Event Reflection

[makspll]

What problem does this solve or what need does it fill?

Support/Enforce reflection for events.

Otherwise the only way to dynamically interact with these things, is to manually register every event you'd want your app to interact with through the type registry yourself, but not all of them will implement reflection.

What solution would you like?

• App::add_event should bound T: Reflect and register the involved types with the type registry (Events<T>, T, etc..).
  OR
• have #[derive(Event)]#[event(Reflect)] (or just a special ReflectEvent type data) macro functionality and implement it around bevy (less stringent, but also less likely to be useful).
  OR
• Implement a sort of sub-genre of reflection specifically for events (only require ability to construct them, find them by name etc)

[MrGVSV]

This might be slightly complicated by the fact we want to keep reflection behind a feature. But I think it could be doable to require reflection when that feature is enabled. At worst, users should be able to mark a type #[reflect(opaque)] if reflection just isn't possible or difficult to get right (e.g. due to generics).

[makspll]

Ah actually and if the requirement is behind a feature flag, it would introduce the possibility of breaking crates which have it disabled when used with crates which have it enabled :/

[makspll]

maybe TypeData is a good step in this direction