From 96e09f004b24d257781ba0aa715c2904def5d56a Mon Sep 17 00:00:00 2001 From: Ida Iyes Date: Mon, 21 Nov 2022 14:23:21 +0000 Subject: [PATCH] Fix PipeSystem panicking with exclusive systems (#6698) Without this fix, piped systems containing exclusive systems fail to run, giving a runtime panic. With this PR, running piped systems that contain exclusive systems now works. ## Explanation of the bug This is because, unless overridden, the default implementation of `run` from the `System` trait simply calls `run_unsafe`. That is not valid for exclusive systems. They must always be called via `run`, as `run_unsafe` takes `&World` instead of `&mut World`. Trivial reproduction example: ```rust fn main() { App::new() .add_plugins(DefaultPlugins) .add_system(exclusive.pipe(another)) .run(); } fn exclusive(_world: &mut World) {} fn another() {} ``` If you run this, you will get a panic 'Cannot run exclusive systems with a shared World reference' and the backtrace shows how bevy (correctly) tries to call the `run` method (because the system is exclusive), but it is the implementation from the `System` trait (because `PipeSystem` does not have its own), which calls `run_unsafe` (incorrect): - 3: as bevy_ecs::system::system::System>::run_unsafe - 4: bevy_ecs::system::system::System::run --- crates/bevy_ecs/src/system/system_piping.rs | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/crates/bevy_ecs/src/system/system_piping.rs b/crates/bevy_ecs/src/system/system_piping.rs index c9be4096c7..09533a02c3 100644 --- a/crates/bevy_ecs/src/system/system_piping.rs +++ b/crates/bevy_ecs/src/system/system_piping.rs @@ -83,6 +83,12 @@ impl> System for PipeSystem< self.system_b.run_unsafe(out, world) } + // needed to make exclusive systems work + fn run(&mut self, input: Self::In, world: &mut World) -> Self::Out { + let out = self.system_a.run(input, world); + self.system_b.run(out, world) + } + fn apply_buffers(&mut self, world: &mut World) { self.system_a.apply_buffers(world); self.system_b.apply_buffers(world);