Merge 43960f69d9 into 877d278785

crates/bevy_scene/src/lib.rs

@@ -91,12 +91,19 @@ impl Plugin for ScenePlugin {
         app.world_mut()
             .register_component_hooks::<SceneRoot>()
             .on_remove(|mut world, context| {
+                let Some(handle) = world.get::<SceneRoot>(context.entity) else {
+                    return;
+                };
+                let id = handle.id();
                 if let Some(&SceneInstance(scene_instance)) =
                     world.get::<SceneInstance>(context.entity)
                 {
                     let Some(mut scene_spawner) = world.get_resource_mut::<SceneSpawner>() else {
                         return;
                     };
+                    if let Some(instance_ids) = scene_spawner.spawned_scenes.get_mut(&id) {
+                        instance_ids.remove(&scene_instance);
+                    }
                     scene_spawner.unregister_instance(scene_instance);
                 }
             });
@@ -107,3 +114,299 @@ impl Plugin for ScenePlugin {
 impl Plugin for ScenePlugin {
     fn build(&self, _: &mut App) {}
 }
+
+#[cfg(test)]
+mod tests {
+    use bevy_app::App;
+    use bevy_asset::{AssetPlugin, Assets};
+    use bevy_ecs::{
+        component::Component,
+        hierarchy::{ChildOf, Children},
+        reflect::{AppTypeRegistry, ReflectComponent},
+        world::World,
+    };
+    use bevy_reflect::Reflect;
+
+    use crate::{
+        DynamicScene, DynamicSceneBuilder, DynamicSceneRoot, Scene, ScenePlugin, SceneRoot,
+    };
+
+    #[derive(Component, Reflect, PartialEq, Debug)]
+    #[reflect(Component)]
+    struct Circle {
+        radius: f32,
+    }
+
+    #[derive(Component, Reflect, PartialEq, Debug)]
+    #[reflect(Component)]
+    struct Rectangle {
+        width: f32,
+        height: f32,
+    }
+
+    #[derive(Component, Reflect, PartialEq, Debug)]
+    #[reflect(Component)]
+    struct Triangle {
+        base: f32,
+        height: f32,
+    }
+
+    #[derive(Component, Reflect)]
+    #[reflect(Component)]
+    struct FinishLine;
+
+    #[test]
+    fn scene_spawns_and_respawns_after_change() {
+        let mut app = App::new();
+
+        app.add_plugins((AssetPlugin::default(), ScenePlugin))
+            .register_type::<Circle>()
+            .register_type::<Rectangle>()
+            .register_type::<Triangle>()
+            .register_type::<FinishLine>();
+
+        let scene_handle = app
+            .world_mut()
+            .resource_mut::<Assets<Scene>>()
+            .reserve_handle();
+
+        let scene_entity = app.world_mut().spawn(SceneRoot(scene_handle.clone())).id();
+        app.update();
+
+        assert!(app.world().entity(scene_entity).get::<Children>().is_none());
+
+        let mut scene_1 = Scene {
+            world: World::new(),
+        };
+        let root = scene_1.world.spawn_empty().id();
+        scene_1.world.spawn((
+            Rectangle {
+                width: 10.0,
+                height: 5.0,
+            },
+            FinishLine,
+            ChildOf(root),
+        ));
+        scene_1.world.spawn((Circle { radius: 7.0 }, ChildOf(root)));
+
+        app.world_mut()
+            .resource_mut::<Assets<Scene>>()
+            .insert(&scene_handle, scene_1);
+
+        app.update();
+
+        let child_root = app
+            .world()
+            .entity(scene_entity)
+            .get::<Children>()
+            .and_then(|children| children.first().cloned())
+            .expect("There should be exactly one child on the scene root");
