY: z.string().startsWith("sk_"),
    LOG_LEVEL: z.enum(["debug", "info", "warn", "error"]).default("info"),
    OTEL_EXPORTER_OTLP_ENDPOINT: z.string().url().optional(),
  })
  .refine(
    (e) => e.NODE_ENV !== "production" || e.OTEL_EXPORTER_OTLP_ENDPOINT,
    { message: "OTEL_EXPORTER_OTLP_ENDPOINT required in production", path: ["OTEL_EXPORTER_OTLP_ENDPOINT"] }
  );
 
export type Env = z.infer<typeof envSchema>;
 
function formatZodError(error: z.ZodError): string {
  return error.issues.map((i) => `${i.path.join(".")}: ${i.message}`).join("\n");
}
 
export function loadEnv(source: NodeJS.ProcessEnv = process.env): Env {
  const result = envSchema.safeParse(source);
  if (!result.success) {
    console.error("Invalid environment configuration:\n" + formatZodError(result.error));
    process.exit(1);
  }
  return result.data;
}
 
export const env = loadEnv();
 
// src/main.ts
import { env } from "./env";
import express from "express";
 
const app = express();
app.get("/health", (_req, res) => res.json({ ok: true, env: env.NODE_ENV }));
app.listen(env.PORT);

// JSON config blob in one env var (use sparingly)
const featureFlagsSchema = z
  .string()
  .default("{}")
  .transform((s, ctx) => {
    try {
      return JSON.parse(s) as Record<string, boolean>;
    } catch {
      ctx.addIssue({ code: "custom", message: "FEATURE_FLAGS_JSON must be valid JSON" });
      return z.NEVER;
    }
  });

// Pass Env into factories - never pass whole process.env
export function createDbPool(cfg: Pick<Env, "DATABASE_URL">) {
  return new Pool({ connectionString: cfg.DATABASE_URL });
}