Don't delete marked children on parent despawn

[karmic tinsel]

is there some way to mark a child to be orphaned instead of despawned when its parent gets despawned?

[sick pine]

You can use on On<Remove> to detect when the parent is being removed and remove the child-parent relation from the child.
Or you can create your own relation that does not have linked_spawn https://taintedcoders.com/bevy/relationships.

[junior heron]

creating your own relationship would not propagate Transform changes

[primal jolt]

unless you add the transform propagation plugin with that relationship as the generic parameter

[karmic tinsel]

I already tried that, but couldn't get it to work because the ordering seems to be wrong

when I try to remove ChildOf or use the remove_child command, it seems to run after the despawn

[primal jolt]

Commands or &mut World?

[sick pine]

Hm in that case I would probably create command that takes entity Id and do the despawnig together with removechild(ot just manually remove children in such cases - do you have a lot of places in code like this to need generic approach?

[karmic tinsel]

I was using commands

[primal jolt]

using &mut World is better in observers, since it happens immediately and observers are already exclusive

[karmic tinsel]

Instead of &mut World, use either DeferredWorld if you do not need structural changes, or Commands if you do.

I got this error when I tried that

[primal jolt]

my information may be outdated ww

hm, what's it say right before and after that?

[karmic tinsel]

just that the exclusive system may not be used as an observer

[junior heron]

&mut World is UB in observers

https://github.com/bevyengine/bevy/pull/19033

[karmic tinsel]

kind of yeah unfortunately

I don’t want to make a different relationship because then I have to traverse 2 types of children when doing hierarchy stuff

[sick pine]

app.add_observer(on_despawn_with_children_orphaned_request) // global observer

#[derive(EntityEvent)]
pub struct DespawnWithChildrenOrphanedRequest(Entity);
fn on_despawn_with_children_orphaned_request(
    trigger: Trigger<DespawnWithChildrenOrphanedRequest>,
    mut commands: Commands,
) {
    let entity = trigger.entity;
    commands.entity(entity).clear_children().despawn();
}

Written by hand not tested, but the idea is that you have single, generic trigger that you can use on any entity you want. Very minimal and should work. You can try with custom command instead of trigger. It makes almost 0 overhead as for normal despawn you need commands, so instead of commands.despawn() in your system you do command.trigger().