Remote entity reservation v2

crates/bevy_ecs/src/archetype.rs

@@ -50,6 +50,9 @@ impl ArchetypeRow {
     /// Index indicating an invalid archetype row.
     /// This is meant to be used as a placeholder.
     pub const INVALID: ArchetypeRow = ArchetypeRow(u32::MAX);
+    /// This is the same as [`Self::INVALID`], but it signals to [`Entities`](crate::entity::Entities)
+    /// that this entity should not be flushed.
+    pub(crate) const INVALID_BUT_DONT_FLUSH: ArchetypeRow = ArchetypeRow(u32::MAX - 1);
 
     /// Creates a `ArchetypeRow`.
     #[inline]

crates/bevy_ecs/src/entity/map_entities.rs

@@ -86,7 +86,7 @@ impl<T: VisitEntitiesMut> MapEntities for T {
 ///     fn get_mapped(&mut self, entity: Entity) -> Entity {
 ///         self.map.get(&entity).copied().unwrap_or(entity)
 ///     }
-///     
+///
 ///     fn set_mapped(&mut self, source: Entity, target: Entity) {
 ///         self.map.insert(source, target);
 ///     }
@@ -275,8 +275,8 @@ mod tests {
         );
 
         mapper.finish(&mut world);
-        // Next allocated entity should be a further generation on the same index
-        let entity = world.spawn_empty().id();
+        // Future allocated entity should be a further generation on the same index
+        let entity = world.entities().resolve_from_id(dead_ref.index()).unwrap();
         assert_eq!(entity.index(), dead_ref.index());
         assert!(entity.generation() > dead_ref.generation());
     }
@@ -290,8 +290,8 @@ mod tests {
             mapper.get_mapped(Entity::from_raw(0))
         });
 
-        // Next allocated entity should be a further generation on the same index
-        let entity = world.spawn_empty().id();
+        // Future allocated entity should be a further generation on the same index
+        let entity = world.entities().resolve_from_id(dead_ref.index()).unwrap();
         assert_eq!(entity.index(), dead_ref.index());
         assert!(entity.generation() > dead_ref.generation());
     }
@@ -301,15 +301,12 @@ mod tests {
         let mut world = World::new();
         // "Dirty" the `Entities`, requiring a flush afterward.
         world.entities.reserve_entity();
-        assert!(world.entities.needs_flush());
+        assert!(world.entities.worth_flushing());
 
         // Create and exercise a SceneEntityMapper - should not panic because it flushes
         // `Entities` first.
         SceneEntityMapper::world_scope(&mut Default::default(), &mut world, |_, m| {
             m.get_mapped(Entity::PLACEHOLDER);
         });
-
-        // The SceneEntityMapper should leave `Entities` in a flushed state.
-        assert!(!world.entities.needs_flush());
     }
 }