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Handle TriggerTargets that are combinations for components/entities #14563

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Handle TriggerTargets that are combinations for components/entities #14563

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d1c3b03
handle TriggerTargets that are combinations for components/entities
cBournhonesque Jul 31, 2024
599476c
Merge branch 'main' into cb/fix-observe-panic
alice-i-cecile Oct 8, 2024
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52 changes: 52 additions & 0 deletions crates/bevy_ecs/src/observer/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -702,6 +702,58 @@ mod tests {
assert_eq!(2, world.resource::<R>().0);
}

#[test]
fn observer_multiple_targets() {
let mut world = World::new();
let component_a = world.init_component::<A>();
let component_b = world.init_component::<B>();
world.init_resource::<R>();

// targets (entity_1, A)
let entity_1 = world
.spawn_empty()
.observe(|_: Trigger<EventA, A>, mut res: ResMut<R>| res.0 += 1)
.id();
// targets (entity_2, B)
let entity_2 = world
.spawn_empty()
.observe(|_: Trigger<EventA, B>, mut res: ResMut<R>| res.0 += 10)
.id();
// targets any entity or component
world.observe(|_: Trigger<EventA>, mut res: ResMut<R>| res.0 += 100);
// targets any entity, and components A or B
world.observe(|_: Trigger<EventA, (A, B)>, mut res: ResMut<R>| res.0 += 1000);

// TODO: ideally this flush is not necessary, but right now observe() returns WorldEntityMut
// and therefore does not automatically flush.
world.flush();

// trigger for an entity and a component
world.trigger_targets(EventA, (entity_1, component_a));
world.flush();
assert_eq!(1101, world.resource::<R>().0);
world.resource_mut::<R>().0 = 0;

// trigger for both entities, but no components: trigger once per entity target
world.trigger_targets(EventA, (entity_1, entity_2));
world.flush();
assert_eq!(200, world.resource::<R>().0);
world.resource_mut::<R>().0 = 0;

// trigger for both components, but no entities: trigger once
world.trigger_targets(EventA, (component_a, component_b));
world.flush();
assert_eq!(1100, world.resource::<R>().0);
world.resource_mut::<R>().0 = 0;

// trigger for both entities and both components: trigger once per entity target
// we only get 2211 and not 4211 because a given observer can trigger only once per entity target
world.trigger_targets(EventA, ((component_a, component_b), (entity_1, entity_2)));
world.flush();
assert_eq!(2211, world.resource::<R>().0);
world.resource_mut::<R>().0 = 0;
}

#[test]
fn observer_dynamic_component() {
let mut world = World::new();
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77 changes: 39 additions & 38 deletions crates/bevy_ecs/src/observer/trigger_event.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,8 @@ fn trigger_event<E: Event, Targets: TriggerTargets>(
targets: Targets,
) {
let mut world = DeferredWorld::from(world);
if targets.entities().is_empty() {
let mut entity_targets = targets.entities().peekable();
if entity_targets.peek().is_none() {
// SAFETY: T is accessible as the type represented by self.trigger, ensured in `Self::new`
unsafe {
world.trigger_observers_with_data::<_, E::Traversal>(
Expand All @@ -77,12 +78,12 @@ fn trigger_event<E: Event, Targets: TriggerTargets>(
);
};
} else {
for target in targets.entities() {
for target_entity in entity_targets {
// SAFETY: T is accessible as the type represented by self.trigger, ensured in `Self::new`
unsafe {
world.trigger_observers_with_data::<_, E::Traversal>(
event_type,
*target,
target_entity,
targets.components(),
event_data,
E::AUTO_PROPAGATE,
Expand All @@ -100,88 +101,88 @@ fn trigger_event<E: Event, Targets: TriggerTargets>(
/// [`Observer`]: crate::observer::Observer
pub trait TriggerTargets {
/// The components the trigger should target.
fn components(&self) -> &[ComponentId];
fn components(&self) -> impl Iterator<Item = ComponentId> + Clone;

/// The entities the trigger should target.
fn entities(&self) -> &[Entity];
fn entities(&self) -> impl Iterator<Item = Entity>;
}
Comment on lines 110 to 116
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Worth noting that this effectively reverts the change to this trait from #13991 which made it object-safe. I don't see any discussion for that original change, but if it's being changed back, it probably warrants some. At the very least, we should probably go back to the original impl ExactSizeIterator<...> return types if possible to keep it consistent with 0.14.0 and minimize potential for breakage.

