Make 'BasicHost.emitters.evtLocalAddrsUpdated' stateful.

[lthibault]

Problem

Currently, subscribing to event.EvtLocalAddrsUpdated is not stateful, meaning that subscribers will miss the initial set of addresses emitted during host initialization.

While not a huge deal (we can just call h.Addrs()), this requires additional initialization outside of the subscription logic. This is kind of annoying; I would much prefer to write:

for addrsChanged := range sub.Out() {
    do_something(addrsChanged)
}

Currently, I have to write something akin to setup(h.Addrs()) somewhere else.

Solution

The solution is to pass eventbus.Stateful to the emitter's constructor, here.

Is this doable, or will it break something? I'm happy to submit a PR if this is pre-approved in principle.

[Stebalien]

No, that seems quite reasonable. At the moment, the best approach is to: 1. Subscribe. 2. Get the current addresses. But I agree making this stateful would simplify things. Want to make a patch?

[lthibault]

Perfect! I'll have a patch ready shortly.

[lthibault]

@Stebalien See #1147.

Do you think it's worth making EvtEvtLocalProtocolsUpdated stateful as well?

[Stebalien]

Not really. The addresses one makes sense (somewhat) because it has includes all addresses. The protocols one is just for protocol updates.

I say somewhat for the addresses one because ideally it wouldn't return "removed" addresses in the first event.