Non-simple CORS preflight fails due to cache-control header

• Component: Service Workers
• Status: RESOLVED FIXED

[Kevin Twesten]

When sending a non-simple CORS request (e.g. some JSON via sendBeacon), a "cache-control" header is added to the preflight request when it is fetched by a Service Worker.
Since this is unexpected for most of the servers, the sendBeacon request fails in that case.

I implemented a simple test page that reproduces the issue here: https://falling-bolt-17.app.baqend.com/
The test page registers a simple Service Worker which listens to fetch requests and tries to fetch them.
It also includes the following script tag that sends the beacon request:
	<script>
		// dummy data
		var data = '{"currency":"EUR","is_logged_in":false,"producer_properties":{"common":{"sent_by":"","timestamp":"2022-02-15T07:02:51.078Z","producer_id":"","tracking_method":"collector","application_version":""},"web_frontend":{"platform":"desktop","user_agent":"","view_id":"","container_name":"","visitor_id":"","domain":"","url":"","referrer_url":""}}}';
		// create blob with data for beachon
		var blob = new Blob([data], { type: 'application/vnd.gyg.v2+json' });
		// send beacon request
		navigator.sendBeacon('https://collector.getyourguide.com/track/HomePageRequest', blob);
	</script>

Ways to reproduce:
1. Go to https://falling-bolt-17.app.baqend.com/
2. Open JavaScript console
3. Refresh the page
4. Check the request headers of the 'HomePageRequest' request on the network tab and notice that it failed and that a "cache-control" header with the value "max-age=0" was added 

The error can also be seen in the Service Worker console (Develop -> Service Workers).


Is there any fix for this issue?

[Radar WebKit Bug Importer]

<rdar://problem/89382796>

[youenn fablet]

Created attachment 453082 [details]
Patch

[youenn fablet]

Created attachment 453096 [details]
Patch

[EWS]

Committed r290507 (247792@main): <https://commits.webkit.org/247792@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 453096 [details].

[youenn fablet]

*** Bug 236973 has been marked as a duplicate of this bug. ***