build.js

// this whole thing is a really fragile hack
// but it works so ¯\_(ツ)_/¯

const stylisPath = require.resolve('stylis')
const { promisify } = require('util')
const j = require('jscodeshift')
const request = require('request-promise-native')
const fs = require('fs')
const babylon = require('babylon')
const prettier = require('prettier')

const readFile = promisify(fs.readFile)
const writeFile = promisify(fs.writeFile)

const removeOptions = src =>
  j(src)
    .find(j.SwitchStatement)
    .forEach(thing => {
      thing.value.cases = thing.value.cases.filter(node => {
        if (!node.test) return true
        switch (node.test.value) {
          case 'keyframe':
          case 'cascade':
          case 'preserve':
          case 'semicolon':
          case 'compress':
          case 'global': {
            return false
          }
          default: {
            return true
          }
        }
      })
    })
    .toSource()

const setOptions = src =>
  j(src)
    .find(j.VariableDeclarator)
    .forEach(path => {
      switch (path.value.id.name) {
        case 'escape':
        case 'keyed': {
          path.value.init.value = 0
          return
        }
        case 'semicolon': {
          path.value.init.value = 1
        }
      }
    })
    .toSource()

const removeUMDWrapper = src =>
  j(src)
    .find(j.Program)
    .forEach(thing => {
      delete thing.value.body[1]
    })
    .toSource()

async function doThing() {
  const stylisSrc = (await readFile(stylisPath))
    .toString()
    .replace(
      'cascade + quote + bracket + atrule === 0 && id !== KEYFRAME && code !== SEMICOLON',
      'true === false'
    )
    .replace(
      'comment + quote + parentheses + bracket + semicolon === 0',
      'true === false'
    )
    .replace('(insert === 1)', '(true === false)')
    .replace('input.charCodeAt(9)*keyed', '0')
    .replace('switch (cascade + level) {', 'switch (2) {')
    .replace('compress*code === 0', 'true')
    .replace(`typeof(output = result) !== 'string'`, 'output = result')
  const result = setOptions(removeOptions(stylisSrc))

  // await writeFile('./src/stylis.js', result)
  console.log('start request')
  const data = (await request('https://closure-compiler.appspot.com/compile', {
    method: 'POST',
    form: {
      js_code: result,
      compilation_level: 'ADVANCED_OPTIMIZATIONS',
      output_format: 'text',
      output_info: 'compiled_code'
    }
  })).toString()
  const srcWithoutUMDWrapper = removeUMDWrapper(data)
  const finalSrc =
    srcWithoutUMDWrapper +
    '\nexport default ' +
    babylon.parse(srcWithoutUMDWrapper).program.body[0].declarations[0].id.name
  await writeFile('./src/stylis.min.js', prettier.format(finalSrc))

  console.log('done')
}

doThing()