Multiple controlling events

[joshkel]

Library Affected: workbox-window

Browser & Platform: Tested on Chrome 89.0.4389.114 for Mac

Issue or Feature Request Description:

I'm having trouble getting the Workbox class's controlling event to work like I expect - or maybe I'm misunderstanding how it's expected to work.

Scenario: I want my page to reload on update, like in the recipe:

wb.addEventListener('controlling', (event) => {
  window.location.reload();
});

However, unlike the recipe, I want my page to reload even if the update was confirmed in the UI in another browser tab. So I set up this event handler at application start, instead of in response to a waiting event. (That was working even prior to #2786 and Workbox 6.1.5, so I may be misunderstanding #2786.)

Then I noticed that my page would reload when it was first loaded (because the newly installed service worker takes control via clientsClaim). That seems unnecessary, so I added a check for that:

wb.addEventListener('controlling', (event) => {
  if (!event.isUpdate) {
    window.location.reload();
  }
});

However, I then discovered that the controlling event can only fire once: a newly loaded page gets the controlling event for the initial load, so it then no longer gets events notifying of future updates.

This seems like a bug, but I could easily be misunderstanding something. Is this the desired behavior?

[jeffposnick]

Thanks for catching that, @joshkel. My supposition is that

workbox/packages/workbox-window/src/Workbox.ts

Lines 191 to 192 in ef225a9

	navigator.serviceWorker.addEventListener(
	'controllerchange', this._onControllerChange, {once: true});

was written with {once:true} originally, as an optimizing for when there was no concept of "external" controlling events in workbox-window, and that we should have removed the {once: true} when we added support for all types of controlling events, regardless of whether they originated from the page's original service worker, or a new service worker on a different page.

I think you're already familiar with our codebase, so if you want to take on removing that {once: true}, you are encouraged to! Otherwise, we can.

[jeffposnick]

The fix is now deployed in a pre-release of Workbox v6.2.0: https://github.com/GoogleChrome/workbox/releases/tag/v6.2.0-alpha.0