installPackages.js

const Path = require('path')
const FS = require('fs-extra')
const Spawn = require('cross-spawn')
const { resolve, coroutine, runNode } = require('creed')

const accessibleFile = (path) => runNode(FS.access, path).map(() => path).catch(() => null)

const installPackages = coroutine(function * installPackage(projectPath, packageNames, { dev = false, useYarn = false } = {}) {
	const appPackage = yield FS.readJSON(Path.join(projectPath, 'package.json'))
	const dependencies = (dev ? appPackage.devDependencies : appPackage.dependencies) || {}
	const needInstalling = packageNames.filter(packageName => !dependencies[packageName])
	if (needInstalling.length === 0) {
		return
	}

	useYarn = !!(yield accessibleFile(Path.join(projectPath, 'yarn.lock'))) || useYarn
	const command = useYarn ? 'yarnpkg' : 'npm'
	let args = useYarn ? ['add'].concat(dev ? ['--dev'] : []) : ['install', dev ? '--save' : '--save-dev']
	args.push.apply(args, needInstalling)
	const proc = Spawn.sync(command, args, {
		cwd: projectPath,
		stdio: 'inherit'
	})
	if (proc.status !== 0) {
	  throw new Error(`\`${command} ${args.join(' ')}\` failed with status ${proc.status}`)
	}
})

module.exports = installPackages