Now there is no error message at all. Instead of removing the dialog, shouldn't there be a message added to inform the user, that they have to enter a password to do the action and also that no changes were made? Something like Kate does when you try to save changes to a file that requires you to enter a password and you don't enter it.

In D29333#661119, @mthw wrote:

Now there is no error message at all. Instead of removing the dialog, shouldn't there be a message added to inform the user, that they have to enter a password to do the action and also that no changes were made? Something like Kate does when you try to save changes to a file that requires you to enter a password and you don't enter it.

This change only suppresses the dialog when the error message returned from the job is empty. If you cancel the password dialog, I'm not sure any extra notification is needed. Canceling an operation is pretty self-explanatory in the user's mind.

I would like KAuth or Polkit to be fixed to properly report user canceling

Yeah, this is also an issue when clicking cancel on a password prompt in sddm-kcm's GHNS and when clicking Reset in the Advanced tab. And when canceling theme deletion an empty inline message pops up :/

We could work around all four though. I'm of the opinion that it's better to have a workaround if waiting for a proper fix will take time. I also agree with @ngraham that no notification is needed when an auth dialog is canceled.

Discover has the same issue. I guess I should look into fixing KAuth or Polkit or whatever is responsible for this.