envsyncer/src/sync.ts

Sync your root .env files into monorepo subfolders with ease

import fs from 'fs';
import path from 'path';
import chalk from 'chalk';

const ENV_FILES = ['.env', '.env.local', '.env.development', '.env.production'];

function parseEnvVars(content: string): Set<string> {
  const envVars = new Set<string>();
  const lines = content.split('\n');
  
  for (const line of lines) {
    const trimmed = line.trim();
    // Skip comments and empty lines
    if (trimmed && !trimmed.startsWith('#')) {
      const equalIndex = trimmed.indexOf('=');
      if (equalIndex > 0) {
        const varName = trimmed.substring(0, equalIndex);
        envVars.add(varName);
      }
    }
  }
  
  return envVars;
}

function extractLocalEnvVars(localContent: string, rootEnvVars: Set<string>): string[] {
  const lines = localContent.split('\n');
  const localEnvLines: string[] = [];
  
  for (const line of lines) {
    const trimmed = line.trim();
    
    // Keep comments and empty lines that are not at the start
    if (!trimmed || trimmed.startsWith('#')) {
      // Only keep local comments if they're not environment variable comments
      if (localEnvLines.length > 0) {
        localEnvLines.push(line);
      }
      continue;
    }
    
    const equalIndex = trimmed.indexOf('=');
    if (equalIndex > 0) {
      const varName = trimmed.substring(0, equalIndex);
      // Only keep local env vars that are not in root
      if (!rootEnvVars.has(varName)) {
        localEnvLines.push(line);
      }
    }
  }
  
  // Remove trailing empty lines
  while (localEnvLines.length > 0 && !localEnvLines[localEnvLines.length - 1].trim()) {
    localEnvLines.pop();
  }
  
  return localEnvLines;
}

export async function syncEnvToTargets(targetDirs: string[]) {
  const rootEnvFiles = ENV_FILES.filter((file) =>
    fs.existsSync(path.join(process.cwd(), file))
  );

  if (rootEnvFiles.length === 0) {
    console.log(chalk.red('❌ No .env files found in root directory.'));
    console.log(
      chalk.gray('Looked for:', ENV_FILES.join(', '))
    );
    return;
  }

  console.log(chalk.blue('\n📄 Found env files:'), rootEnvFiles.join(', '));

  for (const envFile of rootEnvFiles) {
    const rootEnvPath = path.join(process.cwd(), envFile);
    const rootEnvContent = fs.readFileSync(rootEnvPath, 'utf-8');
    const rootEnvVars = parseEnvVars(rootEnvContent);

    for (const dir of targetDirs) {
      const targetPath = path.join(process.cwd(), dir, envFile);
      
      try {
        let localEnvLines: string[] = [];
        
        // Backup local env vars if the file exists
        if (fs.existsSync(targetPath)) {
          const localEnvContent = fs.readFileSync(targetPath, 'utf-8');
          localEnvLines = extractLocalEnvVars(localEnvContent, rootEnvVars);
        }
        
        // Start with root env content (preserves all formatting and comments)
        let finalContent = rootEnvContent;
        
        // Add local env vars if any exist
        if (localEnvLines.length > 0) {
          // Ensure root content ends with a newline
          if (!finalContent.endsWith('\n')) {
            finalContent += '\n';
          }
          
          // Add separator comment
          finalContent += '\n# Local environment variables\n';
          finalContent += localEnvLines.join('\n');
          
          // Ensure final content ends with a newline
          if (!finalContent.endsWith('\n')) {
            finalContent += '\n';
          }
        }
        
        fs.writeFileSync(targetPath, finalContent);
        
        const localCount = localEnvLines.filter(line => line.trim() && !line.trim().startsWith('#')).length;
        const message = localCount > 0 
          ? `✅ Synced ${envFile} to ${chalk.gray(`${dir}/${envFile}`)} ${chalk.cyan(`(preserved ${localCount} local vars)`)}`
          : `✅ Synced ${envFile} to ${chalk.gray(`${dir}/${envFile}`)}`;
        
        console.log(chalk.green(message));
      } catch (error) {
        console.error(
          chalk.red(`❌ Failed to sync ${envFile} to ${dir}:`),
          error
        );
      }
    }
  }
}