Relationships (non-fragmenting, one-to-many)

benches/Cargo.toml

@@ -16,7 +16,6 @@ criterion = { version = "0.5.1", features = ["html_reports"] }
 # Bevy crates
 bevy_app = { path = "../crates/bevy_app" }
 bevy_ecs = { path = "../crates/bevy_ecs", features = ["multi_threaded"] }
-bevy_hierarchy = { path = "../crates/bevy_hierarchy" }
 bevy_math = { path = "../crates/bevy_math" }
 bevy_picking = { path = "../crates/bevy_picking", features = [
   "bevy_mesh_picking_backend",

benches/benches/bevy_ecs/entity_cloning.rs

@@ -3,9 +3,9 @@ use core::hint::black_box;
 use benches::bench;
 use bevy_ecs::bundle::Bundle;
 use bevy_ecs::component::ComponentCloneHandler;
+use bevy_ecs::hierarchy::Parent;
 use bevy_ecs::reflect::AppTypeRegistry;
 use bevy_ecs::{component::Component, world::World};
-use bevy_hierarchy::{BuildChildren, CloneEntityHierarchyExt};
 use bevy_math::Mat4;
 use bevy_reflect::{GetTypeRegistration, Reflect};
 use criterion::{criterion_group, Bencher, Criterion, Throughput};
@@ -142,8 +142,7 @@ fn bench_clone_hierarchy<B: Bundle + Default + GetTypeRegistration>(
 
         for parent_id in current_hierarchy_level {
             for _ in 0..children {
-                let child_id = world.spawn(B::default()).set_parent(parent_id).id();
-
+                let child_id = world.spawn((B::default(), Parent(parent_id))).id();
                 hierarchy_level.push(child_id);
             }
         }

benches/benches/bevy_ecs/observers/propagation.rs

@@ -1,10 +1,6 @@
 use core::hint::black_box;
 
-use bevy_ecs::{
-    component::Component, entity::Entity, event::Event, observer::Trigger, world::World,
-};
-use bevy_hierarchy::{BuildChildren, Parent};
-
+use bevy_ecs::prelude::*;
 use criterion::Criterion;
 use rand::SeedableRng;
 use rand::{seq::IteratorRandom, Rng};

benches/benches/bevy_ecs/world/despawn_recursive.rs

@@ -1,7 +1,4 @@
 use bevy_ecs::prelude::*;
-use bevy_hierarchy::despawn_with_children_recursive;
-use bevy_hierarchy::BuildChildren;
-use bevy_hierarchy::ChildBuild;
 use criterion::Criterion;
 use glam::*;
 
@@ -29,7 +26,7 @@ pub fn world_despawn_recursive(criterion: &mut Criterion) {
         group.bench_function(format!("{}_entities", entity_count), |bencher| {
             bencher.iter(|| {
                 ents.iter().for_each(|e| {
-                    despawn_with_children_recursive(&mut world, *e, true);
+                    world.entity_mut(*e).despawn();
                 });
             });
         });

crates/bevy_animation/Cargo.toml

@@ -25,7 +25,6 @@ bevy_time = { path = "../bevy_time", version = "0.16.0-dev" }
 bevy_utils = { path = "../bevy_utils", version = "0.16.0-dev" }
 bevy_ecs = { path = "../bevy_ecs", version = "0.16.0-dev" }
 bevy_transform = { path = "../bevy_transform", version = "0.16.0-dev" }
-bevy_hierarchy = { path = "../bevy_hierarchy", version = "0.16.0-dev" }
 
 # other
 petgraph = { version = "0.6", features = ["serde-1"] }

crates/bevy_app/src/app.rs

@@ -104,6 +104,8 @@ impl Default for App {
         {
             app.init_resource::<AppTypeRegistry>();
             app.register_type::<Name>();
+            app.register_type::<Parent>();
+            app.register_type::<Children>();
         }
 
         #[cfg(feature = "reflect_functions")]

crates/bevy_audio/Cargo.toml

@@ -13,7 +13,6 @@ keywords = ["bevy"]
 bevy_app = { path = "../bevy_app", version = "0.16.0-dev" }
 bevy_asset = { path = "../bevy_asset", version = "0.16.0-dev" }
 bevy_ecs = { path = "../bevy_ecs", version = "0.16.0-dev" }
-bevy_hierarchy = { path = "../bevy_hierarchy", version = "0.16.0-dev" }
 bevy_math = { path = "../bevy_math", version = "0.16.0-dev" }
 bevy_reflect = { path = "../bevy_reflect", version = "0.16.0-dev", features = [
   "bevy",

crates/bevy_audio/src/audio_output.rs

@@ -4,7 +4,6 @@ use crate::{
 };
 use bevy_asset::{Asset, Assets};
 use bevy_ecs::{prelude::*, system::SystemParam};
-use bevy_hierarchy::DespawnRecursiveExt;
 use bevy_math::Vec3;
 use bevy_transform::prelude::GlobalTransform;
 use rodio::{OutputStream, OutputStreamHandle, Sink, Source, SpatialSink};
@@ -253,12 +252,12 @@ pub(crate) fn cleanup_finished_audio<T: Decodable + Asset>(
 ) {
     for (entity, sink) in &query_nonspatial_despawn {
         if sink.sink.empty() {
-            commands.entity(entity).despawn_recursive();
+            commands.entity(entity).despawn();
         }
     }
     for (entity, sink) in &query_spatial_despawn {
         if sink.sink.empty() {
-            commands.entity(entity).despawn_recursive();
+            commands.entity(entity).despawn();
         }
     }
     for (entity, sink) in &query_nonspatial_remove {

crates/bevy_dev_tools/Cargo.toml

@@ -18,7 +18,6 @@ bevy_asset = { path = "../bevy_asset", version = "0.16.0-dev" }
 bevy_color = { path = "../bevy_color", version = "0.16.0-dev" }
 bevy_diagnostic = { path = "../bevy_diagnostic", version = "0.16.0-dev" }
 bevy_ecs = { path = "../bevy_ecs", version = "0.16.0-dev" }
-bevy_hierarchy = { path = "../bevy_hierarchy", version = "0.16.0-dev" }
 bevy_input = { path = "../bevy_input", version = "0.16.0-dev" }
 bevy_picking = { path = "../bevy_picking", version = "0.16.0-dev" }
 bevy_render = { path = "../bevy_render", version = "0.16.0-dev" }

crates/bevy_dev_tools/src/fps_overlay.rs

@@ -12,7 +12,6 @@ use bevy_ecs::{
     schedule::{common_conditions::resource_changed, IntoSystemConfigs},
     system::{Commands, Query, Res, Resource},
 };
-use bevy_hierarchy::{BuildChildren, ChildBuild};
 use bevy_render::view::Visibility;
 use bevy_text::{Font, TextColor, TextFont, TextSpan};
 use bevy_ui::{