Is beforeunload fired in all cases?

[domenic]

Based on some initial tests in web-platform-tests/wpt#36488, in Chrome and Safari navigating or traversing to a javascript: URL does not fire beforeunload. Whereas in Firefox it does fire.

In the current spec all navigations and traversals fire beforeunload, whereas in the current state of the rewrite (#6315) only those which require a fetch will do so. So the following are the tricky cases:

• javascript: URLs
• srcdoc resources
• embed/object
• non-fetch scheme documents

[smaug----]

It would be rather surprising if beforeunload behavior was bound to fetch. beforeunload, as the name hints, is about unloading the current page before something replaces it.

[domenic]

I can see that reasoning, but, (a) requiring waiting on cross-process messages for what would otherwise be very simple navigations is not great; and (b) beforeunload is generally bad, so the less of it we fire, the better IMO. If it's already not fired in 2/3 browsers in these cases, I'm inclined to spec that behavior.

This is pending some test results for the non-javascript: cases, though.