+        let children = app
+            .world()
+            .entity(child_root)
+            .get::<Children>()
+            .expect("The child of the scene root should itself have 2 children");
+        assert_eq!(children.len(), 2);
+
+        let finish_line = app.world().entity(children[0]);
+        assert_eq!(finish_line.archetype().component_count(), 3);
+        let (rectangle, _, child_of) =
+            finish_line.components::<(&Rectangle, &FinishLine, &ChildOf)>();
+        assert_eq!(
+            rectangle,
+            &Rectangle {
+                width: 10.0,
+                height: 5.0,
+            }
+        );
+        assert_eq!(child_of.0, child_root);
+
+        let circle = app.world().entity(children[1]);
+        assert_eq!(circle.archetype().component_count(), 2);
+        let (circle, child_of) = circle.components::<(&Circle, &ChildOf)>();
+        assert_eq!(circle, &Circle { radius: 7.0 });
+        assert_eq!(child_of.0, child_root);
+
+        // Now that we know our scene contains exactly what we expect, we will change the scene
+        // asset and ensure it contains the new scene results.
+
+        let mut scene_2 = Scene {
+            world: World::new(),
+        };
+        let root = scene_2.world.spawn_empty().id();
+        scene_2.world.spawn((
+            Triangle {
+                base: 1.0,
+                height: 2.0,
+            },
+            ChildOf(root),
+        ));
+
+        app.world_mut()
+            .resource_mut::<Assets<Scene>>()
+            .insert(&scene_handle, scene_2);
+
+        app.update();
+        app.update();
+
+        let child_root = app
+            .world()
+            .entity(scene_entity)
+            .get::<Children>()
+            .and_then(|children| children.first().cloned())
+            .expect("There should be exactly one child on the scene root");
+        let children = app
+            .world()
+            .entity(child_root)
+            .get::<Children>()
+            .expect("The child of the scene root should itself have 2 children");
+        assert_eq!(children.len(), 1);
+
+        let triangle = app.world().entity(children[0]);
+        assert_eq!(triangle.archetype().component_count(), 2);
+        let (triangle, child_of) = triangle.components::<(&Triangle, &ChildOf)>();
+        assert_eq!(
+            triangle,
+            &Triangle {
+                base: 1.0,
+                height: 2.0,
+            }
+        );
+        assert_eq!(child_of.0, child_root);
+    }
+
+    #[test]
+    fn dynamic_scene_spawns_and_respawns_after_change() {
+        let mut app = App::new();
+
+        app.add_plugins((AssetPlugin::default(), ScenePlugin))
+            .register_type::<Circle>()
+            .register_type::<Rectangle>()
+            .register_type::<Triangle>()
+            .register_type::<FinishLine>();
+
+        let scene_handle = app
+            .world_mut()
+            .resource_mut::<Assets<DynamicScene>>()
+            .reserve_handle();
+
+        let scene_entity = app
+            .world_mut()
+            .spawn(DynamicSceneRoot(scene_handle.clone()))
+            .id();
+        app.update();
+
+        assert!(app.world().entity(scene_entity).get::<Children>().is_none());
+
+        let create_dynamic_scene = |mut scene: Scene, world: &World| {
+            scene
+                .world
+                .insert_resource(world.resource::<AppTypeRegistry>().clone());
+            DynamicSceneBuilder::from_world(&scene.world)
+                .extract_entities(scene.world.iter_entities().map(|entity| entity.id()))
