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_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::{

crates/bevy_ecs/macros/src/component.rs

@@ -64,7 +64,9 @@ pub fn derive_component(input: TokenStream) -> TokenStream {
     let on_add = hook_register_function_call(quote! {on_add}, attrs.on_add);
     let on_insert = hook_register_function_call(quote! {on_insert}, attrs.on_insert);
     let on_replace = hook_register_function_call(quote! {on_replace}, attrs.on_replace);
-    let on_remove = hook_register_function_call(quote! {on_remove}, attrs.on_remove);
+    let on_remove: Option<TokenStream2> =
+        hook_register_function_call(quote! {on_remove}, attrs.on_remove);
+    let on_despawn = hook_register_function_call(quote! {on_despawn}, attrs.on_despawn);
 
     ast.generics
         .make_where_clause()
@@ -160,6 +162,7 @@ pub fn derive_component(input: TokenStream) -> TokenStream {
                 #on_insert
                 #on_replace
                 #on_remove
+                #on_despawn
             }
 
             fn get_component_clone_handler() -> #bevy_ecs_path::component::ComponentCloneHandler {
@@ -207,6 +210,7 @@ pub const ON_ADD: &str = "on_add";
 pub const ON_INSERT: &str = "on_insert";
 pub const ON_REPLACE: &str = "on_replace";
 pub const ON_REMOVE: &str = "on_remove";
+pub const ON_DESPAWN: &str = "on_despawn";
 
 pub const IMMUTABLE: &str = "immutable";
 
@@ -217,6 +221,7 @@ struct Attrs {
     on_insert: Option<ExprPath>,
     on_replace: Option<ExprPath>,
     on_remove: Option<ExprPath>,
+    on_despawn: Option<ExprPath>,
     immutable: bool,
 }
 
@@ -247,6 +252,7 @@ fn parse_component_attr(ast: &DeriveInput) -> Result<Attrs> {
         on_insert: None,
         on_replace: None,
         on_remove: None,
+        on_despawn: None,
         requires: None,
         immutable: false,
     };
@@ -278,6 +284,9 @@ fn parse_component_attr(ast: &DeriveInput) -> Result<Attrs> {
                 } else if nested.path.is_ident(ON_REMOVE) {
                     attrs.on_remove = Some(nested.value()?.parse::<ExprPath>()?);
                     Ok(())
+                } else if nested.path.is_ident(ON_DESPAWN) {
+                    attrs.on_despawn = Some(nested.value()?.parse::<ExprPath>()?);
+                    Ok(())
                 } else if nested.path.is_ident(IMMUTABLE) {
                     attrs.immutable = true;
                     Ok(())

crates/bevy_ecs/macros/src/lib.rs

@@ -6,6 +6,7 @@ extern crate proc_macro;
 mod component;
 mod query_data;
 mod query_filter;
+mod relationship;
 mod states;
 mod world_query;
 
@@ -611,3 +612,13 @@ pub fn derive_states(input: TokenStream) -> TokenStream {
 pub fn derive_substates(input: TokenStream) -> TokenStream {
     states::derive_substates(input)
 }
+
+#[proc_macro_derive(Relationship, attributes(relationship))]
+pub fn derive_relationship(input: TokenStream) -> TokenStream {
+    relationship::derive_relationship(input)
+}
+
+#[proc_macro_derive(RelationshipSources, attributes(relationship_sources))]
+pub fn derive_relationship_sources(input: TokenStream) -> TokenStream {
+    relationship::derive_relationship_sources(input)
+}