rollup.config.js

import merge from 'deepmerge';
// use createSpaConfig for bundling a Single Page App
import { createSpaConfig } from '@open-wc/building-rollup';
import copy from 'rollup-plugin-copy';

// use createBasicConfig to do regular JS to JS bundling
// import { createBasicConfig } from '@open-wc/building-rollup';

const baseConfig = createSpaConfig({
  // use the outputDir option to modify where files are output
  // outputDir: 'dist',

  // if you need to support older browsers, such as IE11, set the legacyBuild
  // option to generate an additional build just for this browser
  legacyBuild: true,

  // development mode creates a non-minified build for debugging or development
  developmentMode: process.env.ROLLUP_WATCH === 'true',

  // set to true to inject the service worker registration into your index.html
  injectServiceWorker: false,
});

// noinspection JSUnusedGlobalSymbols
export default merge(baseConfig, {
  // if you use createSpaConfig, you can use your index.html as entrypoint,
  // any <script type="module"> inside will be bundled by rollup
  input: './index.html',

  // alternatively, you can use your JS as entrypoint for rollup and
  // optionally set a HTML template manually
  // input: './app.js',

  plugins: [
    // @see https://open-wc.org/building/building-rollup.html#copying-assets
    copy({
      targets: [
        { src: 'assets', dest: 'dist' },
        { src: ['CNAME'], dest: 'dist' },
      ],
      // set flatten to false to preserve folder structure
      flatten: false,
    }),
  ],
});