ensureRegistered: ensureRegistered may not detect channel registration

[matthiasgeihs]

Location

client/adjudicate.go

Problem

func ensureRegistered currently tries determines whether a channel is registered by checking whether a registered event is seen on the event subscription. However, since our subscription only returns the latest event, it may miss the registered event. In particular, it may see a ProgressedEvent or a ConcludedEvent, but not the corresponding RegisteredEvent, and in such a case will not detect the channel as registered.

(This, by the way, shows a downside of our subscription logic. I think it is worth discussing what are actually the benefits of only returning the latest events. At the moment I rather see disadvantages, namely a more complex implementation and potential problems in usage as described above.)

Proposal

To ensure that a registered channel is detected even if the RegisteredEvent is not the latest event on the subscription, we should additionally check for ProgressedEvent and ConcludedEvent.