Implement and require #[derive(Component)] on all component structs (#2254)

This implements the most minimal variant of #1843 - a derive for marker trait. This is a prerequisite to more complicated features like statically defined storage type or opt-out component reflection.

In order to make component struct's purpose explicit and avoid misuse, it must be annotated with `#[derive(Component)]` (manual impl is discouraged for compatibility). Right now this is just a marker trait, but in the future it might be expanded. Making this change early allows us to make further changes later without breaking backward compatibility for derive macro users.

This already prevents a lot of issues, like using bundles in `insert` calls. Primitive types are no longer valid components as well. This can be easily worked around by adding newtype wrappers and deriving `Component` for them.

One funny example of prevented bad code (from our own tests) is when an newtype struct or enum variant is used. Previously, it was possible to write `insert(Newtype)` instead of `insert(Newtype(value))`. That code compiled, because function pointers (in this case newtype struct constructor) implement `Send + Sync + 'static`, so we allowed them to be used as components. This is no longer the case and such invalid code will trigger a compile error.


Co-authored-by: = <=>
Co-authored-by: TheRawMeatball <[email protected]>
Co-authored-by: Carter Anderson <[email protected]>

Author: 3 people

Cargo.toml

@@ -46,7 +46,7 @@ bevy_audio = ["bevy_internal/bevy_audio"]
 bevy_dynamic_plugin = ["bevy_internal/bevy_dynamic_plugin"]
 bevy_gilrs = ["bevy_internal/bevy_gilrs"]
 bevy_gltf = ["bevy_internal/bevy_gltf"]
-bevy_wgpu = ["bevy_internal/bevy_wgpu"]
+bevy_wgpu = ["bevy_internal/bevy_wgpu"] 
 bevy_winit = ["bevy_internal/bevy_winit"]
 
 trace_chrome = ["bevy_internal/trace_chrome"]

benches/benches/bevy_ecs/commands.rs

@@ -1,4 +1,5 @@
 use bevy::ecs::{
+    component::Component,
     entity::Entity,
     system::{Command, CommandQueue, Commands},
     world::World,
@@ -18,8 +19,11 @@ criterion_group!(
 );
 criterion_main!(benches);
 
+#[derive(Component)]
 struct A;
+#[derive(Component)]
 struct B;
+#[derive(Component)]
 struct C;
 
 fn empty_commands(criterion: &mut Criterion) {
@@ -79,10 +83,10 @@ fn spawn_commands(criterion: &mut Criterion) {
     group.finish();
 }
 
-#[derive(Default)]
+#[derive(Default, Component)]
 struct Matrix([[f32; 4]; 4]);
 
-#[derive(Default)]
+#[derive(Default, Component)]
 struct Vec3([f32; 3]);
 
 fn insert_commands(criterion: &mut Criterion) {
@@ -95,14 +99,16 @@ fn insert_commands(criterion: &mut Criterion) {
         let mut world = World::default();
         let mut command_queue = CommandQueue::default();
         let mut entities = Vec::new();
-        for i in 0..entity_count {
+        for _ in 0..entity_count {
             entities.push(world.spawn().id());
         }
 
         bencher.iter(|| {
             let mut commands = Commands::new(&mut command_queue, &world);
             for entity in entities.iter() {
-                commands.entity(*entity).insert_bundle((Matrix::default(), Vec3::default()));
+                commands
+                    .entity(*entity)
+                    .insert_bundle((Matrix::default(), Vec3::default()));
             }
             drop(commands);
             command_queue.apply(&mut world);
@@ -112,7 +118,7 @@ fn insert_commands(criterion: &mut Criterion) {
         let mut world = World::default();
         let mut command_queue = CommandQueue::default();
         let mut entities = Vec::new();
-        for i in 0..entity_count {
+        for _ in 0..entity_count {
             entities.push(world.spawn().id());
         }
 

benches/benches/bevy_ecs/stages.rs

@@ -1,6 +1,7 @@
 use bevy::ecs::{
+    component::Component,
     schedule::{Stage, SystemStage},
-    system::{IntoSystem, Query},
+    system::Query,
     world::World,
 };
 use criterion::{criterion_group, criterion_main, Criterion};
@@ -12,10 +13,15 @@ fn run_stage(stage: &mut SystemStage, world: &mut World) {
     stage.run(world);
 }
 
