jekyll + service worker failure : service worker does not successfully serve the manifest's start_url

Question

I can't set up the service worker for the Jekyll-powered project site - Lighthouse is refusing start_url value and giving an error Unable to fetch start URL via service worker

app->manifest output shows root /

tried ./index.html as well - same results. is there a way to pass the audit?

manifest.json:

{
  "name": "outcast",
  "short_name": "outcast",
  "icons": [
    {
      "src": "/assets/images/splsh192.png",
      "type": "image/png",
      "sizes": "192x192"
    },
    {
      "src": "/assets/images/splsh512.png",
      "type": "image/png",
      "sizes": "512x512"
    }
  ],
  "lang": "en-US",
  "display": "standalone",
  "background_color": "#131313",
  "theme_color": "#f62e1a",
  "start_url": "/",
  "serviceworker": {
   "src": "sw.js",
   "scope": "/",
   "update_via_cache": "none"
 }
}

sw.js

Answer 1

replacing fetch handler in sw.js with the code from official guide fixed the issue. still debugging undefined cache

self.addEventListener('fetch', function(event) {
  event.respondWith(
    caches.match(event.request)
      .then(function(response) {
        // Cache hit - return response
        if (response) {
          return response;
        }
        return fetch(event.request);
      }
    )
  );
});