From 6741e01dfa8876a6113adb79bdd475982e4d3e80 Mon Sep 17 00:00:00 2001
From: andriyDev <andriydzikh@gmail.com>
Date: Thu, 21 Nov 2024 16:52:17 -0800
Subject: [PATCH] Fix adding a subtree of required components to an existing
 tree replacing shallower required component constructors (#16441)

# Objective

- Fixes #16406 even more. The previous implementation did not take into
account the depth of the requiree when setting the depth relative to the
required_by component.

## Solution

- Add the depth of the requiree!

## Testing

- Added a test.

---------

Co-authored-by: Carter Anderson <mcanders1@gmail.com>
---
 crates/bevy_ecs/src/component.rs |  9 ++++++---
 crates/bevy_ecs/src/lib.rs       | 34 ++++++++++++++++++++++++++++++++
 crates/bevy_ecs/src/world/mod.rs |  2 +-
 3 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/crates/bevy_ecs/src/component.rs b/crates/bevy_ecs/src/component.rs
index d3b72f5a3ad1d..b915f8b5cad09 100644
--- a/crates/bevy_ecs/src/component.rs
+++ b/crates/bevy_ecs/src/component.rs
@@ -1029,8 +1029,8 @@ impl Components {
     /// registration will be used.
     pub(crate) unsafe fn register_required_components<R: Component>(
         &mut self,
-        required: ComponentId,
         requiree: ComponentId,
+        required: ComponentId,
         constructor: fn() -> R,
     ) -> Result<(), RequiredComponentsError> {
         // SAFETY: The caller ensures that the `requiree` is valid.
@@ -1083,14 +1083,17 @@ impl Components {
 
                 for (component_id, component) in inherited_requirements.iter() {
                     // Register the required component.
-                    // The inheritance depth is increased by `1` since this is a component required by the original required component.
+                    // The inheritance depth of inherited components is whatever the requiree's
+                    // depth is relative to `required_by_id`, plus the inheritance depth of the
+                    // inherited component relative to the requiree, plus 1 to account for the
+                    // requiree in between.
                     // SAFETY: Component ID and constructor match the ones on the original requiree.
                     //         The original requiree is responsible for making sure the registration is safe.
                     unsafe {
                         required_components.register_dynamic(
                             *component_id,
                             component.constructor.clone(),
-                            component.inheritance_depth + 1,
+                            component.inheritance_depth + depth + 1,
                         );
                     };
                 }
diff --git a/crates/bevy_ecs/src/lib.rs b/crates/bevy_ecs/src/lib.rs
index 4eab4d00be690..3a2e24d904a32 100644
--- a/crates/bevy_ecs/src/lib.rs
+++ b/crates/bevy_ecs/src/lib.rs
@@ -2399,6 +2399,40 @@ mod tests {
         assert_eq!(world.entity(id).get::<Counter>().unwrap().0, 1);
     }
 
+    #[test]
+    fn runtime_required_components_deep_require_does_not_override_shallow_require_deep_subtree_after_shallow(
+    ) {
+        #[derive(Component)]
+        struct A;
+        #[derive(Component, Default)]
+        struct B;
+        #[derive(Component, Default)]
+        struct C;
+        #[derive(Component, Default)]
+        struct D;
+        #[derive(Component, Default)]
+        struct E;
+        #[derive(Component)]
+        struct Counter(i32);
+        #[derive(Component, Default)]
+        struct F;
+
+        let mut world = World::new();
+
+        world.register_required_components::<A, B>();
+        world.register_required_components::<B, C>();
+        world.register_required_components::<C, D>();
+        world.register_required_components::<D, E>();
+        world.register_required_components_with::<E, Counter>(|| Counter(1));
+        world.register_required_components_with::<F, Counter>(|| Counter(2));
+        world.register_required_components::<E, F>();
+
+        let id = world.spawn(A).id();
+
+        // The "shallower" of the two components is used.
+        assert_eq!(world.entity(id).get::<Counter>().unwrap().0, 1);
+    }
+
     #[test]
     fn runtime_required_components_existing_archetype() {
         #[derive(Component)]
diff --git a/crates/bevy_ecs/src/world/mod.rs b/crates/bevy_ecs/src/world/mod.rs
index eae555a0d56c4..63a3025eebc9b 100644
--- a/crates/bevy_ecs/src/world/mod.rs
+++ b/crates/bevy_ecs/src/world/mod.rs
@@ -515,7 +515,7 @@ impl World {
         // SAFETY: We just created the `required` and `requiree` components.
         unsafe {
             self.components
-                .register_required_components::<R>(required, requiree, constructor)
+                .register_required_components::<R>(requiree, required, constructor)
         }
     }