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";
import postcss from "rollup-plugin-postcss";
import PurgeSvelte from "purgecss-from-svelte";
import path from "path";

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 postcssPlugins = (purgecss = false) => {
  return [
    require("postcss-import")(),
    require("postcss-url")(),
    require("tailwindcss")("./tailwind.config.js"),
    require("autoprefixer")(),
    // Do not purge the CSS in dev mode to be able to play with classes in the browser dev-tools.
    purgecss &&
      require("@fullhuman/postcss-purgecss")({
        content: ["./**/*.svelte", "./src/template.html"],
        extractors: [
          {
            extractor: PurgeSvelte,

            // Specify the file extensions to include when scanning for
            // class names.
            extensions: ["svelte", "html"]
          }
        ],
        // Whitelist selectors to stop Purgecss from removing them from your CSS.
        whitelist: []
      }),
    !dev && require("cssnano")
  ].filter(Boolean);
};

const preprocess = getPreprocessor({
  transformers: {
    postcss: {
      plugins: postcssPlugins() // Don't need purgecss because Svelte handle unused css for you.
    }
  }
});

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,
				emitCss: 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(),
			postcss({
        plugins: postcssPlugins(!dev),
        extract: path.resolve(__dirname, "./static/global.css")
      })
		],
		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,
	}
};