rollup.config.js

import alias from '@rollup/plugin-alias';
import json from '@rollup/plugin-json';
import path from 'path';
import commonjs from 'rollup-plugin-commonjs';
import livereload from 'rollup-plugin-livereload';
import resolve from 'rollup-plugin-node-resolve';
import svelte from 'rollup-plugin-svelte';
import css from 'rollup-plugin-css-only'
import { terser } from 'rollup-plugin-terser';


const production = !process.env.ROLLUP_WATCH;

const customResolver = resolve({
  extensions: ['.mjs', '.js', '.svelte', '.scss'],
})

export default {
	input: 'src/main.js',
	output: {
		sourcemap: true,
		format: 'iife',
		name: 'app',
		file: 'public/bundle.js'
	},
	plugins: [
    alias({
      entries: [
        {
          find: '@src',
          replacement: path.resolve(__dirname, 'src'),
        },
      ],
      customResolver,
    }),
    json(),
		svelte({
			// enable run-time checks when not in production
			dev: !production,
			// we'll extract any component CSS out into
			// a separate file — better for performance
			css: css => {
				css.write('bundle.css');
			}
    }),
    css({
      output: 'highlight.css'
    }),

		// If you have external dependencies installed from
		// npm, you'll most likely need these plugins. In
		// some cases you'll need additional configuration —
		// consult the documentation for details:
		// https://github.com/rollup/rollup-plugin-commonjs
		resolve(),
		commonjs(),

		// Watch the `public` directory and refresh the
		// browser on changes when not in production
		!production && livereload('public'),

		// If we're building for production (npm run build
		// instead of npm run dev), minify
		production && terser()
	],
	watch: {
		clearScreen: false
	}
};