[Property Editor] Ensure DTD APIs are available before calling them

[elliette]

See comment here: #8598 (comment)

[elliette]

@DanTup Where / when is the initialized event being sent? (I'm wondering it it's possible it's sent before DevTools connects to the DTD connection.)

[DanTup]

hmm, this might be an oversight...

The event is sent by the server after it registers all of the LSP handlers. However both of these will happen well before you connect. When you connect to DTD, we transmit all registered services so you know they're available, but because initialized is an event, there's no re-transmission of that.

I don't know if it makes sense to re-transmit events like this, because this event was quite LSP-specific. Ignoring initialized, a client generally wouldn't want to know that DTD has finished sending it the existing services, because in general there's nothing to say new services won't be registered milliseconds later.

I wonder if the simplest thing would be for the property editor to just show a spinner until it has the services it expects registered, perhaps with a timeout (of a few seconds) that says no editor is available? In theory, no users should see this because the editors shouldn't be showing a property editor iframe when those services would not be available?

[elliette]

Sounds good, opened #8788