+#[derive(Component)]
 struct A(f32);
+#[derive(Component)]
 struct B(f32);
+#[derive(Component)]
 struct C(f32);
+#[derive(Component)]
 struct D(f32);
+#[derive(Component)]
 struct E(f32);
 
 const ENTITY_BUNCH: usize = 5000;

benches/benches/bevy_ecs/world_get.rs

@@ -1,8 +1,4 @@
-use bevy::ecs::{
-    component::{ComponentDescriptor, StorageType},
-    entity::Entity,
-    world::World,
-};
+use bevy::ecs::{component::Component, entity::Entity, world::World};
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
 
 criterion_group!(
@@ -15,16 +11,18 @@ criterion_group!(
 );
 criterion_main!(benches);
 
-struct A(f32);
+#[derive(Component, Default)]
+#[component(storage = "Table")]
+struct Table(f32);
+#[derive(Component, Default)]
+#[component(storage = "SparseSet")]
+struct Sparse(f32);
 
 const RANGE: std::ops::Range<u32> = 5..6;
 
-fn setup(entity_count: u32, storage: StorageType) -> World {
+fn setup<T: Component + Default>(entity_count: u32) -> World {
     let mut world = World::default();
-    world
-        .register_component(ComponentDescriptor::new::<A>(storage))
-        .unwrap();
-    world.spawn_batch((0..entity_count).map(|_| (A(0.0),)));
+    world.spawn_batch((0..entity_count).map(|_| (T::default(),)));
     world
 }
 
@@ -35,7 +33,7 @@ fn world_entity(criterion: &mut Criterion) {
 
     for entity_count in RANGE.map(|i| i * 10_000) {
         group.bench_function(format!("{}_entities", entity_count), |bencher| {
-            let world = setup(entity_count, StorageType::Table);
+            let world = setup::<Table>(entity_count);
 
             bencher.iter(|| {
                 for i in 0..entity_count {
@@ -55,21 +53,26 @@ fn world_get(criterion: &mut Criterion) {
     group.measurement_time(std::time::Duration::from_secs(4));
 
     for entity_count in RANGE.map(|i| i * 10_000) {
-        for storage in [StorageType::Table, StorageType::SparseSet] {
-            group.bench_function(
-                format!("{}_entities_{:?}", entity_count, storage),
-                |bencher| {
-                    let world = setup(entity_count, storage);
-
-                    bencher.iter(|| {
-                        for i in 0..entity_count {
-                            let entity = Entity::new(i);
-                            assert!(world.get::<A>(entity).is_some());
-                        }
-                    });
-                },
-            );
-        }
+        group.bench_function(format!("{}_entities_table", entity_count), |bencher| {
+            let world = setup::<Table>(entity_count);
+
+            bencher.iter(|| {
+                for i in 0..entity_count {
+                    let entity = Entity::new(i);
+                    assert!(world.get::<Table>(entity).is_some());
+                }
+            });
+        });
+        group.bench_function(format!("{}_entities_sparse", entity_count), |bencher| {
+            let world = setup::<Sparse>(entity_count);
+
+            bencher.iter(|| {
+                for i in 0..entity_count {
+                    let entity = Entity::new(i);
+                    assert!(world.get::<Sparse>(entity).is_some());
+                }
+            });
+        });
     }
 
     group.finish();
@@ -81,22 +84,28 @@ fn world_query_get(criterion: &mut Criterion) {
     group.measurement_time(std::time::Duration::from_secs(4));
 
