spec says update() should resolve to a registration, but browsers do different things

[wanderview]

See the uses of "Resolve Job Promise" in update and install algorithms:

https://w3c.github.io/ServiceWorker/#ref-for-resolve-job-promise%E2%91%A0
https://w3c.github.io/ServiceWorker/#ref-for-resolve-job-promise%E2%91%A1

They pass a registration to "Resolve Job Promise". That algorithm then says to expose it to script for either register or update jobs:

https://w3c.github.io/ServiceWorker/#resolve-job-promise-algorithm

AFAICT we don't have any WPT tests that actually assert the resolved value of update(). As a result we have an incompatibility:

• Firefox and chrome resolve undefined.
• Edge and Safari TP resolve a registration

I'm inclined to conform to the spec and edge/safari here. And I can write a WPT test.

@jakearchibald @jungkees @mattto What do you think?

[wanderview]

I have a WPT test in P2 here:

https://bugzilla.mozilla.org/show_bug.cgi?id=1455695

[wanderview]

I decided to just align FF with the spec and edge/safari. Our fix should be in FF61. It ultimately landed in this bug:

https://bugzilla.mozilla.org/show_bug.cgi?id=1456466

The resulting WPT sync PR is:

web-platform-tests/wpt#10602

I filed a chromium issue about this here:

https://bugs.chromium.org/p/chromium/issues/detail?id=836217

Closing this issue since it seems the spec is ok.

[mfalken]

Thanks for filing the chromium issue and adding the WPT!

That's weird though... wouldn't reg.update() always resolve to reg?

[wanderview]

Pretty much, yeah. It doesn't really cause any harm, though, and could make it a bit more convenient to use.

If people want to go the other way and align on undefined, I'm happy to do that too.

The WPT has not been upstreamed yet. I ran into an unrelated issue in gecko I need to fix.

[mfalken]

I don't feel strongly. At least it seems right to upstream the WPT to match the spec.

[wanderview]

FYI, the WPT test has now merged upstream.

[leonhsl]

Do we need to update the spec?
https://w3c.github.io/ServiceWorker/#serviceworkerregistration

[NewObject] Promise<void> update();
=>
[NewObject] Promise<ServiceWorkerRegistration> update();

[mfalken]

@leonhsl Good catch, yes that should be updated.