Validating .env Files

A common challenge when working with environment variables is ensuring that all required variables are present in your .env file. With envoyage, you can easily check for missing or extra variables.

The Pattern

Let's say you have a "local" environment that uses the "from-env" resolution to read variables from a .env file:

const envReg = createEnvironmentRegistry()
  .addEnv("local", /* ... */, (e) => e
    .addResolution("from-env", /* ... */))
  .addEnv(/* ... */)

You can validate your .env file by comparing the variables defined in your code against those present in the .env file:

import * as fs from "fs/promises"
import * as dotenv from "dotenv"

// Function to validate .env file
const validateEnv = async function () {
  // Get all variables that use "from-env" in the local environment
  const requiredVars = varReg.listVariables("local", "from-env")
  
  // Read actual variables from .env file
  const envContent = await fs.readFile(".env", "utf-8")
  const actualVars = Object.keys(dotenv.parse(envContent))
  
  // Find missing and extra variables
  const missingVars = requiredVars.filter(v => !actualVars.includes(v))
  const extraVars = actualVars.filter(v => !requiredVars.includes(v))
  
  // Report validation results
  if (missingVars.length > 0) {
    console.error("❌ Missing required variables in .env:")
    missingVars.forEach(v => console.error(`  - ${v}`))
    process.exit(1)
  }
  
  if (extraVars.length > 0) {
    console.warn("⚠️  Extra variables found in .env:")
    extraVars.forEach(v => console.warn(`  - ${v}`))
  }
  
  if (missingVars.length === 0) {
    console.log("✅ All required variables are present in .env")
  }
}

You can run this validation when your application starts or as part of your development workflow.