     for entity_count in RANGE.map(|i| i * 10_000) {
-        for storage in [StorageType::Table, StorageType::SparseSet] {
-            group.bench_function(
-                format!("{}_entities_{:?}", entity_count, storage),
-                |bencher| {
-                    let mut world = setup(entity_count, storage);
-                    let mut query = world.query::<&A>();
-
-                    bencher.iter(|| {
-                        for i in 0..entity_count {
-                            let entity = Entity::new(i);
-                            assert!(query.get(&world, entity).is_ok());
-                        }
-                    });
-                },
-            );
-        }
+        group.bench_function(format!("{}_entities_table", entity_count), |bencher| {
+            let mut world = setup::<Table>(entity_count);
+            let mut query = world.query::<&Table>();
+
+            bencher.iter(|| {
+                for i in 0..entity_count {
+                    let entity = Entity::new(i);
+                    assert!(query.get(&world, entity).is_ok());
+                }
+            });
+        });
+        group.bench_function(format!("{}_entities_sparse", entity_count), |bencher| {
+            let mut world = setup::<Sparse>(entity_count);
+            let mut query = world.query::<&Sparse>();
+
+            bencher.iter(|| {
+                for i in 0..entity_count {
+                    let entity = Entity::new(i);
+                    assert!(query.get(&world, entity).is_ok());
+                }
+            });
+        });
     }
 
     group.finish();
@@ -108,24 +117,32 @@ fn world_query_iter(criterion: &mut Criterion) {
     group.measurement_time(std::time::Duration::from_secs(4));
 
     for entity_count in RANGE.map(|i| i * 10_000) {
-        for storage in [StorageType::Table, StorageType::SparseSet] {
-            group.bench_function(
-                format!("{}_entities_{:?}", entity_count, storage),
-                |bencher| {
-                    let mut world = setup(entity_count, storage);
-                    let mut query = world.query::<&A>();
-
-                    bencher.iter(|| {
-                        let mut count = 0;
-                        for comp in query.iter(&world) {
-                            black_box(comp);
-                            count += 1;
-                        }
-                        assert_eq!(black_box(count), entity_count);
-                    });
-                },
-            );
-        }
+        group.bench_function(format!("{}_entities_table", entity_count), |bencher| {
+            let mut world = setup::<Table>(entity_count);
+            let mut query = world.query::<&Table>();
+
+            bencher.iter(|| {
+                let mut count = 0;
+                for comp in query.iter(&world) {
+                    black_box(comp);
+                    count += 1;
+                }
+                assert_eq!(black_box(count), entity_count);
+            });
+        });
+        group.bench_function(format!("{}_entities_sparse", entity_count), |bencher| {
+            let mut world = setup::<Sparse>(entity_count);
+            let mut query = world.query::<&Sparse>();
+
+            bencher.iter(|| {
+                let mut count = 0;
+                for comp in query.iter(&world) {
+                    black_box(comp);
+                    count += 1;
+                }
+                assert_eq!(black_box(count), entity_count);
+            });
+        });
     }
 
     group.finish();
@@ -137,24 +154,32 @@ fn world_query_for_each(criterion: &mut Criterion) {
     group.measurement_time(std::time::Duration::from_secs(4));
 
