Automatic registration of ECS types

crates/bevy_ecs/Cargo.toml

@@ -13,6 +13,7 @@ categories = ["game-engines", "data-structures"]
 trace = []
 multi-threaded = ["bevy_tasks/multi-threaded"]
 bevy_debug_stepping = []
+bevy_reflect = ["dep:bevy_reflect", "bevy_ecs_macros/bevy_reflect"]
 default = ["bevy_reflect", "bevy_debug_stepping"]
 
 [dependencies]

crates/bevy_ecs/macros/Cargo.toml

@@ -8,6 +8,9 @@ license = "MIT OR Apache-2.0"
 [lib]
 proc-macro = true
 
+[features]
+bevy_reflect = []
+
 [dependencies]
 bevy_macro_utils = { path = "../../bevy_macro_utils", version = "0.14.0-dev" }
 

crates/bevy_ecs/macros/src/component.rs

@@ -58,11 +58,35 @@ pub fn derive_component(input: TokenStream) -> TokenStream {
     let struct_name = &ast.ident;
     let (impl_generics, type_generics, where_clause) = &ast.generics.split_for_impl();
 
-    TokenStream::from(quote! {
-        impl #impl_generics #bevy_ecs_path::component::Component for #struct_name #type_generics #where_clause {
-            const STORAGE_TYPE: #bevy_ecs_path::component::StorageType = #storage;
+    #[cfg(not(feature = "bevy_reflect"))]
+    {
+        TokenStream::from(quote! {
+            impl #impl_generics #bevy_ecs_path::component::Component for #struct_name #type_generics #where_clause {
+                const STORAGE_TYPE: #bevy_ecs_path::component::StorageType = #storage;
+            }
+        })
+    }
+    #[cfg(feature = "bevy_reflect")]
+    {
+        if has_reflect_attr(&ast) {
+            TokenStream::from(quote! {
+                impl #impl_generics #bevy_ecs_path::component::Component for #struct_name #type_generics #where_clause {
+                    const STORAGE_TYPE: #bevy_ecs_path::component::StorageType = #storage;
+
+                    #[doc(hidden)]
+                    fn __register_type(registry: &#bevy_ecs_path::private::bevy_reflect::TypeRegistryArc) {
+                        registry.write().register::<Self>();
+                    }
+                }
+            })
+        } else {
+            TokenStream::from(quote! {
+                impl #impl_generics #bevy_ecs_path::component::Component for #struct_name #type_generics #where_clause {
+                    const STORAGE_TYPE: #bevy_ecs_path::component::StorageType = #storage;
+                }
+            })
         }
-    })
+    }
 }
 
 pub const COMPONENT: &str = "component";
@@ -109,6 +133,12 @@ fn parse_component_attr(ast: &DeriveInput) -> Result<Attrs> {
     Ok(attrs)
 }
 
+#[cfg(feature = "bevy_reflect")]
+fn has_reflect_attr(ast: &DeriveInput) -> bool {
+    const REFLECT: &str = "reflect";
+    ast.attrs.iter().any(|a| a.path().is_ident(REFLECT))
+}
+
 fn storage_path(bevy_ecs_path: &Path, ty: StorageTy) -> TokenStream2 {
     let storage_type = match ty {
         StorageTy::Table => Ident::new("Table", Span::call_site()),

crates/bevy_ecs/src/component.rs

@@ -12,7 +12,7 @@ use crate::{
 pub use bevy_ecs_macros::Component;
 use bevy_ptr::{OwningPtr, UnsafeCellDeref};
 #[cfg(feature = "bevy_reflect")]
-use bevy_reflect::Reflect;
+use bevy_reflect::{Reflect, TypeRegistryArc};
 use bevy_utils::TypeIdMap;
 use std::cell::UnsafeCell;
 use std::{
@@ -156,6 +156,13 @@ pub trait Component: Send + Sync + 'static {
 
     /// Called when registering this component, allowing mutable access to it's [`ComponentHooks`].
     fn register_component_hooks(_hooks: &mut ComponentHooks) {}
+
+    /// Shim for automatically registering components. Intentionally hidden as it's not part of the
+    /// public interface. Only available if the `bevy_reflect` feature is enabled.
+    #[doc(hidden)]
+    #[allow(unused_variables)]
+    #[cfg(feature = "bevy_reflect")]
+    fn __register_type(registry: &TypeRegistryArc) {}
 }
 