+                .build()
+        };
+
+        let mut scene_1 = Scene {
+            world: World::new(),
+        };
+        let root = scene_1.world.spawn_empty().id();
+        scene_1.world.spawn((
+            Rectangle {
+                width: 10.0,
+                height: 5.0,
+            },
+            FinishLine,
+            ChildOf(root),
+        ));
+        scene_1.world.spawn((Circle { radius: 7.0 }, ChildOf(root)));
+
+        let scene_1 = create_dynamic_scene(scene_1, app.world());
+        app.world_mut()
+            .resource_mut::<Assets<DynamicScene>>()
+            .insert(&scene_handle, scene_1);
+
+        app.update();
+
+        let child_root = app
+            .world()
+            .entity(scene_entity)
+            .get::<Children>()
+            .and_then(|children| children.first().cloned())
+            .expect("There should be exactly one child on the scene root");
+        let children = app
+            .world()
+            .entity(child_root)
+            .get::<Children>()
+            .expect("The child of the scene root should itself have 2 children");
+        assert_eq!(children.len(), 2);
+
+        let finish_line = app.world().entity(children[0]);
+        assert_eq!(finish_line.archetype().component_count(), 3);
+        let (rectangle, _, child_of) =
+            finish_line.components::<(&Rectangle, &FinishLine, &ChildOf)>();
+        assert_eq!(
+            rectangle,
+            &Rectangle {
+                width: 10.0,
+                height: 5.0,
+            }
+        );
+        assert_eq!(child_of.0, child_root);
+
+        let circle = app.world().entity(children[1]);
+        assert_eq!(circle.archetype().component_count(), 2);
+        let (circle, child_of) = circle.components::<(&Circle, &ChildOf)>();
+        assert_eq!(circle, &Circle { radius: 7.0 });
+        assert_eq!(child_of.0, child_root);
+
+        // Now that we know our scene contains exactly what we expect, we will change the scene
+        // asset and ensure it contains the new scene results.
+
+        let mut scene_2 = Scene {
+            world: World::new(),
+        };
+        let root = scene_2.world.spawn_empty().id();
+        scene_2.world.spawn((
+            Triangle {
+                base: 1.0,
+                height: 2.0,
+            },
+            ChildOf(root),
+        ));
+
+        let scene_2 = create_dynamic_scene(scene_2, app.world());
+
+        app.world_mut()
+            .resource_mut::<Assets<DynamicScene>>()
+            .insert(&scene_handle, scene_2);
+
+        app.update();
+        app.update();
+
+        let child_root = app
+            .world()
+            .entity(scene_entity)
+            .get::<Children>()
+            .and_then(|children| children.first().cloned())
+            .expect("There should be exactly one child on the scene root");
+        let children = app
+            .world()
+            .entity(child_root)
+            .get::<Children>()
+            .expect("The child of the scene root should itself have 2 children");
+        assert_eq!(children.len(), 1);
+
+        let triangle = app.world().entity(children[0]);
+        assert_eq!(triangle.archetype().component_count(), 2);
+        let (triangle, child_of) = triangle.components::<(&Triangle, &ChildOf)>();
+        assert_eq!(
+            triangle,
+            &Triangle {
+                base: 1.0,
+                height: 2.0,
+            }
+        );
+        assert_eq!(child_of.0, child_root);
+    }
+}

