Rename Trigger to On

benches/benches/bevy_ecs/observers/propagation.rs

@@ -117,6 +117,6 @@ fn add_listeners_to_hierarchy<const DENSITY: usize, const N: usize>(
     }
 }
 
-fn empty_listener<const N: usize>(trigger: Trigger<TestEvent<N>>) {
+fn empty_listener<const N: usize>(trigger: On<TestEvent<N>>) {
     black_box(trigger);
 }

benches/benches/bevy_ecs/observers/simple.rs

@@ -2,7 +2,7 @@ use core::hint::black_box;
 
 use bevy_ecs::{
     event::Event,
-    observer::{Trigger, TriggerTargets},
+    observer::{On, TriggerTargets},
     world::World,
 };
 
@@ -46,7 +46,7 @@ pub fn observe_simple(criterion: &mut Criterion) {
     group.finish();
 }
 
-fn empty_listener_base(trigger: Trigger<EventBase>) {
+fn empty_listener_base(trigger: On<EventBase>) {
     black_box(trigger);
 }
 

crates/bevy_app/src/app.rs

@@ -1306,7 +1306,7 @@ impl App {
 
     /// Spawns an [`Observer`] entity, which will watch for and respond to the given event.
     ///
-    /// `observer` can be any system whose first parameter is a [`Trigger`].
+    /// `observer` can be any system whose first parameter is [`On`].
     ///
     /// # Examples
     ///
@@ -1329,7 +1329,7 @@ impl App {
     /// # struct Friend;
     /// #
     ///
-    /// app.add_observer(|trigger: Trigger<Party>, friends: Query<Entity, With<Friend>>, mut commands: Commands| {
+    /// app.add_observer(|trigger: On<Party>, friends: Query<Entity, With<Friend>>, mut commands: Commands| {
     ///     if trigger.event().friends_allowed {
     ///         for friend in friends.iter() {
     ///             commands.trigger_targets(Invite, friend);

crates/bevy_core_widgets/src/core_button.rs

@@ -6,7 +6,7 @@ use bevy_ecs::system::ResMut;
 use bevy_ecs::{
     component::Component,
     entity::Entity,
-    observer::Trigger,
+    observer::On,
     query::With,
     system::{Commands, Query, SystemId},
 };
@@ -28,7 +28,7 @@ pub struct CoreButton {
 }
 
 fn button_on_key_event(
-    mut trigger: Trigger<FocusedInput<KeyboardInput>>,
+    mut trigger: On<FocusedInput<KeyboardInput>>,
     q_state: Query<(&CoreButton, Has<InteractionDisabled>)>,
     mut commands: Commands,
 ) {
@@ -48,7 +48,7 @@ fn button_on_key_event(
 }
 
 fn button_on_pointer_click(
-    mut trigger: Trigger<Pointer<Click>>,
+    mut trigger: On<Pointer<Click>>,
     mut q_state: Query<(&CoreButton, Has<Pressed>, Has<InteractionDisabled>)>,
     mut commands: Commands,
 ) {
@@ -63,7 +63,7 @@ fn button_on_pointer_click(
 }
 
 fn button_on_pointer_down(
-    mut trigger: Trigger<Pointer<Press>>,
+    mut trigger: On<Pointer<Press>>,
     mut q_state: Query<(Entity, Has<InteractionDisabled>, Has<Pressed>), With<CoreButton>>,
     focus: Option<ResMut<InputFocus>>,
     focus_visible: Option<ResMut<InputFocusVisible>>,
@@ -88,7 +88,7 @@ fn button_on_pointer_down(
 }
 
 fn button_on_pointer_up(
-    mut trigger: Trigger<Pointer<Release>>,
+    mut trigger: On<Pointer<Release>>,
     mut q_state: Query<(Entity, Has<InteractionDisabled>, Has<Pressed>), With<CoreButton>>,
     mut commands: Commands,
 ) {
@@ -101,7 +101,7 @@ fn button_on_pointer_up(
 }
 
 fn button_on_pointer_drag_end(
-    mut trigger: Trigger<Pointer<DragEnd>>,
+    mut trigger: On<Pointer<DragEnd>>,
     mut q_state: Query<(Entity, Has<InteractionDisabled>, Has<Pressed>), With<CoreButton>>,
     mut commands: Commands,
 ) {
@@ -114,7 +114,7 @@ fn button_on_pointer_drag_end(
 }
 
 fn button_on_pointer_cancel(
-    mut trigger: Trigger<Pointer<Cancel>>,
+    mut trigger: On<Pointer<Cancel>>,
     mut q_state: Query<(Entity, Has<InteractionDisabled>, Has<Pressed>), With<CoreButton>>,
     mut commands: Commands,
 ) {

crates/bevy_ecs/README.md

@@ -315,7 +315,7 @@ struct MyEvent {
 
 let mut world = World::new();
 
-world.add_observer(|trigger: Trigger<MyEvent>| {
+world.add_observer(|trigger: On<MyEvent>| {
     println!("{}", trigger.event().message);
 });
 
