Environment configuration in Nest.js

Author: Dawid Motak

Problem context

In application, we were using ConfigService class that was a singleton used as a wrapper around process.env.

@Injectable()
export class ConfigService {
  static loadConfig() {
    const configInstance = new ConfigService();
    if (process.env.NODE_ENV === "test") {
      dotenv.config({ path: `${process.cwd()}/.env.test` });
    } else {
      dotenv.config();
    }
    return configInstance;
  }

  public static get(env: ConfigType): any {
    return process.env[env];
  }
}

@Global()
@Module({
  providers: [
    {
      provide: ConfigService,
      useFactory: () => ConfigService.loadConfig(),
    },
  ],
  exports: [ConfigService],
})
export class ConfigModule {}

There were two main problems with this approach:

• lack of typing for environment variables
• lack of validation for environment variables