crates/bevy_scene/src/scene_spawner.rs

@@ -36,9 +36,11 @@ pub struct SceneInstanceReady {
 
 /// Information about a scene instance.
 #[derive(Debug)]
-pub struct InstanceInfo {
+struct InstanceInfo {
     /// Mapping of entities from the scene world to the instance world.
-    pub entity_map: EntityHashMap<Entity>,
+    entity_map: EntityHashMap<Entity>,
+    /// The parent to attach this instance to.
+    parent: Option<Entity>,
 }
 
 /// Unique id identifying a scene instance.
@@ -55,11 +57,13 @@ impl InstanceId {
 /// Handles spawning and despawning scenes in the world, either synchronously or batched through the [`scene_spawner_system`].
 ///
 /// Synchronous methods: (Scene operations will take effect immediately)
-/// - [`spawn_dynamic_sync`](Self::spawn_dynamic_sync)
 /// - [`spawn_sync`](Self::spawn_sync)
+/// - [`spawn_dynamic_sync`](Self::spawn_dynamic_sync)
 /// - [`despawn_sync`](Self::despawn_sync)
+/// - [`despawn_dynamic_sync`](Self::despawn_dynamic_sync)
 /// - [`despawn_instance_sync`](Self::despawn_instance_sync)
 /// - [`update_spawned_scenes`](Self::update_spawned_scenes)
+/// - [`update_spawned_dynamic_scenes`](Self::update_spawned_dynamic_scenes)
 /// - [`spawn_queued_scenes`](Self::spawn_queued_scenes)
 /// - [`despawn_queued_scenes`](Self::despawn_queued_scenes)
 /// - [`despawn_queued_instances`](Self::despawn_queued_instances)
@@ -70,17 +74,20 @@ impl InstanceId {
 /// - [`spawn`](Self::spawn)
 /// - [`spawn_as_child`](Self::spawn_as_child)
 /// - [`despawn`](Self::despawn)
+/// - [`despawn_dynamic`](Self::despawn_dynamic)
 /// - [`despawn_instance`](Self::despawn_instance)
 #[derive(Default, Resource)]
 pub struct SceneSpawner {
+    pub(crate) spawned_scenes: HashMap<AssetId<Scene>, HashSet<InstanceId>>,
     pub(crate) spawned_dynamic_scenes: HashMap<AssetId<DynamicScene>, HashSet<InstanceId>>,
-    pub(crate) spawned_instances: HashMap<InstanceId, InstanceInfo>,
-    scene_asset_event_reader: EventCursor<AssetEvent<DynamicScene>>,
-    dynamic_scenes_to_spawn: Vec<(Handle<DynamicScene>, InstanceId, Option<Entity>)>,
+    spawned_instances: HashMap<InstanceId, InstanceInfo>,
+    scene_asset_event_reader: EventCursor<AssetEvent<Scene>>,
+    dynamic_scene_asset_event_reader: EventCursor<AssetEvent<DynamicScene>>,
     scenes_to_spawn: Vec<(Handle<Scene>, InstanceId, Option<Entity>)>,
-    scenes_to_despawn: Vec<AssetId<DynamicScene>>,
+    dynamic_scenes_to_spawn: Vec<(Handle<DynamicScene>, InstanceId, Option<Entity>)>,
+    scenes_to_despawn: Vec<AssetId<Scene>>,
+    dynamic_scenes_to_despawn: Vec<AssetId<DynamicScene>>,
     instances_to_despawn: Vec<InstanceId>,
-    scenes_with_parent: Vec<(InstanceId, Entity)>,
     instances_ready: Vec<(InstanceId, Option<Entity>)>,
 }
 
@@ -156,7 +163,6 @@ impl SceneSpawner {
         let instance_id = InstanceId::new();
         self.dynamic_scenes_to_spawn
             .push((id.into(), instance_id, Some(parent)));
-        self.scenes_with_parent.push((instance_id, parent));
         instance_id
     }
 
@@ -172,15 +178,19 @@ impl SceneSpawner {
         let instance_id = InstanceId::new();
         self.scenes_to_spawn
             .push((id.into(), instance_id, Some(parent)));
-        self.scenes_with_parent.push((instance_id, parent));
         instance_id
     }
 
-    /// Schedule the despawn of all instances of the provided dynamic scene.
-    pub fn despawn(&mut self, id: impl Into<AssetId<DynamicScene>>) {
+    /// Schedule the despawn of all instances of the provided scene.
+    pub fn despawn(&mut self, id: impl Into<AssetId<Scene>>) {
         self.scenes_to_despawn.push(id.into());
     }
 
+    /// Schedule the despawn of all instances of the provided dynamic scene.
+    pub fn despawn_dynamic(&mut self, id: impl Into<AssetId<DynamicScene>>) {
+        self.dynamic_scenes_to_despawn.push(id.into());
+    }
+
     /// Schedule the despawn of a scene instance, removing all its entities from the world.
     ///
     /// Note: this will despawn _all_ entities associated with this instance, including those
@@ -195,8 +205,22 @@ impl SceneSpawner {
         self.spawned_instances.remove(&instance_id);
     }
 
