index.js

const {resolve} = require('path');
const pwaManifest = require('@pwa/manifest');
const pwaManifestIcons = require('@pwa/manifest-icons');

const makeManifest = async manifest => {
  const m = await pwaManifest({
    "background_color": "#FFFFFF",
    "theme_color": "#FFFFFF",
    "start_url": "/?utm_source=web_app_manifest",
    ...manifest
  });

  if (manifest.icons && manifest.icons.src) {
    m.icons = await pwaManifestIcons({
      src: manifest.icons.src,
      cache: manifest.icons.cache || false,
      output: resolve(process.cwd(), `./static/manifest/icons`),
      publicPath: '/static/manifest/icons/',
      sizes: manifest.icons.sizes || [192, 512]

    });
  }

  await pwaManifest.write('./static/manifest/', m);
}

module.exports = (nextConfig = {}) => {
  return Object.assign({}, nextConfig, {
    webpack(config, options) {
      const {
        isServer,
        dev,
        buildId,
        defaultLoaders,
        config: {
          distDir
        }
      } = options

      if (!defaultLoaders) {
        throw new Error(
          'This plugin is not compatible with Next.js versions below 5.0.0 https://err.sh/next-plugins/upgrade'
        )
      }

      const {webpack, manifest} = nextConfig;

      if (!isServer && !dev) {
        makeManifest(manifest);
      }

      if (typeof webpack === 'function') {
        return webpack(config, options);
      }

      return config;
    }
  })
}