rollup.config.js

import vuePlugin from 'rollup-plugin-vue'
import replace from '@rollup/plugin-replace'
import resolve from '@rollup/plugin-node-resolve'
import commonjs from '@rollup/plugin-commonjs'
import pascalcase from 'pascalcase'

const pkg = require('./package.json')
const name = pkg.name

function getAuthors (pkg) {
  const { contributors, author } = pkg

  const authors = new Set()
  if (contributors && contributors) {
    contributors.forEach((contributor) => {
      authors.add(contributor.name)
    })
  }
  if (author) authors.add(author.name)

  return Array.from(authors).join(', ')
}

const banner = `/*!
  * ${pkg.name} v${pkg.version}
  * (c) ${new Date().getFullYear()} ${getAuthors(pkg)}
  * @license MIT
  */`

const outputConfigs = {
  // each file name has the format: `dist/${name}.${format}.js`
  // format being a key of this object
  'esm-bundler': {
    file: pkg.module,
    format: 'es'
  },
  cjs: {
    file: pkg.main,
    format: 'cjs'
  },
  global: {
    file: pkg.unpkg,
    format: 'iife'
  },
  esm: {
    file: pkg.module.replace('bundler', 'browser'),
    format: 'es'
  }
}

const allFormats = Object.keys(outputConfigs)
const packageFormats = allFormats
const packageConfigs = packageFormats.map((format) =>
  createConfig(format, outputConfigs[format])
)

// only add the production ready if we are bundling the options
packageFormats.forEach((format) => {
  if (format === 'cjs') {
    packageConfigs.push(createProductionConfig(format))
  } else if (format === 'global') {
    packageConfigs.push(createMinifiedConfig(format))
  }
})

export default packageConfigs

function createConfig (format, output, plugins = []) {
  if (!output) {
    console.log(`invalid format: "${format}"`)
    process.exit(1)
  }

  output.sourcemap = !!process.env.SOURCE_MAP
  output.banner = banner
  output.externalLiveBindings = false
  output.globals = { vue: 'Vue', '@vue/composition-api': 'vueCompositionApi' }

  const isProductionBuild = /\.prod\.js$/.test(output.file)
  const isGlobalBuild = format === 'global'
  const isRawESMBuild = format === 'esm'
  const isNodeBuild = format === 'cjs'
  const isBundlerESMBuild = /esm-bundler/.test(format)

  if (isGlobalBuild) output.name = pascalcase(pkg.name)

  const external = ['vue', '@vue/composition-api']
  if (!isGlobalBuild) {
    external.push('@vue/devtools-api')
  }

  const nodePlugins = [resolve(), commonjs()]

  return {
    input: 'src/index.ts',
    // Global and Browser ESM builds inlines everything so that they can be
    // used alone.
    external,
    plugins: [
      vuePlugin(),
      createReplacePlugin(
        isProductionBuild,
        isBundlerESMBuild
      ),
      ...nodePlugins,
      ...plugins
    ],
    output
  }
}

function createReplacePlugin (
  isProduction,
  isBundlerESMBuild
) {
  const replacements = {
    'process.env.NODE_ENV': isBundlerESMBuild
      ? // preserve to be handled by bundlers
      'process.env.NODE_ENV'
      : // hard coded dev/prod builds
      JSON.stringify(isProduction ? 'production' : 'development'),
    __VUE_PROD_DEVTOOLS__: isBundlerESMBuild
      ? '__VUE_PROD_DEVTOOLS__'
      : 'false'
  }
  // allow inline overrides like
  // __RUNTIME_COMPILE__=true yarn build
  Object.keys(replacements).forEach((key) => {
    if (key in process.env) {
      replacements[key] = process.env[key]
    }
  })
  return replace({
    preventAssignment: true,
    values: replacements
  })
}

function createProductionConfig (format) {
  return createConfig(format, {
    file: `dist/${name}.${format}.prod.js`,
    format: outputConfigs[format].format
  })
}

function createMinifiedConfig (format) {
  const { terser } = require('rollup-plugin-terser')
  return createConfig(
    format,
    {
      file: `dist/${name}.${format}.prod.js`,
      format: outputConfigs[format].format
    },
    [
      terser({
        module: /^esm/.test(format),
        compress: {
          ecma: 2015,
          pure_getters: true
        }
      })
    ]
  )
}