Preserve spawned RelationshipTarget order and other improvements

benches/benches/bevy_ecs/entity_cloning.rs

@@ -55,7 +55,7 @@ type ComplexBundle = (C1, C2, C3, C4, C5, C6, C7, C8, C9, C10);
 /// use the [`Reflect`] trait instead of [`Clone`].
 fn reflection_cloner<B: Bundle + GetTypeRegistration>(
     world: &mut World,
-    recursive: bool,
+    linked_cloning: bool,
 ) -> EntityCloner {
     // Get mutable access to the type registry, creating it if it does not exist yet.
     let registry = world.get_resource_or_init::<AppTypeRegistry>();
@@ -77,7 +77,7 @@ fn reflection_cloner<B: Bundle + GetTypeRegistration>(
     for component in component_ids {
         builder.override_clone_behavior_with_id(component, ComponentCloneBehavior::reflect());
     }
-    builder.recursive(recursive);
+    builder.linked_cloning(linked_cloning);
 
     builder.finish()
 }
@@ -136,7 +136,7 @@ fn bench_clone_hierarchy<B: Bundle + Default + GetTypeRegistration>(
         reflection_cloner::<B>(&mut world, true)
     } else {
         let mut builder = EntityCloner::build(&mut world);
-        builder.recursive(true);
+        builder.linked_cloning(true);
         builder.finish()
     };
 

crates/bevy_ecs/macros/src/component.rs

@@ -71,7 +71,12 @@ pub fn derive_component(input: TokenStream) -> TokenStream {
         Err(err) => err.into_compile_error().into(),
     };
 
-    let visit_entities = visit_entities(&ast.data, &bevy_ecs_path, relationship.is_some());
+    let visit_entities = visit_entities(
+        &ast.data,
+        &bevy_ecs_path,
+        relationship.is_some(),
+        relationship_target.is_some(),
+    );
 
     let storage = storage_path(&bevy_ecs_path, attrs.storage);
 
@@ -207,7 +212,7 @@ pub fn derive_component(input: TokenStream) -> TokenStream {
         .unwrap_or(quote! { #bevy_ecs_path::component::Mutable });
 
     let clone_behavior = if relationship_target.is_some() {
-        quote!(#bevy_ecs_path::component::ComponentCloneBehavior::RelationshipTarget(#bevy_ecs_path::relationship::clone_relationship_target::<Self>))
+        quote!(#bevy_ecs_path::component::ComponentCloneBehavior::Custom(#bevy_ecs_path::relationship::clone_relationship_target::<Self>))
     } else {
         quote!(
             use #bevy_ecs_path::component::{DefaultCloneBehaviorBase, DefaultCloneBehaviorViaClone};
@@ -255,7 +260,12 @@ pub fn derive_component(input: TokenStream) -> TokenStream {
     })
 }
 
-fn visit_entities(data: &Data, bevy_ecs_path: &Path, is_relationship: bool) -> TokenStream2 {
+fn visit_entities(
+    data: &Data,
+    bevy_ecs_path: &Path,
+    is_relationship: bool,
+    is_relationship_target: bool,
+) -> TokenStream2 {
     match data {
         Data::Struct(DataStruct { fields, .. }) => {
             let mut visited_fields = Vec::new();
@@ -288,7 +298,9 @@ fn visit_entities(data: &Data, bevy_ecs_path: &Path, is_relationship: bool) -> T
                 }
                 Fields::Unnamed(fields) => {
                     for (index, field) in fields.unnamed.iter().enumerate() {
-                        if field
+                        if index == 0 && is_relationship_target {
+                            visited_indices.push(Index::from(0));
+                        } else if field
                             .attrs
                             .iter()
                             .any(|a| a.meta.path().is_ident(ENTITIES_ATTR))

crates/bevy_ecs/src/bundle.rs

@@ -18,6 +18,7 @@ use crate::{
     observer::Observers,
     prelude::World,
     query::DebugCheckedUnwrap,
+    relationship::RelationshipInsertHookMode,
     storage::{SparseSetIndex, SparseSets, Storages, Table, TableRow},
     world::{unsafe_world_cell::UnsafeWorldCell, EntityWorldMut, ON_ADD, ON_INSERT, ON_REPLACE},
 };
@@ -1100,6 +1101,7 @@ impl<'w> BundleInserter<'w> {
         bundle: T,
         insert_mode: InsertMode,
         caller: MaybeLocation,
+        relationship_insert_hook_mode: RelationshipInsertHookMode,
     ) -> (EntityLocation, T::Effect) {
         let bundle_info = self.bundle_info.as_ref();
         let archetype_after_insert = self.archetype_after_insert.as_ref();
@@ -1312,6 +1314,7 @@ impl<'w> BundleInserter<'w> {
                         entity,
                         archetype_after_insert.iter_inserted(),
                         caller,
+                        relationship_insert_hook_mode,
                     );
                     if new_archetype.has_insert_observer() {
                         deferred_world.trigger_observers(
@@ -1330,6 +1333,7 @@ impl<'w> BundleInserter<'w> {
                         entity,
                         archetype_after_insert.iter_added(),
                         caller,
+                        relationship_insert_hook_mode,
                     );
                     if new_archetype.has_insert_observer() {
                         deferred_world.trigger_observers(
@@ -1474,6 +1478,7 @@ impl<'w> BundleSpawner<'w> {
                 entity,
                 bundle_info.iter_contributed_components(),
                 caller,
+                RelationshipInsertHookMode::Run,
             );
             if archetype.has_insert_observer() {
                 deferred_world.trigger_observers(

