rollup.config.js

import * as fs from 'fs'
import * as path from 'path'
import alias from 'rollup-plugin-alias'
import babelMinify from 'rollup-plugin-babel-minify'
import nodeResolve from 'rollup-plugin-node-resolve'
import replace from 'rollup-plugin-replace'
import typescript from 'rollup-plugin-typescript'
import rollupVisualizer from 'rollup-plugin-visualizer'
import license from 'rollup-plugin-license'
import * as pkg from './package.json'

const { LERNA_PACKAGE_NAME, LERNA_ROOT_PATH } = process.env
const PACKAGE_ROOT_PATH = path.join(LERNA_ROOT_PATH, 'packages', LERNA_PACKAGE_NAME)
const IS_BROWSER_BUNDLE = LERNA_PACKAGE_NAME === 'tko'
const INPUT_FILE = path.join(PACKAGE_ROOT_PATH, 'src/index.js')
const TKO_MODULES = getTkoModules()

const banner = `/*!
 * <%= pkg.description %> 🥊  <%= pkg.name %>@${pkg.version}
 * (c) The Knockout.js Team - ${pkg.homepage}
 * License: ${pkg.licenses[0].type} (${pkg.licenses[0].url})
 */
`

  /* Use TypeScript instead of babel for transpilation for IE6 compat, plus it's faster */
const TYPESCRIPT_CONFIG = {
  include: '**/*.js',
  exclude: 'node_modules',
  typescript: require('typescript')
}

/* Plugins used for all builds */
const UNIVERSAL_PLUGINS = [
  /* Replace {{VERSION}} with pkg.json's `version` */
  replace({ delimiters: ['{{', '}}'], VERSION: pkg.version }),
  nodeResolve({ module: true }),
  rollupVisualizer({ filename: 'visual.html' }),
  license({ sourceMap: true, banner })
]

export default [
  /* tko.<module?>.es6.js */
  createRollupConfig(),
  /* tko.<module?>.js */
  createRollupConfig({ transpile: true }),
  ...(IS_BROWSER_BUNDLE
    ? [
      /* tko.es6.min.js */
      createRollupConfig({ minify: true }),
      /* tko.min.js */
      createRollupConfig({ minify: true, transpile: true })
    ]
    : []
  )
]

function getTkoModules () {
  return fs.readdirSync(path.resolve(__dirname, 'packages'))
}

function getTkoES6Aliases () {
  return TKO_MODULES.reduce((accum, tkoModule) => Object.assign(accum, {
    [tkoModule]: path.resolve(
      LERNA_ROOT_PATH,
      `packages/${tkoModule}/dist/${tkoModule}.es6.js`
    )
  }))
}

function createRollupConfig ({ minify, transpile } = {}) {
  let filename = path.join(PACKAGE_ROOT_PATH, 'dist', LERNA_PACKAGE_NAME)

  const plugins = [...UNIVERSAL_PLUGINS]

  if (transpile) {
    plugins.push(typescript(TYPESCRIPT_CONFIG))
  } else {
    /* must come before resolve plugin */
    plugins.unshift(alias(getTkoES6Aliases()))
    filename += '.es6'
  }

  if (minify) {
    plugins.push(babelMinify({ comments: false }))
    filename += '.min'
  }

  filename += '.js'

  return {
    plugins,
    input: INPUT_FILE,
    external: IS_BROWSER_BUNDLE ? undefined : TKO_MODULES,
    output: {
      file: filename,
      format: IS_BROWSER_BUNDLE ? 'umd' : 'es',
      name: LERNA_PACKAGE_NAME === 'tko' ? 'ko' : LERNA_PACKAGE_NAME
    },
    sourcemap: true
  }
}