On the latest version of Firefox beta (Ubuntu snap, 95.0b6), I get a prompt to use the "system handler" when opening a localhost link (e.g. http://localhost:3000)

I tried a couple of nightlies (2021-11-01, 2021-11-10) via mozregression and neither of them exhibited this problem, which makes me wonder if this problem is snap specific.

Still happening in 95.0b12

Oh wait, I see what's going on. If I type http://localhost:3000 into the URL bar everything works as expected. Somehow it's interpreting localhost as a protocol handler.

This is probably similar to bug 1618094, but I am not sure if the flatpak issue applies to snap as well.

The Bugbug bot thinks this bug should belong to the 'Core::Widget: Gtk' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

I can see the prompt when I type e.g. localhost:3000 in the address bar and press enter.
However clicking on the hyperlink in the description of this bug does the right thing, probably because the target of the link is http://localhost:3000 (scheme included).

This is with the snap version 97.0 (currently in the candidate channel, expected to be promoted to stable later today).

I can confirm the deb package for the same version isn't affected.

Related: bug 1744243.

This appears to be working now, though I'm now seeing bug 1756083 which might be related.

William, do you still experience this? I can't repro on an uptodate 102 snap. From Olivier's comment, 97.0 was already supposed to be fixed, so I suspect we should mark this as RESOLVED:FIXED?

I think it's a clear dupe of Bug 1618094, we landed a workaround for it, but it introduced a related problem of not being trivial to add a new handler (that is tracked in bug 1786132)