crates/bevy_ecs/src/component.rs

@@ -4,8 +4,9 @@ use crate::{
     archetype::ArchetypeFlags,
     bundle::BundleInfo,
     change_detection::{MaybeLocation, MAX_CHANGE_AGE},
-    entity::{ComponentCloneCtx, Entity},
+    entity::{ComponentCloneCtx, Entity, SourceComponent},
     query::DebugCheckedUnwrap,
+    relationship::RelationshipInsertHookMode,
     resource::Resource,
     storage::{SparseSetIndex, SparseSets, Table, TableRow},
     system::{Commands, Local, SystemParam},
@@ -544,6 +545,8 @@ pub struct HookContext {
     pub component_id: ComponentId,
     /// The caller location is `Some` if the `track_caller` feature is enabled.
     pub caller: MaybeLocation,
+    /// Configures how relationship hooks will run
+    pub relationship_insert_hook_mode: RelationshipInsertHookMode,
 }
 
 /// [`World`]-mutating functions that run as part of lifecycle events of a [`Component`].
@@ -1085,7 +1088,7 @@ impl ComponentDescriptor {
 }
 
 /// Function type that can be used to clone an entity.
-pub type ComponentCloneFn = fn(&mut Commands, &mut ComponentCloneCtx);
+pub type ComponentCloneFn = fn(&mut Commands, &SourceComponent, &mut ComponentCloneCtx);
 
 /// The clone behavior to use when cloning a [`Component`].
 #[derive(Clone, Debug, Default, PartialEq, Eq)]
@@ -1097,11 +1100,6 @@ pub enum ComponentCloneBehavior {
     Ignore,
     /// Uses a custom [`ComponentCloneFn`].
     Custom(ComponentCloneFn),
-    /// Uses a [`ComponentCloneFn`] that produces an empty version of the given relationship target.
-    // TODO: this exists so that the current scene spawning code can know when to skip these components.
-    // When we move to actually cloning entities in scene spawning code, this should be removed in favor of Custom, as the
-    // distinction will no longer be necessary.
-    RelationshipTarget(ComponentCloneFn),
 }
 
 impl ComponentCloneBehavior {
@@ -1132,8 +1130,7 @@ impl ComponentCloneBehavior {
         match self {
             ComponentCloneBehavior::Default => default,
             ComponentCloneBehavior::Ignore => component_clone_ignore,
-            ComponentCloneBehavior::Custom(custom)
-            | ComponentCloneBehavior::RelationshipTarget(custom) => *custom,
+            ComponentCloneBehavior::Custom(custom) => *custom,
         }
     }
 }
@@ -2166,9 +2163,10 @@ pub fn enforce_no_required_components_recursion(
 ///
 pub fn component_clone_via_clone<C: Clone + Component>(
     _commands: &mut Commands,
+    source: &SourceComponent,
     ctx: &mut ComponentCloneCtx,
 ) {
-    if let Some(component) = ctx.read_source_component::<C>() {
+    if let Some(component) = source.read::<C>() {
         ctx.write_target_component(component.clone());
     }
 }
@@ -2189,17 +2187,21 @@ pub fn component_clone_via_clone<C: Clone + Component>(
 ///
 /// See [`EntityClonerBuilder`](crate::entity::EntityClonerBuilder) for details.
 #[cfg(feature = "bevy_reflect")]
-pub fn component_clone_via_reflect(commands: &mut Commands, ctx: &mut ComponentCloneCtx) {
+pub fn component_clone_via_reflect(
+    commands: &mut Commands,
+    source: &SourceComponent,
+    ctx: &mut ComponentCloneCtx,
+) {
     let Some(app_registry) = ctx.type_registry().cloned() else {
         return;
     };
-    let Some(source_component_reflect) = ctx.read_source_component_reflect() else {
+    let registry = app_registry.read();
+    let Some(source_component_reflect) = source.read_reflect(&registry) else {
         return;
     };
     let component_info = ctx.component_info();
     // checked in read_source_component_reflect
     let type_id = component_info.type_id().unwrap();
-    let registry = app_registry.read();
 
     // Try to clone using ReflectFromReflect
     if let Some(reflect_from_reflect) =
@@ -2284,7 +2286,12 @@ pub fn component_clone_via_reflect(commands: &mut Commands, ctx: &mut ComponentC
 /// Noop implementation of component clone handler function.
 ///
 /// See [`EntityClonerBuilder`](crate::entity::EntityClonerBuilder) for details.
-pub fn component_clone_ignore(_commands: &mut Commands, _ctx: &mut ComponentCloneCtx) {}
+pub fn component_clone_ignore(
+    _commands: &mut Commands,
+    _source: &SourceComponent,
+    _ctx: &mut ComponentCloneCtx,
+) {
+}
 
 /// Wrapper for components clone specialization using autoderef.
 #[doc(hidden)]