rollup.config.js

import babel from "@rollup/plugin-babel";
import commonjs from "@rollup/plugin-commonjs";
import external from "rollup-plugin-peer-deps-external";
import resolve from "@rollup/plugin-node-resolve";
import url from "@rollup/plugin-url";
import json from "@rollup/plugin-json";
import postcss from "rollup-plugin-postcss";

const { readdirSync, statSync } = require("fs");
const { join } = require("path");

const dirs = p =>
  readdirSync(p).filter(f => statSync(join(p, f)).isDirectory());

const modules = dirs("src");

const config = moduleDir => ({
  input: `src/${moduleDir}/index.js`,
  output: [
    {
      file: `src/${moduleDir}/build/index.js`,
      format: "cjs",
      sourcemap: true,
    },
    {
      file: `src/${moduleDir}/build/index.es.js`,
      format: "es",
      sourcemap: true,
    },
  ],
  external: ["react", "react-dom"],
  plugins: [
    external(),
    url(),
    json(),
    babel({
      exclude: "node_modules/**",
      presets: ["@babel/preset-react"],
      plugins: ["@babel/plugin-proposal-nullish-coalescing-operator"],
      babelHelpers: "bundled",
    }),
    resolve({
      browser: true,
    }),
    commonjs(),
    postcss({ plugins: [] }),
  ],
});

export default commandLineArgs => {
  if (commandLineArgs.hasOwnProperty("package"))
    return [config(commandLineArgs.package)];
  return modules.map(m => config(m));
};