-    /// Immediately despawns all instances of a dynamic scene.
+    /// Immediately despawns all instances of a scene.
     pub fn despawn_sync(
+        &mut self,
+        world: &mut World,
+        id: impl Into<AssetId<Scene>>,
+    ) -> Result<(), SceneSpawnError> {
+        if let Some(instance_ids) = self.spawned_scenes.remove(&id.into()) {
+            for instance_id in instance_ids {
+                self.despawn_instance_sync(world, &instance_id);
+            }
+        }
+        Ok(())
+    }
+
+    /// Immediately despawns all instances of a dynamic scene.
+    pub fn despawn_dynamic_sync(
         &mut self,
         world: &mut World,
         id: impl Into<AssetId<DynamicScene>>,
@@ -211,15 +235,21 @@ impl SceneSpawner {
 
     /// Immediately despawns a scene instance, removing all its entities from the world.
     pub fn despawn_instance_sync(&mut self, world: &mut World, instance_id: &InstanceId) {
-        if let Some(instance) = self.spawned_instances.remove(instance_id) {
-            for &entity in instance.entity_map.values() {
-                if let Ok(entity_mut) = world.get_entity_mut(entity) {
-                    entity_mut.despawn();
-                };
-            }
+        if let Some(mut instance) = self.spawned_instances.remove(instance_id) {
+            Self::despawn_instance_internal(world, &mut instance);
         }
     }
 
+    fn despawn_instance_internal(world: &mut World, instance: &mut InstanceInfo) {
+        for &entity in instance.entity_map.values() {
+            if let Ok(entity_mut) = world.get_entity_mut(entity) {
+                entity_mut.despawn();
+            };
+        }
+        // Just make sure if we reuse `InstanceInfo` for something, we don't reuse the despawned entities.
+        instance.entity_map.clear();
+    }
+
     /// Immediately spawns a new instance of the provided dynamic scene.
     pub fn spawn_dynamic_sync(
         &mut self,
@@ -230,10 +260,18 @@ impl SceneSpawner {
         let id = id.into();
         Self::spawn_dynamic_internal(world, id, &mut entity_map)?;
         let instance_id = InstanceId::new();
-        self.spawned_instances
-            .insert(instance_id, InstanceInfo { entity_map });
+        self.spawned_instances.insert(
+            instance_id,
+            InstanceInfo {
+                entity_map,
+                parent: None,
+            },
+        );
         let spawned = self.spawned_dynamic_scenes.entry(id).or_default();
         spawned.insert(instance_id);
+        // We trigger `SceneInstanceReady` events after processing all scenes
+        // SceneSpawner may not be available in the observer.
+        self.instances_ready.push((instance_id, None));
         Ok(instance_id)
     }
 
@@ -261,8 +299,18 @@ impl SceneSpawner {
         let id = id.into();
         Self::spawn_sync_internal(world, id, &mut entity_map)?;
         let instance_id = InstanceId::new();
-        self.spawned_instances
-            .insert(instance_id, InstanceInfo { entity_map });
+        self.spawned_instances.insert(
+            instance_id,
+            InstanceInfo {
+                entity_map,
+                parent: None,
+            },
+        );
+        let spawned = self.spawned_scenes.entry(id).or_default();
+        spawned.insert(instance_id);
+        // We trigger `SceneInstanceReady` events after processing all scenes
+        // SceneSpawner may not be available in the observer.
+        self.instances_ready.push((instance_id, None));
         Ok(instance_id)
     }
 