 /// The storage used for a specific component type.
@@ -525,6 +532,8 @@ pub struct Components {
     components: Vec<ComponentInfo>,
     indices: TypeIdMap<ComponentId>,
     resource_indices: TypeIdMap<ComponentId>,
+    #[cfg(feature = "bevy_reflect")]
+    pub(crate) type_registry: TypeRegistryArc,
 }
 
 impl Components {
@@ -552,6 +561,8 @@ impl Components {
                 ComponentDescriptor::new::<T>(),
             );
             T::register_component_hooks(&mut components[index.index()].hooks);
+            #[cfg(feature = "bevy_reflect")]
+            T::__register_type(&self.type_registry);
             index
         })
     }
@@ -971,3 +982,27 @@ impl<T: Component> FromWorld for InitComponentId<T> {
         }
     }
 }
+
+#[cfg(test)]
+mod test {
+    #[test]
+    #[cfg(feature = "bevy_reflect")]
+    fn init_component_registers_component() {
+        use crate as bevy_ecs;
+        use crate::{
+            component::Components, prelude::Component, reflect::ReflectComponent, storage::Storages,
+        };
+        use bevy_reflect::Reflect;
+        use core::any::TypeId;
+
+        #[derive(Component, Reflect)]
+        #[reflect(Component)]
+        struct A(usize);
+
+        let mut components = Components::default();
+        let mut storages = Storages::default();
+        components.init_component::<A>(&mut storages);
+
+        assert!(components.type_registry.read().contains(TypeId::of::<A>()));
+    }
+}

crates/bevy_ecs/src/lib.rs

@@ -52,6 +52,14 @@ pub mod prelude {
     };
 }
 
+#[cfg(feature = "bevy_reflect")]
+#[doc(hidden)]
+pub mod private {
+    pub mod bevy_reflect {
+        pub use bevy_reflect::*;
+    }
+}
+
 pub use bevy_utils::all_tuples;
 
 #[cfg(test)]

crates/bevy_ecs/src/reflect/mod.rs

@@ -4,7 +4,10 @@ use std::any::TypeId;
 use std::ops::{Deref, DerefMut};
 
 use crate as bevy_ecs;
-use crate::{system::Resource, world::World};
+use crate::{
+    system::Resource,
+    world::{FromWorld, World},
+};
 use bevy_reflect::{FromReflect, Reflect, TypeRegistry, TypeRegistryArc};
 
 mod bundle;
@@ -23,7 +26,7 @@ pub use resource::{ReflectResource, ReflectResourceFns};
 
 /// A [`Resource`] storing [`TypeRegistry`] for
 /// type registrations relevant to a whole app.
-#[derive(Resource, Clone, Default)]
+#[derive(Resource, Clone)]
 pub struct AppTypeRegistry(pub TypeRegistryArc);
 
 impl Deref for AppTypeRegistry {
@@ -42,6 +45,12 @@ impl DerefMut for AppTypeRegistry {
     }
 }
 
+impl FromWorld for AppTypeRegistry {
+    fn from_world(world: &mut World) -> Self {
+        Self(world.__type_registry().clone())
+    }
+}
+
 /// Creates a `T` from a `&dyn Reflect`.
 ///
 /// The first approach uses `T`'s implementation of `FromReflect`.

crates/bevy_ecs/src/world/mod.rs

@@ -44,6 +44,8 @@ use std::{
     sync::atomic::{AtomicU32, Ordering},
 };
 mod identifier;
+#[cfg(feature = "bevy_reflect")]
+use bevy_reflect::TypeRegistryArc;
 
 use self::unsafe_world_cell::{UnsafeEntityCell, UnsafeWorldCell};
 pub use identifier::WorldId;
@@ -153,6 +155,12 @@ impl World {
         World::default()
     }
 
+    #[doc(hidden)]
+    #[cfg(feature = "bevy_reflect")]
+    pub fn __type_registry(&self) -> &TypeRegistryArc {
+        &self.components().type_registry
+    }
+
     /// Retrieves this [`World`]'s unique ID
     #[inline]
     pub fn id(&self) -> WorldId {

crates/bevy_scene/src/dynamic_scene_builder.rs

@@ -380,9 +380,11 @@ mod tests {
     fn extract_one_entity() {
         let mut world = World::default();
 
-        let atr = AppTypeRegistry::default();
-        atr.write().register::<ComponentA>();
-        world.insert_resource(atr);
+        world.init_resource::<AppTypeRegistry>();
+        {
+            let mut register = world.resource::<AppTypeRegistry>().write();
+            register.register::<ComponentA>();
+        }
 
         let entity = world.spawn((ComponentA, ComponentB)).id();
 
@@ -400,9 +402,11 @@ mod tests {
     fn extract_one_entity_twice() {
         let mut world = World::default();
 
-        let atr = AppTypeRegistry::default();
-        atr.write().register::<ComponentA>();
-        world.insert_resource(atr);
+        world.init_resource::<AppTypeRegistry>();
+        {
+            let mut register = world.resource::<AppTypeRegistry>().write();
+            register.register::<ComponentA>();
+        }
 
         let entity = world.spawn((ComponentA, ComponentB)).id();
 
@@ -421,13 +425,12 @@ mod tests {
     fn extract_one_entity_two_components() {
         let mut world = World::default();
 
