Move SystemRegistry to a field on World

crates/bevy_ecs/src/system/system_registry.rs

@@ -13,8 +13,8 @@ use crate::world::{Mut, World};
 ///
 /// Any [`Commands`](crate::system::Commands) generated by these systems (but not other systems), will immediately be applied.
 ///
-/// This type is stored as a [`Resource`](crate::system::Resource) on each [`World`], initialized by default.
-/// However, it will likely be easier to use the corresponding methods on [`World`],
+/// This type is stored as a field on each [`World`].
+/// Geneerally speaking, you should use the corresponding methods on [`World`],
 /// to avoid having to worry about split mutable borrows yourself.
 ///
 /// # Limitations
@@ -293,9 +293,7 @@ impl World {
         system: S,
         label: L,
     ) {
-        self.resource_scope(|world, mut registry: Mut<SystemRegistry>| {
-            registry.register_system(world, system, label);
-        });
+        self.system_registry.register_system(self, system, label);
     }
 
     pub fn register_system_with_labels<
@@ -308,9 +306,8 @@ impl World {
         system: S,
         labels: LI,
     ) {
-        self.resource_scope(|world, mut registry: Mut<SystemRegistry>| {
-            registry.register_system_with_labels(world, system, labels);
-        });
+        self.system_registry
+            .register_system_with_labels(self, system, labels);
     }
 
     /// Runs the supplied system on the [`World`] a single time
@@ -325,9 +322,7 @@ impl World {
     /// at once, and want parallel execution of these systems.
     #[inline]
     pub fn run_system<Params, S: IntoSystem<(), (), Params> + 'static>(&mut self, system: S) {
-        self.resource_scope(|world, mut registry: Mut<SystemRegistry>| {
-            registry.run_system(world, system);
-        });
+        self.system_registry.run_system(self, system);
     }
 
     /// Runs the system corresponding to the supplied [`SystemLabel`] on the [`World`] a single time
@@ -344,9 +339,7 @@ impl World {
     /// at once, and want parallel execution of these systems.
     #[inline]
     pub fn run_systems_by_label<L: SystemLabel>(&mut self, label: L) {
-        self.resource_scope(|world, mut registry: Mut<SystemRegistry>| {
-            registry.run_systems_by_label(world, label);
-        });
+        self.system_registry.run_systems_by_label(self, label);
     }
 }
 

crates/bevy_ecs/src/world/mod.rs

@@ -83,16 +83,20 @@ pub struct World {
     pub(crate) storages: Storages,
     pub(crate) bundles: Bundles,
     pub(crate) removed_components: SparseSet<ComponentId, Vec<Entity>>,
-    /// Access cache used by [WorldCell].
+    /// Access cache used by [`WorldCell`].
     pub(crate) archetype_component_access: ArchetypeComponentAccess,
     main_thread_validator: MainThreadValidator,
     pub(crate) change_tick: AtomicU32,
     pub(crate) last_change_tick: u32,
+    /// Stores the systems associated with this [`World`],
+    ///
+    /// These system can be manually run using [`World::run_system`].
+    pub system_registry: SystemRegistry,
 }
 
 impl Default for World {
     fn default() -> Self {
-        let mut world = Self {
+        World {
             id: WorldId::new().expect("More `bevy` `World`s have been created than is supported"),
             entities: Default::default(),
             components: Default::default(),
@@ -106,10 +110,8 @@ impl Default for World {
             // are detected on first system runs and for direct world queries.
             change_tick: AtomicU32::new(1),
             last_change_tick: 0,
-        };
-        // This resource is required by bevy_ecs itself, so cannot be included in a plugin
-        world.init_resource::<SystemRegistry>();
-        world
+            system_registry: Default::default(),
+        }
     }
 }