rollup.config.js

import resolve from "@rollup/plugin-node-resolve";
import replace from "@rollup/plugin-replace";
import commonjs from "@rollup/plugin-commonjs";
import svelte from "rollup-plugin-svelte";
import babel from "@rollup/plugin-babel";
import { terser } from "rollup-plugin-terser";
import config from "sapper/config/rollup.js";
import pkg from "./package.json";
const sass = require("svelte-preprocess-sass").sass;
import scss from "rollup-plugin-scss";
import typescript from '@rollup/plugin-typescript';

import autoPreprocess  from 'svelte-preprocess';


const mode = process.env.NODE_ENV;
const dev = mode === "development";
const legacy = !!process.env.SAPPER_LEGACY_BUILD;

const onwarn = (warning, onwarn) => (warning.code === "CIRCULAR_DEPENDENCY" && /[/\\]@sapper[/\\]/.test(warning.message)) || onwarn(warning);

export default {
	client: {
		input: config.client.input(),
		output: config.client.output(),
		plugins: [
			scss({
				output: "static/global.css",
			}),
			replace({
				"process.browser": true,
				"process.env.NODE_ENV": JSON.stringify(mode),
			}),
			svelte({
				dev,
				hydratable: true,
				emitCss: true,
				preprocess:  autoPreprocess(),
			}),
			resolve({
				browser: true,
				dedupe: ["svelte"],
			}),
			commonjs(),
			typescript({ sourceMap: dev }),

			legacy &&
				babel({
					extensions: [".js", ".ts", ".mjs", ".html", ".svelte"],
					babelHelpers: "runtime",
					//exclude: ['node_modules/@babel/**'],
					presets: [
						[
							"@babel/preset-env",
							{
								targets: "> 0.25%, not dead",
							},
						],
					],
					plugins: [
						"@babel/plugin-syntax-dynamic-import",
						[
							"@babel/plugin-transform-runtime",
							{
								useESModules: true,
							},
						],
					],
				}),

			!dev &&
				terser({
					module: true,
					compress: { drop_console: true },
					mangle: {
						toplevel: true,
					},
					output: {
						comments: false,
					},
				}),
		],

		preserveEntrySignatures: false,
		onwarn,
	},

	server: {
		input: config.server.input(),
		output: config.server.output(),
		plugins: [
			replace({
				"process.browser": false,
				"process.env.NODE_ENV": JSON.stringify(mode),
			}),
			svelte({
				generate: "ssr",
				dev: true,
			}),
			resolve({
				dedupe: ["svelte"],
			}),
			commonjs(),
		],
		external: Object.keys(pkg.dependencies).concat(require("module").builtinModules || Object.keys(process.binding("natives"))),

		preserveEntrySignatures: "strict",
		onwarn,
	},

	serviceworker: {
		input: config.serviceworker.input(),
		output: config.serviceworker.output(),
		plugins: [
			resolve(),
			replace({
				"process.browser": true,
				"process.env.NODE_ENV": JSON.stringify(mode),
			}),
			commonjs(),
			!dev && terser(),
		],

		preserveEntrySignatures: false,
		onwarn,
	},
};