@@ -286,8 +334,39 @@ impl SceneSpawner {
 
     /// Iterate through all instances of the provided scenes and update those immediately.
     ///
-    /// Useful for updating already spawned scene instances after their corresponding scene has been modified.
+    /// Useful for updating already spawned scene instances after their corresponding scene has been
+    /// modified.
     pub fn update_spawned_scenes(
+        &mut self,
+        world: &mut World,
+        scene_ids: &[AssetId<Scene>],
+    ) -> Result<(), SceneSpawnError> {
+        for id in scene_ids {
+            if let Some(spawned_instances) = self.spawned_scenes.get(id) {
+                for instance_id in spawned_instances {
+                    if let Some(instance_info) = self.spawned_instances.get_mut(instance_id) {
+                        // Despawn the scene before respawning it. This is a very heavy operation,
+                        // but otherwise, entities may be left behind, or be left in an otherwise
+                        // invalid state (e.g., invalid relationships).
+                        Self::despawn_instance_internal(world, instance_info);
+                        Self::spawn_sync_internal(world, *id, &mut instance_info.entity_map)?;
+                        Self::set_scene_instance_parent_sync(world, instance_info);
+                        // We trigger `SceneInstanceReady` events after processing all scenes
+                        // SceneSpawner may not be available in the observer.
+                        self.instances_ready
+                            .push((*instance_id, instance_info.parent));
+                    }
+                }
+            }
+        }
+        Ok(())
+    }
+
+    /// Iterate through all instances of the provided dynamic scenes and update those immediately.
+    ///
+    /// Useful for updating already spawned scene instances after their corresponding dynamic scene
+    /// has been modified.
+    pub fn update_spawned_dynamic_scenes(
         &mut self,
         world: &mut World,
         scene_ids: &[AssetId<DynamicScene>],
@@ -296,7 +375,16 @@ impl SceneSpawner {
             if let Some(spawned_instances) = self.spawned_dynamic_scenes.get(id) {
                 for instance_id in spawned_instances {
                     if let Some(instance_info) = self.spawned_instances.get_mut(instance_id) {
+                        // Despawn the scene before respawning it. This is a very heavy operation,
+                        // but otherwise, entities may be left behind, or be left in an otherwise
+                        // invalid state (e.g., invalid relationships).
+                        Self::despawn_instance_internal(world, instance_info);
                         Self::spawn_dynamic_internal(world, *id, &mut instance_info.entity_map)?;
+                        Self::set_scene_instance_parent_sync(world, instance_info);
+                        // We trigger `SceneInstanceReady` events after processing all scenes
+                        // SceneSpawner may not be available in the observer.
+                        self.instances_ready
+                            .push((*instance_id, instance_info.parent));
                     }
                 }
             }
@@ -307,10 +395,13 @@ impl SceneSpawner {
     /// Immediately despawns all scenes scheduled for despawn by despawning their instances.
     pub fn despawn_queued_scenes(&mut self, world: &mut World) -> Result<(), SceneSpawnError> {
         let scenes_to_despawn = core::mem::take(&mut self.scenes_to_despawn);
-
         for scene_handle in scenes_to_despawn {
             self.despawn_sync(world, scene_handle)?;
         }
+        let scenes_to_despawn = core::mem::take(&mut self.dynamic_scenes_to_despawn);
+        for scene_handle in scenes_to_despawn {
+            self.despawn_dynamic_sync(world, scene_handle)?;
+        }
         Ok(())
     }
 
@@ -332,18 +423,15 @@ impl SceneSpawner {
 
             match Self::spawn_dynamic_internal(world, handle.id(), &mut entity_map) {
                 Ok(_) => {
-                    self.spawned_instances
-                        .insert(instance_id, InstanceInfo { entity_map });
+                    let instance_info = InstanceInfo { entity_map, parent };
+                    Self::set_scene_instance_parent_sync(world, &instance_info);
+
+                    self.spawned_instances.insert(instance_id, instance_info);
                     let spawned = self.spawned_dynamic_scenes.entry(handle.id()).or_default();
                     spawned.insert(instance_id);
-
-                    // Scenes with parents need more setup before they are ready.
-                    // See `set_scene_instance_parent_sync()`.
-                    if parent.is_none() {
-                        // We trigger `SceneInstanceReady` events after processing all scenes
-                        // SceneSpawner may not be available in the observer.
-                        self.instances_ready.push((instance_id, None));
-                    }
+                    // We trigger `SceneInstanceReady` events after processing all scenes
+                    // SceneSpawner may not be available in the observer.
+                    self.instances_ready.push((instance_id, parent));
                 }
                 Err(SceneSpawnError::NonExistentScene { .. }) => {
                     self.dynamic_scenes_to_spawn
@@ -360,16 +448,16 @@ impl SceneSpawner {
 