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Yes I was hoping to see more discussions on the consequences of this change; I wasn't sure why the change was made in the first place.

Note that impl ExactSizeIterator is unfortunately not possible because calling chain on 2 ExactSizeIterator does not return an ExactSizeIterator

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We could also just provide our own Iterator type to make this object safe

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After digging into #14775, returning Iterators would simplify its implementation. So I'm in favor of this change.


impl TriggerTargets for () {
fn components(&self) -> &[ComponentId] {
&[]
fn components(&self) -> impl Iterator<Item = ComponentId> + Clone {
[].into_iter()
}

fn entities(&self) -> &[Entity] {
&[]
fn entities(&self) -> impl Iterator<Item = Entity> {
[].into_iter()
}
}

impl TriggerTargets for Entity {
fn components(&self) -> &[ComponentId] {
&[]
fn components(&self) -> impl Iterator<Item = ComponentId> + Clone {
[].into_iter()
}

fn entities(&self) -> &[Entity] {
std::slice::from_ref(self)
fn entities(&self) -> impl Iterator<Item = Entity> {
std::iter::once(*self)
}
}

impl TriggerTargets for Vec<Entity> {
fn components(&self) -> &[ComponentId] {
&[]
fn components(&self) -> impl Iterator<Item = ComponentId> + Clone {
[].into_iter()
}

fn entities(&self) -> &[Entity] {
self.as_slice()
fn entities(&self) -> impl Iterator<Item = Entity> {
self.iter().copied()
}
}

impl<const N: usize> TriggerTargets for [Entity; N] {
fn components(&self) -> &[ComponentId] {
&[]
fn components(&self) -> impl Iterator<Item = ComponentId> + Clone {
[].into_iter()
}

fn entities(&self) -> &[Entity] {
self.as_slice()
fn entities(&self) -> impl Iterator<Item = Entity> {
self.iter().copied()
}
}

impl TriggerTargets for ComponentId {
fn components(&self) -> &[ComponentId] {
std::slice::from_ref(self)
fn components(&self) -> impl Iterator<Item = ComponentId> + Clone {
std::iter::once(*self)
}

fn entities(&self) -> &[Entity] {
&[]
fn entities(&self) -> impl Iterator<Item = Entity> {
[].into_iter()
}
}

impl TriggerTargets for Vec<ComponentId> {
fn components(&self) -> &[ComponentId] {
self.as_slice()
fn components(&self) -> impl Iterator<Item = ComponentId> + Clone {
self.iter().copied()
}

fn entities(&self) -> &[Entity] {
&[]
fn entities(&self) -> impl Iterator<Item = Entity> {
[].into_iter()
}
}

impl<const N: usize> TriggerTargets for [ComponentId; N] {
fn components(&self) -> &[ComponentId] {
self.as_slice()
fn components(&self) -> impl Iterator<Item = ComponentId> + Clone {
self.iter().copied()
}

fn entities(&self) -> &[Entity] {
&[]
fn entities(&self) -> impl Iterator<Item = Entity> {
[].into_iter()
}
}

impl TriggerTargets for &Vec<Entity> {
fn components(&self) -> &[ComponentId] {
&[]
impl<T1: TriggerTargets, T2: TriggerTargets> TriggerTargets for (T1, T2) {
fn components(&self) -> impl Iterator<Item = ComponentId> + Clone {
self.0.components().chain(self.1.components())
}

fn entities(&self) -> &[Entity] {
self.as_slice()
fn entities(&self) -> impl Iterator<Item = Entity> {
self.0.entities().chain(self.1.entities())
}
}
4 changes: 2 additions & 2 deletions crates/bevy_ecs/src/world/deferred_world.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -391,7 +391,7 @@ impl<'w> DeferredWorld<'w> {
&mut self,
event: ComponentId,
mut entity: Entity,
components: &[ComponentId],
components: impl Iterator<Item = ComponentId> + Clone,
data: &mut E,
mut propagate: bool,
) where
Expand All @@ -402,7 +402,7 @@ impl<'w> DeferredWorld<'w> {
self.reborrow(),
event,
entity,
components.iter().copied(),
components.clone(),
data,
&mut propagate,
);
Expand Down