From dcffedc18e1227af27b9d008b034c29dfd8825a5 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Fri, 6 May 2022 18:52:26 +0000
Subject: [PATCH] Apply buffers in `ParamSet` (#4677)

# Objective

- Fix https://github.com/bevyengine/bevy/issues/4676

## Solution

- Fixes https://github.com/bevyengine/bevy/issues/4676
- I have no reason to think this isn't sound, but `ParamSet` is a bit spooky
---
 crates/bevy_ecs/macros/src/lib.rs |  4 ++++
 crates/bevy_ecs/src/system/mod.rs | 21 ++++++++++++++++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/crates/bevy_ecs/macros/src/lib.rs b/crates/bevy_ecs/macros/src/lib.rs
index f67ce35bbb997c..0f57f448a18e7c 100644
--- a/crates/bevy_ecs/macros/src/lib.rs
+++ b/crates/bevy_ecs/macros/src/lib.rs
@@ -250,6 +250,10 @@ pub fn impl_param_set(_input: TokenStream) -> TokenStream {
                         #param.new_archetype(archetype, system_meta);
                     )*
                 }
+
+                fn apply(&mut self, world: &mut World) {
+                    self.0.apply(world)
+                }
             }
 
 
diff --git a/crates/bevy_ecs/src/system/mod.rs b/crates/bevy_ecs/src/system/mod.rs
index 52d8b0a12d6f93..541cd674be935b 100644
--- a/crates/bevy_ecs/src/system/mod.rs
+++ b/crates/bevy_ecs/src/system/mod.rs
@@ -103,7 +103,7 @@ mod tests {
         query::{Added, Changed, Or, With, Without},
         schedule::{Schedule, Stage, SystemStage},
         system::{
-            IntoExclusiveSystem, IntoSystem, Local, NonSend, NonSendMut, ParamSet, Query,
+            Commands, IntoExclusiveSystem, IntoSystem, Local, NonSend, NonSendMut, ParamSet, Query,
             RemovedComponents, Res, ResMut, System, SystemState,
         },
         world::{FromWorld, World},
@@ -906,4 +906,23 @@ mod tests {
             expected_ids
         );
     }
+
+    #[test]
+    fn commands_param_set() {
+        // Regression test for #4676
+        let mut world = World::new();
+        let entity = world.spawn().id();
+
+        run_system(
+            &mut world,
+            move |mut commands_set: ParamSet<(Commands, Commands)>| {
+                commands_set.p0().entity(entity).insert(A);
+                commands_set.p1().entity(entity).insert(B);
+            },
+        );
+
+        let entity = world.entity(entity);
+        assert!(entity.contains::<A>());
+        assert!(entity.contains::<B>());
+    }
 }