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Observers and hooks doesn't pair well with mapped entities #14465

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#15422
Closed
Observers and hooks doesn't pair well with mapped entities#14465
#15422
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A-ECSEntities, components, systems, and eventsA-NetworkingSending data between clients, servers and machinesA-ScenesComposing and serializing ECS objectsC-BugAn unexpected or incorrect behaviorS-Needs-DesignThis issue requires design work to think about how it would best be accomplished
@Shatur

Description

@Shatur
Shatur
opened on Jul 24, 2024

Bevy version

v0.14.0

What you did

I have a component that stores an entity. The component implements and reflects MapEntities, so on scene deserialization it automatically maps entities inside it.

What went wrong

When I implement on_add hook or OnAdd observer for such component, it triggers before MapEntities which results in invalid entity access.
It happens because we insert components here:

bevy/crates/bevy_scene/src/scene.rs

Lines 117 to 123 in eabb58a

reflect_component.copy(
&self.world,
world,
scene_entity.id(),
*entity,
&type_registry,
);

But entities mapped later:

bevy/crates/bevy_scene/src/scene.rs

Lines 128 to 131 in eabb58a

for registration in type_registry.iter() {
if let Some(map_entities_reflect) = registration.data::<ReflectMapEntities>() {
map_entities_reflect.map_all_entities(world, entity_map);
}

I think we should map entities before the insertion.

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    A-ECSEntities, components, systems, and eventsA-NetworkingSending data between clients, servers and machinesA-ScenesComposing and serializing ECS objectsC-BugAn unexpected or incorrect behaviorS-Needs-DesignThis issue requires design work to think about how it would best be accomplished

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