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";

import getPreprocessor 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);

const preprocess = getPreprocessor({
	postcss: true,
	transformers: {
		postcss: {
			config: {
				path: "./postcss.config.js",
			},
		},
	},
});

export default {
	client: {
		input: config.client.input(),
		output: config.client.output(),
		plugins: [
			replace({
				"process.browser": true,
				"process.env.NODE_ENV": JSON.stringify(mode),
			}),
			svelte({
				dev,
				hydratable: true,
				preprocess,
			}),
			resolve({
				browser: true,
				dedupe: ["svelte"],
			}),
			commonjs(),

			legacy &&
				babel({
					extensions: [".js", ".mjs", ".html", ".svelte"],
					runtimeHelpers: true,
					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,
				}),
		],

		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,
				preprocess,
			}),
			resolve({
				dedupe: ["svelte"],
			}),
			commonjs(),
		],
		external: Object.keys(pkg.dependencies).concat(
			require("module").builtinModules ||
				Object.keys(process.binding("natives"))
		),

		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(),
		],

		onwarn,
	},
};