Maybe Observers should have it's own event type.

[alexniver]

For my own experience, Event used by Observers and EventWriter/EventReader makes me confuse. What is Event?

I test event_writer.send(Event), It doesn't trigger observer.

use bevy::input::common_conditions::input_just_pressed;
use bevy::prelude::*;

fn main() {
    App::new()
        .add_event::<AEvent>()
        .add_plugins(DefaultPlugins)
        .add_systems(
            Update,
            write_a_event.run_if(input_just_pressed(KeyCode::Space)),
        )
        .add_observer(on_a_event)
        .run();
}

#[derive(Event)]
struct AEvent;

fn write_a_event(mut event_writer: EventWriter<AEvent>) {
    event_writer.send(AEvent);
    println!("write a event");
}

fn on_a_event(_trigger: Trigger<AEvent>) {
    println!("on a event");
}

and trigger a event, doesn't readable by event_reader

use bevy::input::common_conditions::input_just_pressed;
use bevy::prelude::*;

fn main() {
    App::new()
        .add_event::<AEvent>()
        .add_plugins(DefaultPlugins)
        .add_systems(
            Update,
            trigger_a_event.run_if(input_just_pressed(KeyCode::Space)),
        )
        .add_systems(Update, read_a_event)
        .run();
}

#[derive(Event)]
struct AEvent;

fn trigger_a_event(mut commands: Commands) {
    commands.trigger(AEvent);
    println!("trigger a event");
}

fn read_a_event(event_reader: EventReader<AEvent>) {
    if event_reader.is_empty() {
        return;
    }

    println!("read a event");
}

EventReader/EventWriter and Observer have two different behave, I think they should use two different EventType.