rollup.config.js

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 json from 'rollup-plugin-json';
import autoPreprocess from 'svelte-preprocess';

const production = !process.env.ROLLUP_WATCH;

export default {
	input: 'src/main.js',
	output: {
		sourcemap: true,
		format: 'iife',
		name: 'app',
		file: 'public/bundle.js'
	},
	plugins: [
		json({
		  exclude: [ 'node_modules/foo/**', 'node_modules/bar/**' ],
		}),
		svelte({
			// enable run-time checks when not in production
			dev: !production,
      preprocess: autoPreprocess({
        postcss: {
          plugins: [
            require('autoprefixer')(),
            require('postcss-import')({
            	path: ['src/style'],
            }),
            require('postcss-nested'),
          ]
        },
      }),
			// we'll extract any component CSS out into
			// a separate file — better for performance
			css: css => {
				css.write('public/bundle.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({ browser: true }),
		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
	}
};