[Engine] expose an updated callback for services

[kevinv11n]

Description

Engine services currently have these callbacks:

export interface ServiceDef {
    wiring?: ServiceCallback;
    connected?: ServiceCallback;
    disconnected?: ServiceCallback;
    rendered?: ServiceCallback;
    piercing?: MembranePiercingCallback;
}

This issue proposes an additional callback: updated. This is fired once if one or more tracked properties are updated.

Wire service will leverage this. It will allow wire service to stop monkey patching the component instance with setters to intercept updates to properties used in its DSL ($-prefixed variables). It will reduce an additional microtask used to collect all property changes.

More details to come.

[kevinv11n]

fyi @caridy @yungcheng

[caridy]

@kevinv11n is this still something that we need to consider? or can this be closed?

[kevinv11n]

We’ll move @wire to a real decorator in the future which makes the service usable in other frameworks. Property descriptor hooks remain the approach which will still require a microtask to queue for when all property updates are complete.

[jbenallen]

The @wire decorator implementation will need access to the element's lifecycle callbacks, which means that its implementation will need access to privileged hooks as it has through the service hooks today. It's the same technical obstacles related to #512.