rollup.config.js

import fs from 'fs';
import svelte from 'rollup-plugin-svelte';
import resolve from '@rollup/plugin-node-resolve';
import commonjs from '@rollup/plugin-commonjs';
import livereload from 'rollup-plugin-livereload';
import { terser } from 'rollup-plugin-terser';
import sveltePreprocess from 'svelte-preprocess';
import typescript from '@rollup/plugin-typescript';
import posthtml from 'posthtml';
import { hash } from 'posthtml-hash';
import rimraf from 'rimraf';
import copy from 'rollup-plugin-copy';

const production = !process.env.ROLLUP_WATCH;

function serve() {
	let server;
	
	function toExit() {
		if (server) server.kill(0);
	}

	return {
		writeBundle() {
			if (server) return;
			server = require('child_process').spawn('npm', ['run', 'start', '--', '--dev'], {
				stdio: ['ignore', 'inherit', 'inherit'],
				shell: true
			});

			process.on('SIGTERM', toExit);
			process.on('exit', toExit);
		}
	};
}

function hashAssets() {
	return {
		name: 'hash-assets',
		buildStart() {
			rimraf.sync('build');
		},
		writeBundle() {
			posthtml([
				hash({ path: 'build/' }),
			])
			.process(fs.readFileSync('./build/index.html'))
			.then((result) => fs.writeFileSync('./build/index.html', result.html));
		}
	}
}

export default {
	input: 'src/main.ts',
	output: {
		sourcemap: !production,
		format: 'iife',
		name: 'app',
		file: 'build/bundle.[hash].js'
	},
	plugins: [
		copy({
			targets: [{
				src: 'public/*',
				dest: 'build',
			}],
		}),
		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.[hash].css', !production);
			},
			preprocess: sveltePreprocess(),
		}),

		// 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/plugins/tree/master/packages/commonjs
		resolve({
			browser: true,
			dedupe: ['svelte']
		}),
		commonjs(),
		typescript({
			sourceMap: !production,
			inlineSources: !production
		}),

		// In dev mode, call `npm run start` once
		// the bundle has been generated
		!production && serve(),

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

		// If we're building for production (npm run build
		// instead of npm run dev), minify
		production && terser(),

		production && hashAssets()
	],
	watch: {
		clearScreen: false
	}
};