rollup.config.js

import fs from "fs";
import path from "path";

import nodeResolve from "rollup-plugin-node-resolve";
import babel from "rollup-plugin-babel";
import commonjs from "rollup-plugin-commonjs";
import { list as babelHelpersList } from "@babel/helpers";
import pkg from "./package.json";

// it's important to mark all subpackages of data-fns as externals
// see https://github.com/Hacker0x01/react-datepicker/issues/1606
const dateFnsDirs = fs
  .readdirSync(path.join(".", "node_modules", "date-fns"))
  .map(d => `date-fns/${d}`);

const config = {
  output: {
    format: process.env.BABEL_ENV
  },
  plugins: [
    nodeResolve({
      mainFields: ["module"],
      extensions: [".js", ".jsx"]
    }),
    babel({
      exclude: "node_modules/**",
      plugins: [
        "@babel/plugin-external-helpers",
        "@babel/plugin-proposal-class-properties"
      ],
      runtimeHelpers: true,
      externalHelpersWhitelist: babelHelpersList.filter(
        helperName => helperName !== "asyncGenerator"
      )
    }),
    commonjs()
  ],
  external: Object.keys(pkg.dependencies)
    .concat(Object.keys(pkg.peerDependencies))
    .concat(dateFnsDirs)
};

export default config;