run 'npm install' if package.json was modified

runNpmIfPackageUpdated.js

const util = require('util')
const childProcess = require('child_process')
const exec = util.promisify(childProcess.exec)

async function main() {
  try {
    const { stdout: changeFiles } = await exec(
      'git diff-tree -r --name-only --no-commit-id ORIG_HEAD HEAD'
    )
    if (changeFiles.includes('package.json')) {
      console.log(`# package.json update, so run 'npm install' #\n`)
      await runNpmInstall()
    }
  } catch (err) {
    console.error(`# Failed to get diff info/ run 'npm install' `)
    console.error(`# error message:
--------------------->
${err.message}
<--------------------`)
    process.exit()
  }
}

function runNpmInstall() {
  return new Promise((resolve, reject) => {
    const npmInstall = childProcess.spawn(
      process.platform === 'win32' ? 'npm.cmd' : 'npm',
      ['install'],
      {
        stdio: 'inherit'
      }
    )

    npmInstall.on('exit', (code, signal) => {
      resolve()
    })
    npmInstall.on('error', err => {
      reject(err)
    })
  })
}

main()