     for entity_count in RANGE.map(|i| i * 10_000) {
-        for storage in [StorageType::Table, StorageType::SparseSet] {
-            group.bench_function(
-                format!("{}_entities_{:?}", entity_count, storage),
-                |bencher| {
-                    let mut world = setup(entity_count, storage);
-                    let mut query = world.query::<&A>();
-
-                    bencher.iter(|| {
-                        let mut count = 0;
-                        query.for_each(&world, |comp| {
-                            black_box(comp);
-                            count += 1;
-                        });
-                        assert_eq!(black_box(count), entity_count);
-                    });
-                },
-            );
-        }
+        group.bench_function(format!("{}_entities_table", entity_count), |bencher| {
+            let mut world = setup::<Table>(entity_count);
+            let mut query = world.query::<&Table>();
+
+            bencher.iter(|| {
+                let mut count = 0;
+                query.for_each(&world, |comp| {
+                    black_box(comp);
+                    count += 1;
+                });
+                assert_eq!(black_box(count), entity_count);
+            });
+        });
+        group.bench_function(format!("{}_entities_sparse", entity_count), |bencher| {
+            let mut world = setup::<Sparse>(entity_count);
+            let mut query = world.query::<&Sparse>();
+
+            bencher.iter(|| {
+                let mut count = 0;
+                query.for_each(&world, |comp| {
+                    black_box(comp);
+                    count += 1;
+                });
+                assert_eq!(black_box(count), entity_count);
+            });
+        });
     }
 
     group.finish();

crates/bevy_app/src/app.rs

@@ -1,14 +1,15 @@
 use crate::{CoreStage, Events, Plugin, PluginGroup, PluginGroupBuilder, StartupStage};
 use bevy_ecs::{
-    component::{Component, ComponentDescriptor},
     prelude::{FromWorld, IntoExclusiveSystem},
     schedule::{
-        IntoSystemDescriptor, RunOnce, Schedule, Stage, StageLabel, State, SystemSet, SystemStage,
+        IntoSystemDescriptor, RunOnce, Schedule, Stage, StageLabel, State, StateData, SystemSet,
+        SystemStage,
     },
+    system::Resource,
     world::World,
 };
 use bevy_utils::tracing::debug;
-use std::{fmt::Debug, hash::Hash};
+use std::fmt::Debug;
 
 #[cfg(feature = "trace")]
 use bevy_utils::tracing::info_span;
@@ -493,7 +494,7 @@ impl App {
     /// adding [State::get_driver] to additional stages you need it in.
     pub fn add_state<T>(&mut self, initial: T) -> &mut Self
     where
-        T: Component + Debug + Clone + Eq + Hash,
+        T: StateData,
     {
         self.add_state_to_stage(CoreStage::Update, initial)
     }
@@ -505,7 +506,7 @@ impl App {
     /// stages you need it in.
     pub fn add_state_to_stage<T>(&mut self, stage: impl StageLabel, initial: T) -> &mut Self
     where
-        T: Component + Debug + Clone + Eq + Hash,
+        T: StateData,
     {
         self.insert_resource(State::new(initial))
             .add_system_set_to_stage(stage, State::<T>::get_driver())
@@ -582,7 +583,7 @@ impl App {
     /// ```
     pub fn add_event<T>(&mut self) -> &mut Self
     where
-        T: Component,
+        T: Resource,
     {
         self.init_resource::<Events<T>>()
             .add_system_to_stage(CoreStage::First, Events::<T>::update_system)
@@ -608,7 +609,7 @@ impl App {
     /// ```
     pub fn insert_resource<T>(&mut self, resource: T) -> &mut Self
     where
-        T: Component,
+        T: Resource,
     {
         self.world.insert_resource(resource);
         self
@@ -810,18 +811,6 @@ impl App {
         self
     }
 
-    /// Registers a new component using the given [ComponentDescriptor].
-    ///
-    /// Components do not need to be manually registered. This just provides a way to
-    /// override default configuration. Attempting to register a component with a type
-    /// that has already been used by [World] will result in an error.
-    ///
-    /// See [World::register_component]
-    pub fn register_component(&mut self, descriptor: ComponentDescriptor) -> &mut Self {
-        self.world.register_component(descriptor).unwrap();
-        self
-    }
-
     /// Adds the type `T` to the type registry resource.
     #[cfg(feature = "bevy_reflect")]
     pub fn register_type<T: bevy_reflect::GetTypeRegistration>(&mut self) -> &mut Self {