Reusable functions: internal PR for clarity

[bahmutov]

Factor out reusable functions

• see example use in https://github.com/cypress-io/github-action/blob/master/index.js

Typical use

const { restoreCache, saveCache } = require('cache/lib/index')
const hasha = require('hasha')

// let's cache NPM modules ~/.npm
const packageLockHash = hasha.fromFileSync('./package-lock.json')
const platformAndArch = `${process.platform}-${process.arch}`

const NPM_CACHE = (() => {
  const o = {
    inputPath: '~/.npm',
    restoreKeys: `npm-${platformAndArch}-`
  }
  o.primaryKey = o.restoreKeys + packageLockHash
  return o
})()

const restoreCachedNpm = () => {
  console.log('trying to restore cached NPM modules')
  return restoreCache(
    NPM_CACHE.inputPath,
    NPM_CACHE.primaryKey,
    NPM_CACHE.restoreKeys
  )
}

const saveCachedNpm = () => {
  console.log('saving NPM modules')
  return saveCache(NPM_CACHE.inputPath, NPM_CACHE.primaryKey)
}

Note

• ignore lib files - these are just transpiled from src to allow us directly installing this module from GitHub using a tag without going through NPM