@@ -339,7 +339,7 @@ struct Explode;
 let mut world = World::new();
 let entity = world.spawn_empty().id();
 
-world.add_observer(|trigger: Trigger<Explode>, mut commands: Commands| {
+world.add_observer(|trigger: On<Explode>, mut commands: Commands| {
     println!("Entity {} goes BOOM!", trigger.target().unwrap());
     commands.entity(trigger.target().unwrap()).despawn();
 });

crates/bevy_ecs/src/archetype.rs

@@ -691,41 +691,41 @@ impl Archetype {
         self.flags().contains(ArchetypeFlags::ON_DESPAWN_HOOK)
     }
 
-    /// Returns true if any of the components in this archetype have at least one [`OnAdd`] observer
+    /// Returns true if any of the components in this archetype have at least one [`Add`] observer
     ///
-    /// [`OnAdd`]: crate::lifecycle::OnAdd
+    /// [`Add`]: crate::lifecycle::Add
     #[inline]
     pub fn has_add_observer(&self) -> bool {
         self.flags().contains(ArchetypeFlags::ON_ADD_OBSERVER)
     }
 
-    /// Returns true if any of the components in this archetype have at least one [`OnInsert`] observer
+    /// Returns true if any of the components in this archetype have at least one [`Insert`] observer
     ///
-    /// [`OnInsert`]: crate::lifecycle::OnInsert
+    /// [`Insert`]: crate::lifecycle::Insert
     #[inline]
     pub fn has_insert_observer(&self) -> bool {
         self.flags().contains(ArchetypeFlags::ON_INSERT_OBSERVER)
     }
 
-    /// Returns true if any of the components in this archetype have at least one [`OnReplace`] observer
+    /// Returns true if any of the components in this archetype have at least one [`Replace`] observer
     ///
-    /// [`OnReplace`]: crate::lifecycle::OnReplace
+    /// [`Replace`]: crate::lifecycle::Replace
     #[inline]
     pub fn has_replace_observer(&self) -> bool {
         self.flags().contains(ArchetypeFlags::ON_REPLACE_OBSERVER)
     }
 
-    /// Returns true if any of the components in this archetype have at least one [`OnRemove`] observer
+    /// Returns true if any of the components in this archetype have at least one [`Remove`] observer
     ///
-    /// [`OnRemove`]: crate::lifecycle::OnRemove
+    /// [`Remove`]: crate::lifecycle::Remove
     #[inline]
     pub fn has_remove_observer(&self) -> bool {
         self.flags().contains(ArchetypeFlags::ON_REMOVE_OBSERVER)
     }
 
-    /// Returns true if any of the components in this archetype have at least one [`OnDespawn`] observer
+    /// Returns true if any of the components in this archetype have at least one [`Despawn`] observer
     ///
-    /// [`OnDespawn`]: crate::lifecycle::OnDespawn
+    /// [`Despawn`]: crate::lifecycle::Despawn
     #[inline]
     pub fn has_despawn_observer(&self) -> bool {
         self.flags().contains(ArchetypeFlags::ON_DESPAWN_OBSERVER)

crates/bevy_ecs/src/bundle.rs

@@ -66,7 +66,7 @@ use crate::{
         RequiredComponents, StorageType, Tick,
     },
     entity::{Entities, Entity, EntityLocation},
-    lifecycle::{ON_ADD, ON_INSERT, ON_REMOVE, ON_REPLACE},
+    lifecycle::{ADD, INSERT, REMOVE, REPLACE},
     observer::Observers,
     prelude::World,
     query::DebugCheckedUnwrap,
@@ -1191,7 +1191,7 @@ impl<'w> BundleInserter<'w> {
             if insert_mode == InsertMode::Replace {
                 if archetype.has_replace_observer() {
                     deferred_world.trigger_observers(
-                        ON_REPLACE,
+                        REPLACE,
                         Some(entity),
                         archetype_after_insert.iter_existing(),
                         caller,
@@ -1376,7 +1376,7 @@ impl<'w> BundleInserter<'w> {
             );
             if new_archetype.has_add_observer() {
                 deferred_world.trigger_observers(
-                    ON_ADD,
+                    ADD,
                     Some(entity),
                     archetype_after_insert.iter_added(),
                     caller,
@@ -1394,7 +1394,7 @@ impl<'w> BundleInserter<'w> {
                     );
                     if new_archetype.has_insert_observer() {
                         deferred_world.trigger_observers(
-                            ON_INSERT,
+                            INSERT,
                             Some(entity),
                             archetype_after_insert.iter_inserted(),
                             caller,
@@ -1413,7 +1413,7 @@ impl<'w> BundleInserter<'w> {
                     );
                     if new_archetype.has_insert_observer() {
                         deferred_world.trigger_observers(
-                            ON_INSERT,
+                            INSERT,
                             Some(entity),
                             archetype_after_insert.iter_added(),
                             caller,
@@ -1567,7 +1567,7 @@ impl<'w> BundleRemover<'w> {
             };
             if self.old_archetype.as_ref().has_replace_observer() {
                 deferred_world.trigger_observers(
-                    ON_REPLACE,
+                    REPLACE,
                     Some(entity),
                     bundle_components_in_archetype(),
                     caller,
@@ -1582,7 +1582,7 @@ impl<'w> BundleRemover<'w> {
             );
             if self.old_archetype.as_ref().has_remove_observer() {
                 deferred_world.trigger_observers(
-                    ON_REMOVE,
+                    REMOVE,
                     Some(entity),
                     bundle_components_in_archetype(),
                     caller,
@@ -1833,7 +1833,7 @@ impl<'w> BundleSpawner<'w> {
             );
             if archetype.has_add_observer() {
                 deferred_world.trigger_observers(
-                    ON_ADD,
+                    ADD,
                     Some(entity),
                     bundle_info.iter_contributed_components(),
                     caller,
@@ -1848,7 +1848,7 @@ impl<'w> BundleSpawner<'w> {
             );
             if archetype.has_insert_observer() {
                 deferred_world.trigger_observers(
-                    ON_INSERT,
+                    INSERT,
                     Some(entity),
                     bundle_info.iter_contributed_components(),
                     caller,
@@ -2386,7 +2386,7 @@ mod tests {
         #[derive(Resource, Default)]
         struct Count(u32);
         world.init_resource::<Count>();
-        world.add_observer(|_t: Trigger<ArchetypeCreated>, mut count: ResMut<Count>| {
+        world.add_observer(|_t: On<ArchetypeCreated>, mut count: ResMut<Count>| {
             count.0 += 1;
         });
 

