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 css from 'rollup-plugin-css-only';
import config from 'sapper/config/rollup.js';
import replace from '@rollup/plugin-replace';
import url from '@rollup/plugin-url';
import path from "path";
import pkg from './package.json';

const mode = process.env.NODE_ENV;
const dev = mode === 'development';
const legacy = !!process.env.SAPPER_LEGACY_BUILD;
const production = !process.env.ROLLUP_WATCH;

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

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.js',
  output: {
    sourcemap: true,
    format: 'iife',
    name: 'app',
    file: 'docs/build/bundle.js'
  },
  plugins: [
    svelte({
      compilerOptions: {
        // enable run-time checks when not in production
        dev: !production
      }
    }),
    // 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(),

    // In dev mode, call `npm run start` once
    // the bundle has been generated
    !production && serve(),

    // Watch the `docs` directory and refresh the
    // browser on changes when not in production
    !production && livereload('docs'),

    // If we're building for production (npm run build
    // instead of npm run dev), minify
    production && terser()
  ],
  watch: {
    clearScreen: false
  },
  client: {
    input: config.client.input(),
    output: config.client.output(),
    plugins: [
      replace({
        preventAssignment: true,
        values: {
          'process.browser': true,
          'process.env.NODE_ENV': JSON.stringify(mode)
        },
      }),
      svelte({
        compilerOptions: {
          dev,
          hydratable: true
        }
      }),
      url({
        sourceDir: path.resolve(__dirname, 'src/node_modules/images'),
        publicPath: '/client/'
      }),
      resolve({
        browser: true,
        dedupe: ['svelte']
      }),
      commonjs(),

      legacy && babel({
        extensions: ['.js', '.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
      })
    ],

    preserveEntrySignatures: false,
    onwarn,
  },

  server: {
    input: config.server.input(),
    output: config.server.output(),
    plugins: [
      replace({
        preventAssignment: true,
        values: {
          'process.browser': false,
          'process.env.NODE_ENV': JSON.stringify(mode)
        },
      }),
      svelte({
        compilerOptions: {
          dev,
          generate: 'ssr',
          hydratable: true
        },
        emitCss: false
      }),
      url({
        sourceDir: path.resolve(__dirname, 'src/node_modules/images'),
        publicPath: '/client/',
        emitFiles: false // already emitted by client build
      }),
      resolve({
        dedupe: ['svelte']
      }),
      commonjs()
    ],
    external: Object.keys(pkg.dependencies).concat(
        require('module').builtinModules),
    preserveEntrySignatures: 'strict',
    onwarn,
  },
  serviceworker: {
    input: config.serviceworker.input(),
    output: config.serviceworker.output(),
    plugins: [
      resolve(),
      replace({
        preventAssignment: true,
        values: {
          'process.browser': true,
          'process.env.NODE_ENV': JSON.stringify(mode)
        },
      }),
      commonjs(),
      !dev && terser()
    ],
    preserveEntrySignatures: false,
    onwarn,
  }
};