index.js

#!/usr/bin/env node
const { glob } = require('glob')
const { 
    statSync,
    writeFileSync,
    readFileSync,
    existsSync
} = require('fs')

const { Command } = require('commander')
const { version } = require('./package.json')
const { spawn } = require('child_process')


const program = new Command()
program.version(version)
    .name('rim')
    .allowUnknownOption()
    .option('-m, --minimatch <match>', 'Files scanned for changes', 'src/**/*.{tsx,ts,jsx,js,svg,html,css,scss,less}')
    .option('-s, --snapshot <file>', 'Snapshot files', '.run-on-diff.cache.json')
    .usage('-s \'.cache\' -m \'**/*.svg\' echo "hello world on change"')

program.parse(process.argv)

function isEqual(a, b) {
    const ak = Object.keys(a)
    const bk = Object.keys(b)
    if (ak.length !== bk.length) return false
    for (const i of ak) if (a[i] !== b[i]) return false
    for (const i of bk) if (a[i] !== b[i]) return false
    return true
}

const snapshot = Object.assign({}, ...glob.sync(program.minimatch)
    .map((file) => ({ [file]: statSync(file).mtime.getTime() })))

if (existsSync(program.snapshot)) {
    const oldSnapshot = JSON.parse(readFileSync(program.snapshot).toString())
    if (isEqual(oldSnapshot, snapshot)) return
}

const arguments = [...program.args]
const command = arguments.shift()
if (!command) process.exit(0)
const child = spawn(command, arguments)
process.stdin.pipe(child.stdin)
child.stdout.pipe(process.stdout)
child.stderr.pipe(process.stderr)
child.on('exit', (e) => {
    if (e === 0) writeFileSync(program.snapshot, JSON.stringify(snapshot))        
    process.exit(e)
})