Validating NestJS env vars with Zod

Hey there! If you're like me, you probably love using Zod for validating and parsing data objects. It's a lifesaver, right? But when it comes to environment variables (env vars), things can get a bit tricky. You want to parse them as quickly as possible during your application's boot-up phase and then use them confidently throughout your app. That's where NestJS's ConfigModule comes into play.

Setting Up ConfigModule

NestJS provides a handy ConfigModule that lets you register a global module to read your env file and load it into the process. But here's the catch: you need to validate those env vars to ensure they're correct. Luckily, the ConfigModule allows you to register a validate function. Here's a quick look at how you can set it up:

import { ConfigModule } from '@nestjs/config';
 
@Module({
  imports: [
    ConfigModule.forRoot({ isGlobal: true, validate: /* Your function */ }),
  ]
})
export class AppModule {}

Validating with Zod

The validate function receives the full process.env object and expects a validated, parsed object in return. This is where Zod comes in handy. You can use it to format and validate your env vars like this:

import { z } from "zod";