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 sveltePreprocess from "svelte-preprocess";
import autoprefixer from "autoprefixer";
import alias from "rollup-plugin-alias";
import path from "path";

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

const preprocess = sveltePreprocess({
    transformers: {
        scss: { sourceMap: false },
        postcss: { plugins: [autoprefixer] }
    }
});

export default {
    client: {
        input: config.client.input(),
        output: config.client.output(),
        plugins: [
            replace({
                "process.browser": true,
                "process.env.NODE_ENV": JSON.stringify(mode),
                "pkg.version": JSON.stringify(pkg.version)
            }),
            svelte({
                dev,
                hydratable: true,
                emitCss: true,
                preprocess
            }),
            resolve({ browser: true }),
            commonjs(),
            alias({
                resolve: [".js", ".mjs", ".html", ".svelte"],
                "~": path.join(__dirname, "./src")
            }),

            legacy &&
                babel({
                    extensions: [".js", ".mjs", ".html", ".svelte"],
                    runtimeHelpers: true,
                    exclude: ["node_modules/@babel/**"],
                    presets: [["@babel/preset-env"]],
                    plugins: [
                        "@babel/plugin-syntax-dynamic-import",
                        [
                            "@babel/plugin-transform-runtime",
                            {
                                useESModules: true
                            }
                        ]
                    ]
                }),

            !dev &&
                terser({
                    module: true,
                    numWorkers: 1
                })
        ],
        onwarn(message, warn) {
            if (/@sapper/.test(message)) return;
            if (/svelte-transitions/.test(message)) return;
            if (/eases-jsnext/.test(message)) return;
            warn(message);
        }
    },

    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(),
            commonjs(),
            alias({
                resolve: [".js", ".mjs", ".html", ".svelte"],
                "~": path.join(__dirname, "./src")
            })
        ],
        external: Object.keys(pkg.dependencies).concat(
            require("module").builtinModules ||
                Object.keys(process.binding("natives"))
        ),
        onwarn(message, warn) {
            if (/@sapper/.test(message)) return;
            if (/svelte-transitions/.test(message)) return;
            if (/eases-jsnext/.test(message)) return;
            warn(message);
        }
    },

    serviceworker: {
        input: config.serviceworker.input(),
        output: config.serviceworker.output(),
        plugins: [
            resolve(),
            replace({
                "process.browser": true,
                "process.env.NODE_ENV": JSON.stringify(mode)
            }),
            commonjs(),
            alias({
                resolve: [".js", ".mjs", ".html", ".svelte"],
                "~": path.join(__dirname, "./src")
            }),
            !dev && terser({ numWorkers: 1 })
        ]
    }
};