             match Self::spawn_sync_internal(world, scene_handle.id(), &mut entity_map) {
                 Ok(_) => {
-                    self.spawned_instances
-                        .insert(instance_id, InstanceInfo { entity_map });
+                    let instance_info = InstanceInfo { entity_map, parent };
+                    Self::set_scene_instance_parent_sync(world, &instance_info);
 
-                    // Scenes with parents need more setup before they are ready.
-                    // See `set_scene_instance_parent_sync()`.
-                    if parent.is_none() {
-                        // We trigger `SceneInstanceReady` events after processing all scenes
-                        // SceneSpawner may not be available in the observer.
-                        self.instances_ready.push((instance_id, None));
-                    }
+                    self.spawned_instances.insert(instance_id, instance_info);
+                    let spawned = self.spawned_scenes.entry(scene_handle.id()).or_default();
+                    spawned.insert(instance_id);
+
+                    // We trigger `SceneInstanceReady` events after processing all scenes
+                    // SceneSpawner may not be available in the observer.
+                    self.instances_ready.push((instance_id, parent));
                 }
                 Err(SceneSpawnError::NonExistentRealScene { .. }) => {
                     self.scenes_to_spawn
@@ -382,32 +470,23 @@ impl SceneSpawner {
         Ok(())
     }
 
-    pub(crate) fn set_scene_instance_parent_sync(&mut self, world: &mut World) {
-        let scenes_with_parent = core::mem::take(&mut self.scenes_with_parent);
-
-        for (instance_id, parent) in scenes_with_parent {
-            if let Some(instance) = self.spawned_instances.get(&instance_id) {
-                for &entity in instance.entity_map.values() {
-                    // Add the `ChildOf` component to the scene root, and update the `Children` component of
-                    // the scene parent
-                    if !world
-                        .get_entity(entity)
-                        .ok()
-                        // This will filter only the scene root entity, as all other from the
-                        // scene have a parent
-                        // Entities that wouldn't exist anymore are also skipped
-                        // this case shouldn't happen anyway
-                        .is_none_or(|entity| entity.contains::<ChildOf>())
-                    {
-                        world.entity_mut(parent).add_child(entity);
-                    }
-                }
-
-                // We trigger `SceneInstanceReady` events after processing all scenes
-                // SceneSpawner may not be available in the observer.
-                self.instances_ready.push((instance_id, Some(parent)));
-            } else {
-                self.scenes_with_parent.push((instance_id, parent));
+    fn set_scene_instance_parent_sync(world: &mut World, instance: &InstanceInfo) {
+        let Some(parent) = instance.parent else {
+            return;
+        };
+        for &entity in instance.entity_map.values() {
+            // Add the `ChildOf` component to the scene root, and update the `Children` component of
+            // the scene parent
+            if !world
+                .get_entity(entity)
+                .ok()
+                // This will filter only the scene root entity, as all other from the
+                // scene have a parent
+                // Entities that wouldn't exist anymore are also skipped
+                // this case shouldn't happen anyway
+                .is_none_or(|entity| entity.contains::<ChildOf>())
+            {
+                world.entity_mut(parent).add_child(entity);
             }
         }
     }
@@ -452,39 +531,44 @@ impl SceneSpawner {
 pub fn scene_spawner_system(world: &mut World) {
     world.resource_scope(|world, mut scene_spawner: Mut<SceneSpawner>| {
         // remove any loading instances where parent is deleted
-        let mut dead_instances = <HashSet<_>>::default();
-        scene_spawner
-            .scenes_with_parent
-            .retain(|(instance, parent)| {
-                let retain = world.get_entity(*parent).is_ok();
-
-                if !retain {
-                    dead_instances.insert(*instance);
-                }
-
-                retain
-            });
+        let is_parent_alive = |parent: &Option<Entity>| {
+            parent
+                .map(|parent| world.get_entity(parent).is_ok())
+                .unwrap_or(true) // If we don't have a parent, then consider the parent alive.
+        };
         scene_spawner
             .dynamic_scenes_to_spawn
-            .retain(|(_, instance, _)| !dead_instances.contains(instance));
+            .retain(|(_, _, parent)| is_parent_alive(parent));
         scene_spawner
             .scenes_to_spawn
-            .retain(|(_, instance, _)| !dead_instances.contains(instance));
+            .retain(|(_, _, parent)| is_parent_alive(parent));
 
