reactjscreate-react-appprogressive-web-appsworkbox

Create react app PWA manifest.json not being cached

I'm building a React app using create-react-app and I used the following command to make it from the beginning a PWA.

npx create-react-app my-app --template cra-template-pwa

After building my app, going to the browser developer tools, and look into the cache, I noticed all my images and files are cached but not my manifest.json. I can see my manifest.json being in the app since I can look at it in the dev tools and I can install the app on my computer. The problem comes when I go offline, the manifest.json is not found because it's not cached.

This is the error I see in my console when I serve the app offline:

GET http://localhost:5000/manifest.json net::ERR_INTERNET_DISCONNECTED 200

enter image description here

Service Worker generated by CRA;

import { clientsClaim } from 'workbox-core';
import { ExpirationPlugin } from 'workbox-expiration';
import { precacheAndRoute, createHandlerBoundToURL } from 'workbox-precaching';
import { registerRoute } from 'workbox-routing';
import { StaleWhileRevalidate } from 'workbox-strategies';

clientsClaim();

// Precache all of the assets generated by your build process.
// Their URLs are injected into the manifest variable below.
// This variable must be present somewhere in your service worker file,
// even if you decide not to use precaching. See https://cra.link/PWA
precacheAndRoute(self.__WB_MANIFEST);

// Set up App Shell-style routing, so that all navigation requests
// are fulfilled with your index.html shell. Learn more at
// https://developers.google.com/web/fundamentals/architecture/app-shell
const fileExtensionRegexp = new RegExp('/[^/?]+\\.[^/]+$');
registerRoute(
  // Return false to exempt requests from being fulfilled by index.html.
  ({ request, url }) => {
    // If this isn't a navigation, skip.
    if (request.mode !== 'navigate') {
      return false;
    } // If this is a URL that starts with /_, skip.

    if (url.pathname.startsWith('/_')) {
      return false;
    } // If this looks like a URL for a resource, because it contains // a file extension, skip.

    if (url.pathname.match(fileExtensionRegexp)) {
      return false;
    } // Return true to signal that we want to use the handler.

    return true;
  },
  createHandlerBoundToURL(process.env.PUBLIC_URL + '/index.html')
);

// An example runtime caching route for requests that aren't handled by the
// precache, in this case same-origin .png requests like those from in public/
registerRoute(
  // Add in any other file extensions or routing criteria as needed.
  ({ url }) => url.origin === self.location.origin && url.pathname.endsWith('.png'), // Customize this strategy as needed, e.g., by changing to CacheFirst.
  new StaleWhileRevalidate({
    cacheName: 'images',
    plugins: [
      // Ensure that once this runtime cache reaches a maximum size the
      // least-recently used images are removed.
      new ExpirationPlugin({ maxEntries: 50 }),
    ],
  })
);

// This allows the web app to trigger skipWaiting via
// registration.waiting.postMessage({type: 'SKIP_WAITING'})
self.addEventListener('message', (event) => {
  if (event.data && event.data.type === 'SKIP_WAITING') {
    self.skipWaiting();
  }
});```
Solution

  • The caching of manifest.json in PWAs presents a unique challenge due to its location in the public/ folder of PWA templates. As it resides outside the src folder, conventional approaches like InjectManifest may not pick it up.

    For a detailed discussion on this issue, refer to these threads:

    1. Thread on Twitter
    2. GitHub Discussion

    As noted in the GitHub thread, adding manifest.json to self.__WB_MANIFEST and precaching it doesn't offer a straightforward solution.

    One approach is to treat manifest.json as any other static resource and apply the StaleWhileRevalidate strategy. To do so, add manifest.json criteria to the latest registerRoute:

    // An example runtime caching route for requests that aren't handled by the
// precache, in this case same-origin .png requests like those from in public/
registerRoute(
  ({ url }) => {
    const isPng = url.origin === self.location.origin && url.pathname.endsWith('.png');
    const isManifestJson = url.pathname === '/manifest.json';
    return isPng || isManifestJson;
  },  
  new StaleWhileRevalidate({
    cacheName: 'images',
    plugins: [
      // Ensure that once this runtime cache reaches a maximum size,
      // the least-recently used images are removed.
      new ExpirationPlugin({ maxEntries: 50 }),
    ],
  })
);