crates/bevy_ecs/src/component.rs

@@ -598,7 +598,7 @@ mod private {
 /// `&mut ...`, created while inserted onto an entity.
 /// In all other ways, they are identical to mutable components.
 /// This restriction allows hooks to observe all changes made to an immutable
-/// component, effectively turning the `OnInsert` and `OnReplace` hooks into a
+/// component, effectively turning the `Insert` and `Replace` hooks into a
 /// `OnMutate` hook.
 /// This is not practical for mutable components, as the runtime cost of invoking
 /// a hook for every exclusive reference created would be far too high.
@@ -2415,7 +2415,7 @@ impl Tick {
 /// struct CustomSchedule(Schedule);
 ///
 /// # let mut world = World::new();
-/// world.add_observer(|tick: Trigger<CheckChangeTicks>, mut schedule: ResMut<CustomSchedule>| {
+/// world.add_observer(|tick: On<CheckChangeTicks>, mut schedule: ResMut<CustomSchedule>| {
 ///     schedule.0.check_change_ticks(tick.get());
 /// });
 /// ```

crates/bevy_ecs/src/event/base.rs

@@ -46,16 +46,17 @@ use core::{
     note = "consider annotating `{Self}` with `#[derive(Event)]`"
 )]
 pub trait Event: Send + Sync + 'static {
-    /// The component that describes which Entity to propagate this event to next, when [propagation] is enabled.
+    /// The component that describes which [`Entity`] to propagate this event to next, when [propagation] is enabled.
     ///
-    /// [propagation]: crate::observer::Trigger::propagate
+    /// [`Entity`]: crate::entity::Entity
+    /// [propagation]: crate::observer::On::propagate
     type Traversal: Traversal<Self>;
 
     /// When true, this event will always attempt to propagate when [triggered], without requiring a call
-    /// to [`Trigger::propagate`].
+    /// to [`On::propagate`].
     ///
     /// [triggered]: crate::system::Commands::trigger_targets
-    /// [`Trigger::propagate`]: crate::observer::Trigger::propagate
+    /// [`On::propagate`]: crate::observer::On::propagate
     const AUTO_PROPAGATE: bool = false;
 
     /// Generates the [`ComponentId`] for this event type.

crates/bevy_ecs/src/lib.rs

@@ -67,6 +67,10 @@ use event::Event;
 /// This includes the most common types in this crate, re-exported for your convenience.
 pub mod prelude {
     #[doc(hidden)]
+    #[expect(
+        deprecated,
+        reason = "`Trigger` was deprecated in favor of `On`, and `OnX` lifecycle events were deprecated in favor of `X` events."
+    )]
     pub use crate::{
         bundle::Bundle,
         change_detection::{DetectChanges, DetectChangesMut, Mut, Ref},
@@ -76,9 +80,12 @@ pub mod prelude {
         error::{BevyError, Result},
         event::{Event, EventMutator, EventReader, EventWriter, Events},
         hierarchy::{ChildOf, ChildSpawner, ChildSpawnerCommands, Children},
-        lifecycle::{OnAdd, OnDespawn, OnInsert, OnRemove, OnReplace, RemovedComponents},
+        lifecycle::{
+            Add, Despawn, Insert, OnAdd, OnDespawn, OnInsert, OnRemove, OnReplace, Remove,
+            RemovedComponents, Replace,
+        },
         name::{Name, NameOrEntity},
-        observer::{Observer, Trigger},
+        observer::{Observer, On, Trigger},
         query::{Added, Allows, AnyOf, Changed, Has, Or, QueryBuilder, QueryState, With, Without},
         related,
         relationship::RelationshipTarget,