-        let atr = AppTypeRegistry::default();
+        world.init_resource::<AppTypeRegistry>();
         {
-            let mut register = atr.write();
+            let mut register = world.resource::<AppTypeRegistry>().write();
             register.register::<ComponentA>();
             register.register::<ComponentB>();
         }
-        world.insert_resource(atr);
 
         let entity = world.spawn((ComponentA, ComponentB)).id();
 
@@ -472,13 +475,12 @@ mod tests {
     fn extract_query() {
         let mut world = World::default();
 
-        let atr = AppTypeRegistry::default();
+        world.init_resource::<AppTypeRegistry>();
         {
-            let mut register = atr.write();
+            let mut register = world.resource::<AppTypeRegistry>().write();
             register.register::<ComponentA>();
             register.register::<ComponentB>();
         }
-        world.insert_resource(atr);
 
         let entity_a_b = world.spawn((ComponentA, ComponentB)).id();
         let entity_a = world.spawn(ComponentA).id();
@@ -499,9 +501,11 @@ mod tests {
     fn remove_componentless_entity() {
         let mut world = World::default();
 
-        let atr = AppTypeRegistry::default();
-        atr.write().register::<ComponentA>();
-        world.insert_resource(atr);
+        world.init_resource::<AppTypeRegistry>();
+        {
+            let mut register = world.resource::<AppTypeRegistry>().write();
+            register.register::<ComponentA>();
+        }
 
         let entity_a = world.spawn(ComponentA).id();
         let entity_b = world.spawn(ComponentB).id();
@@ -519,9 +523,11 @@ mod tests {
     fn extract_one_resource() {
         let mut world = World::default();
 
-        let atr = AppTypeRegistry::default();
-        atr.write().register::<ResourceA>();
-        world.insert_resource(atr);
+        world.init_resource::<AppTypeRegistry>();
+        {
+            let mut register = world.resource::<AppTypeRegistry>().write();
+            register.register::<ResourceA>();
+        }
 
         world.insert_resource(ResourceA);
 
@@ -537,9 +543,11 @@ mod tests {
     fn extract_one_resource_twice() {
         let mut world = World::default();
 
-        let atr = AppTypeRegistry::default();
-        atr.write().register::<ResourceA>();
-        world.insert_resource(atr);
+        world.init_resource::<AppTypeRegistry>();
+        {
+            let mut register = world.resource::<AppTypeRegistry>().write();
+            register.register::<ResourceA>();
+        }
 
         world.insert_resource(ResourceA);
 
@@ -555,14 +563,12 @@ mod tests {
     #[test]
     fn should_extract_allowed_components() {
         let mut world = World::default();
-
-        let atr = AppTypeRegistry::default();
+        world.init_resource::<AppTypeRegistry>();
         {
-            let mut register = atr.write();
+            let mut register = world.resource::<AppTypeRegistry>().write();
             register.register::<ComponentA>();
             register.register::<ComponentB>();
         }
-        world.insert_resource(atr);
 
         let entity_a_b = world.spawn((ComponentA, ComponentB)).id();
         let entity_a = world.spawn(ComponentA).id();
@@ -582,14 +588,12 @@ mod tests {
     #[test]
     fn should_not_extract_denied_components() {
         let mut world = World::default();
-
-        let atr = AppTypeRegistry::default();
+        world.init_resource::<AppTypeRegistry>();
         {
-            let mut register = atr.write();
+            let mut register = world.resource::<AppTypeRegistry>().write();
             register.register::<ComponentA>();
             register.register::<ComponentB>();
         }
-        world.insert_resource(atr);
 
         let entity_a_b = world.spawn((ComponentA, ComponentB)).id();
         let entity_a = world.spawn(ComponentA).id();
@@ -609,14 +613,12 @@ mod tests {
     #[test]
     fn should_extract_allowed_resources() {
         let mut world = World::default();
-
-        let atr = AppTypeRegistry::default();
+        world.init_resource::<AppTypeRegistry>();
         {
-            let mut register = atr.write();
+            let mut register = world.resource::<AppTypeRegistry>().write();
             register.register::<ResourceA>();
             register.register::<ResourceB>();
         }
-        world.insert_resource(atr);
 
         world.insert_resource(ResourceA);
         world.insert_resource(ResourceB);
@@ -633,14 +635,12 @@ mod tests {
     #[test]
     fn should_not_extract_denied_resources() {
         let mut world = World::default();
-
-        let atr = AppTypeRegistry::default();
+        world.init_resource::<AppTypeRegistry>();
         {
-            let mut register = atr.write();
+            let mut register = world.resource::<AppTypeRegistry>().write();
             register.register::<ResourceA>();
             register.register::<ResourceB>();
         }
-        world.insert_resource(atr);
 
         world.insert_resource(ResourceA);
         world.insert_resource(ResourceB);