Environment variables validation script

validate-env.ts

import fs from 'fs';
import dotenv from 'dotenv';

type ValidationErorr = {
  property: string;
  message: string;
};

class ValidationError extends Error {}

const optionalKeys = ['PORT'];

const main = () => {
  if (process.argv.length !== 3) {
    throw new Error('Arguments length must be 3.');
  }

  const envFilename = process.argv[2];

  const envFileString = fs.readFileSync(envFilename, { encoding: 'utf-8' });
  const envData = dotenv.parse(envFileString);

  const sampleEnvFileString = fs.readFileSync('.env.sample', { encoding: 'utf-8' });
  const sampleEnvData = dotenv.parse(sampleEnvFileString);

  const errors: ValidationErorr[] = [];

  Object.keys(sampleEnvData).forEach((envKey) => {
    const envValue = envData[envKey];

    if (!(envKey in envData) && !optionalKeys.includes(envKey)) {
      errors.push({ property: envKey, message: `${envKey} is missing.` });
    } else if (envValue?.trim() === '') {
      errors.push({ property: envKey, message: `${envKey} must have a value.` });
    }
  });

  if (errors.length > 0) {
    throw new ValidationError(JSON.stringify(errors, null, 2));
  }

  console.log('Successfully validated the environment variables!');
};

main();