rollup.config.js

import svelte from 'rollup-plugin-svelte'
import commonjs from '@rollup/plugin-commonjs'
import resolve from '@rollup/plugin-node-resolve'
import livereload from 'rollup-plugin-livereload'
import { terser } from 'rollup-plugin-terser'
import sveltePreprocess from 'svelte-preprocess'
import typescript from '@rollup/plugin-typescript'
import scss from 'rollup-plugin-scss'
import { optimizeCss, optimizeImports } from 'carbon-preprocess-svelte'

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)
		},
	}
}

export default {
	input: 'src/main.ts',
	output: {
		sourcemap: true,
		format: 'iife',
		name: 'app',
		file: 'public/build/bundle.js',
	},
	plugins: [
		svelte({
			preprocess: [
				sveltePreprocess({ sourceMap: !production }),
				optimizeImports(), // https://github.com/carbon-design-system/carbon-preprocess-svelte#optimizeimports
				!production && optimizeCss(), // https://github.com/carbon-design-system/carbon-preprocess-svelte#optimizecss
				// elements(), // https://github.com/carbon-design-system/carbon-preprocess-svelte#elements
				// icons(), // https://github.com/carbon-design-system/carbon-preprocess-svelte#icons
				// pictograms(), // https://github.com/carbon-design-system/carbon-preprocess-svelte#pictograms
			],
			compilerOptions: {
				// enable run-time checks when not in production
				dev: !production,
			},
			onwarn: (warning, handler) => {
				const { code, frame } = warning
				if (code === 'css-unused-selector') return

				handler(warning)
			},
		}),
		scss({
			verbose: true,
			failOnError: true,
			includePaths: ['node_modules/**/*.scss', 'src/**/*.scss'],
			watch: ['src'],
			output: 'public/build/bundle.css',
		}), // will output compiled styles to output.css
		// we'll extract any component CSS out into
		// a separate file - better for performance
		// css({ output: '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/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('public'),

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