React App hosted in Firebase Hosting - Uncaught SyntaxError: Unexpected token '<' - reactjs

Question

I've seen at least 4 threads with the same problem and tried solutions from them, but none of them worked for me.
When I deploy my react app to firebase hosting I get blank page and a following error:
The only way to get it working is to empty cache and hard reload, but then reloading it again would cause exactly the same error.
I double checked my build html gets assets from correct folders using %PUBLIC_URL% as part of the routes in public/index.html
I also commented out manifest and the whole registering of the serviceWorker function, then rebuild it and deployed it, but I still have exactly the same problem.
At this point I'm a bit dumbfounded cause I think it was caused by whole caching system and now that I disabled it, it still remains so I don't know anymore how this whole thing actually works
My firebase.json
{
"hosting": {
"public": "build",
"site": "react-pukinn",
"ignore": [
"firebase.json",
"**/.*",
"**/node_modules/**"
],
"rewrites": [
{
"source": "**",
"destination": "/index.html"
}
],
"headers": [
{ "source":"/serviceWorker.js", "headers": [{"key": "Cache-Control", "value": "no-cache"}] }
]
}
}
My serviceWorker.js:
let CACHE_NAME = 'pukinn';
const urlsToCache = [
'/',
'/index.html',
];
self.addEventListener('install', (event) => {
// Perform install steps
event.waitUntil(
caches.open(CACHE_NAME)
.then(function(cache) {
console.log('Opened cache');
return cache.addAll(urlsToCache);
})
);
});
self.addEventListener('fetch', (event) => {
event.respondWith(caches.match(event.request)
.then(function(response) {
if (response) {
return response;
}
return fetch(event.request);
})
);
});
self.addEventListener('install', (event) => {
// Perform install steps
event.waitUntil(
caches.open(CACHE_NAME)
.then(function(cache) {
console.log('Opened cache');
return cache.addAll(urlsToCache);
})
);
self.skipWaiting();
});
manifest.json
{
"short_name": "Púkinn",
"name": "Púkinn",
"icons": [
{
"src": "favicon.ico",
"sizes": "64x64 32x32 24x24 16x16",
"type": "image/x-icon"
},
{
"src": "icons/knight_demon-192x192-min.png",
"type": "image/png",
"sizes": "192x192"
},
{
"src": "icons/knight_demon-512x512-min.png",
"type": "image/png",
"sizes": "512x512"
}
],
"start_url": "index.html",
"display": "standalone",
"theme_color": "#ed1c24",
"background_color": "#212121"
}

Answer 1

I found the problem. My serviceWorker.js file was in the root of the project instead of my ./src folder. So what happed is that on build it did not include it into build folder that is used for hosting.
Really dumb mistake on my part.