@olegjs/on-change/on-change.js

Run a command when a file changes since last time the command was executed

#!/usr/bin/env node

const { yellow, magenta } = require('chalk')
const { spawnSync } = require('child_process')
const { existsSync, readFileSync, writeFileSync } = require('fs')

const {
  checksum,
  checksumFilePath: getChecksumFilePath,
  hashFromFileContent,
} = require('./checksum')

const argv = require('yargs')
  .scriptName('on-file-change')
  .usage('Usage: $0 --file [file] [command]')
  .example(
    '$0 --file package-lock.json npm ci',
    'Reinstall dependencies on changed package-lock.json',
  )
  .option('file', {
    alias: 'f',
    demandOption: true,
    describe: 'Path to file to check for changes',
    type: 'string',
  })
  .demandCommand(1).argv

const UTF = 'utf8'

const getPastCheckSum = path =>
  existsSync(path) ? hashFromFileContent(readFileSync(path, UTF)) : null

const checkSum = checksum(readFileSync(argv.file, UTF))
const checksumFilePath = getChecksumFilePath(argv.file)
const pastCheckSum = getPastCheckSum(checksumFilePath)

if (checkSum !== pastCheckSum) {
  console.log(
    `File "${magenta(argv.file)}" has changed.`,
    `Running "${yellow(argv._.join(' '))}"...`,
  )

  const [command, ...args] = argv._
  spawnSync(command, args, { encoding: UTF, stdio: 'inherit' })
  writeFileSync(checksumFilePath, `${checkSum}  ${argv.file}`)
}