-        let scene_asset_events = world.resource::<Events<AssetEvent<DynamicScene>>>();
+        let scene_asset_events = world.resource::<Events<AssetEvent<Scene>>>();
+        let dynamic_scene_asset_events = world.resource::<Events<AssetEvent<DynamicScene>>>();
+        let scene_spawner = &mut *scene_spawner;
 
         let mut updated_spawned_scenes = Vec::new();
-        let scene_spawner = &mut *scene_spawner;
         for event in scene_spawner
             .scene_asset_event_reader
             .read(scene_asset_events)
         {
             if let AssetEvent::Modified { id } = event {
-                if scene_spawner.spawned_dynamic_scenes.contains_key(id) {
+                if scene_spawner.spawned_scenes.contains_key(id) {
                     updated_spawned_scenes.push(*id);
                 }
             }
         }
+        let mut updated_spawned_dynamic_scenes = Vec::new();
+        for event in scene_spawner
+            .dynamic_scene_asset_event_reader
+            .read(dynamic_scene_asset_events)
+        {
+            if let AssetEvent::Modified { id } = event {
+                if scene_spawner.spawned_dynamic_scenes.contains_key(id) {
+                    updated_spawned_dynamic_scenes.push(*id);
+                }
+            }
+        }
 
         scene_spawner.despawn_queued_scenes(world).unwrap();
         scene_spawner.despawn_queued_instances(world);
@@ -494,7 +578,9 @@ pub fn scene_spawner_system(world: &mut World) {
         scene_spawner
             .update_spawned_scenes(world, &updated_spawned_scenes)
             .unwrap();
-        scene_spawner.set_scene_instance_parent_sync(world);
+        scene_spawner
+            .update_spawned_dynamic_scenes(world, &updated_spawned_dynamic_scenes)
+            .unwrap();
         scene_spawner.trigger_scene_ready_events(world);
     });
 }
@@ -615,7 +701,7 @@ mod tests {
 
         // let's try to delete the scene
         let mut scene_spawner = app.world_mut().resource_mut::<SceneSpawner>();
-        scene_spawner.despawn(&scene_handle);
+        scene_spawner.despawn_dynamic(&scene_handle);
 
         // run the scene spawner system to despawn the scene
         app.update();

release-content/migration-guides/scene_spawner_api.md

@@ -0,0 +1,12 @@
+---
+title: `SceneSpawner` methods have been renamed and replaced.
+pull_requests: [18358]
+---
+
+Some methods on `SceneSpawner` have been renamed:
+    - `despawn` -> `despawn_dynamic`
+    - `despawn_sync` -> `despawn_dynamic_sync`
+    - `update_spawned_scenes` -> `update_spawned_dynamic_scenes`
+
+In their place, we've added `despawn`, `despawn_sync`, and `update_spawned_scenes` which all act on
+`Scene`s (as opposed to `DynamicScene`s).