should-use-yarn.ts

import { execSync } from 'child_process'
import fs from 'fs'
import path from 'path'

export function shouldUseYarn(baseDir: string): boolean {
  try {
    const userAgent = process.env.npm_config_user_agent
    if (userAgent) {
      return Boolean(userAgent && userAgent.startsWith('yarn'))
    } else {
      if (fs.existsSync(path.join(baseDir, 'yarn.lock'))) {
        return true
      } else if (fs.existsSync(path.join(baseDir, 'package-lock.json'))) {
        return false
      }
      execSync('yarnpkg --version', { stdio: 'ignore' })
      return true
    }
  } catch (e) {
    return false
  }
}