registerOfflineWorker

Registers the offline shell service worker, so a field device with no signal opens the app instead of a browser error page.

import { registerOfflineWorker } from '@conduction/nextcloud-vue'

await registerOfflineWorker({ scriptUrl: '/apps/dossiq/js/offline-sw.js' })

Argument	Type	Default	What it is
scriptUrl	string	required	where the host serves the worker from
scope	string	the script's folder	the scope to claim
container	object	navigator.serviceWorker	a container to register against, for tests

Returns the registration, or null.

It registers nothing by itself

A service worker changes how every request from an origin is answered, for every app on that origin, until somebody unregisters it. A library that installed one as a side effect of being imported would take that decision away from the app that owns the origin, and take it silently. Importing this module registers nothing: the host calls it, or gets no worker.

Where it returns null

• The browser has no service worker support.
• No scriptUrl was named.
• The registration was refused, for instance on an insecure origin. It warns and returns null rather than throwing, because the leaf captures and queues perfectly well without a worker: the worker only decides whether the shell opens with no signal, not whether anything can be recorded.

What the worker does and refuses to do

It caches the shell and the built bundle. It never answers an object read from cache, and never a write.

A cached read looks exactly like a fresh one, so somebody would be shown a status, an address or an assignment from an earlier moment with nothing on screen to say how old it is, and would act on it in front of a citizen. Stale data belongs in the planning cache, which carries an expiry and a download time and says out loud when it is out of date. A cached write would be a claim to have reached the server, which is the one thing the queue exists to make visible.

A new bundle version replaces the cache rather than adding to it. One cache per release serves last month's bundle to whichever request hits the older entry, and grows without limit on a device nobody clears.

What it cannot do

It cannot save a queue on a device nobody opens again. The queue lives in that browser profile's IndexedDB and has no server-side twin; a worker caches a page, it does not hand a queue to a server. See offlineCollection.

See also unregisterOfflineWorker.