Library Affected:
workbox-window

Browser & Platform:
At least Chrome 131.0.6778.86, possibly all browsers

Issue or Feature Request Description:

The WorkboxLifecycleEvent.isUpdate will remain false in following scenario:

1. New service worker installation
2. Alter source code to trigger update in next step
3. Manually trigger Service worker update (without navigation/ page reload), for ie. by one of;
   • DevTools > Application > Service workers > Update
   • (await navigator.serviceWorker.getRegistration()).update()

This matches the behavior described in source:

However it's name leads to false assumption that it's value is true on any update (even that there was no controlling service worker at the time of registration).

Some examples:

• chrome for developers > Workbox-window docs > When an updated version of the service worker is found:

  When a new service worker starts installing but an existing version is currently controlling the page, the isUpdate property of all the following events will be true.

• web.dev > Broadcast updates to pages with service workers > Listen to service worker lifecycle events

  wb.addEventListener('installed', (event) => {
    if (event.isUpdate) {
      // Show "Update App" banner
    }
  });

• demos > workbox-window

  workbox/demos/src/workbox-window/index.html

  Lines 53 to 57 in c77dceb

  	wb.addEventListener('activated', (event) => {
  	// `event.isUpdate` will be true if another version of the service
  	// worker was controlling the page when this version was registered.
  	if (!event.isUpdate) {
  	console.log('Service worker activated for the first time!');

Suggested solution

I think the fix is to set this._isUpdate = true after first installation:

diff --git a/packages/workbox-window/src/Workbox.ts
    private readonly _onControllerChange = (originalEvent: Event) => {
      const sw = this._sw;
      const isExternal = sw !== navigator.serviceWorker.controller;

+     this._isUpdate = true
+     this._isUpdate = navigator.serviceWorker.controller !== null // Alternative implementation

and adjust jsdoc comments for this property.

I'm just not entirely sure if this is the right place?

Related PR: #1905