Remove all existing system order ambiguities in DefaultPlugins

crates/bevy_animation/src/lib.rs

@@ -1234,7 +1234,7 @@ impl Plugin for AnimationPlugin {
                 (
                     advance_transitions,
                     advance_animations,
-                    animate_targets,
+                    animate_targets.after(bevy_render::mesh::morph::inherit_weights),
                     expire_completed_transitions,
                 )
                     .chain()

crates/bevy_app/src/terminal_ctrl_c_handler.rs

@@ -48,7 +48,7 @@ impl TerminalCtrlCHandlerPlugin {
     }
 
     /// Sends a [`AppExit`] event when the user presses `Ctrl+C` on the terminal.
-    fn exit_on_flag(mut events: EventWriter<AppExit>) {
+    pub fn exit_on_flag(mut events: EventWriter<AppExit>) {
         if SHOULD_EXIT.load(Ordering::Relaxed) {
             events.send(AppExit::from_code(130));
         }

crates/bevy_asset/src/lib.rs

@@ -222,7 +222,11 @@ impl Plugin for AssetPlugin {
             .init_asset::<()>()
             .add_event::<UntypedAssetLoadFailedEvent>()
             .configure_sets(PreUpdate, TrackAssets.after(handle_internal_asset_events))
-            .add_systems(PreUpdate, handle_internal_asset_events)
+            // `handle_internal_asset_events` requires the use of `&mut World`,
+            // and as a result has ambiguous system ordering with all other systems in `PreUpdate`.
+            // This is virtually never a real problem: asset loading is async and so anything that interacts directly with it
+            // needs to be robust to stochastic delays anyways.
+            .add_systems(PreUpdate, handle_internal_asset_events.ambiguous_with_all())
             .register_type::<AssetPath>();
     }
 }

crates/bevy_dev_tools/src/ci_testing/mod.rs

@@ -6,7 +6,7 @@ mod systems;
 pub use self::config::*;
 
 use bevy_app::prelude::*;
-use bevy_ecs::schedule::IntoSystemConfigs;
+use bevy_ecs::prelude::*;
 use bevy_render::view::screenshot::trigger_screenshots;
 use bevy_time::TimeUpdateStrategy;
 use std::time::Duration;
@@ -54,7 +54,19 @@ impl Plugin for CiTestingPlugin {
                 Update,
                 systems::send_events
                     .before(trigger_screenshots)
-                    .before(bevy_window::close_when_requested),
+                    .before(bevy_window::close_when_requested)
+                    .in_set(SendEvents),
             );
+
+        // The offending system does not exist in the wasm32 target.
+        // As a result, we must conditionally order the two systems using a system set.
+        #[cfg(not(target_arch = "wasm32"))]
+        app.configure_sets(
+            Update,
+            SendEvents.before(bevy_app::TerminalCtrlCHandlerPlugin::exit_on_flag),
+        );
     }
 }
+
+#[derive(SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
+struct SendEvents;

crates/bevy_gizmos/src/aabb.rs

@@ -40,6 +40,7 @@ impl Plugin for AabbGizmoPlugin {
                         config.config::<AabbGizmoConfigGroup>().1.draw_all
                     }),
                 )
+                    .after(bevy_render::view::VisibilitySystems::CalculateBounds)
                     .after(TransformSystem::TransformPropagate),
             );
     }

crates/bevy_gizmos/src/lib.rs

@@ -242,6 +242,9 @@ impl AppGizmoBuilder for App {
         handles.list.insert(TypeId::of::<Config>(), None);
         handles.strip.insert(TypeId::of::<Config>(), None);
 
+        // These handles are safe to mutate in any order
+        self.allow_ambiguous_resource::<LineGizmoHandles>();
+
         self.init_resource::<GizmoStorage<Config, ()>>()
             .init_resource::<GizmoStorage<Config, Fixed>>()
             .init_resource::<GizmoStorage<Config, Swap<Fixed>>>()

crates/bevy_internal/src/default_plugins.rs

@@ -90,6 +90,11 @@ impl Plugin for IgnoreAmbiguitiesPlugin {
                 bevy_animation::advance_animations,
                 bevy_ui::ui_layout_system,
             );
+            app.ignore_ambiguity(
+                bevy_app::PostUpdate,
+                bevy_animation::animate_targets,
+                bevy_ui::ui_layout_system,
+            );
         }
     }
 }

crates/bevy_pbr/src/lib.rs

@@ -340,10 +340,22 @@ impl Plugin for PbrPlugin {
                 )
                     .chain(),
             )
+            .configure_sets(
+                PostUpdate,
+                SimulationLightSystems::UpdateDirectionalLightCascades
+                    .ambiguous_with(SimulationLightSystems::UpdateDirectionalLightCascades),
+            )
+            .configure_sets(
+                PostUpdate,
+                SimulationLightSystems::CheckLightVisibility
+                    .ambiguous_with(SimulationLightSystems::CheckLightVisibility),
+            )
             .add_systems(
                 PostUpdate,
                 (
-                    add_clusters.in_set(SimulationLightSystems::AddClusters),
+                    add_clusters
+                        .in_set(SimulationLightSystems::AddClusters)
+                        .after(CameraUpdateSystem),
                     assign_objects_to_clusters
                         .in_set(SimulationLightSystems::AssignLightsToClusters)
                         .after(TransformSystem::TransformPropagate)

crates/bevy_pbr/src/light/mod.rs

@@ -496,12 +496,19 @@ pub enum ShadowFilteringMethod {
     Temporal,
 }
 
+/// System sets used to run light-related systems.
 #[derive(Debug, Hash, PartialEq, Eq, Clone, SystemSet)]
 pub enum SimulationLightSystems {
     AddClusters,
     AssignLightsToClusters,
+    /// System order ambiguities between systems in this set are ignored:
+    /// each [`build_directional_light_cascades`] system is independent of the others,
+    /// and should operate on distinct sets of entities.
     UpdateDirectionalLightCascades,
     UpdateLightFrusta,
+    /// System order ambiguities between systems in this set are ignored:
+    /// the order of systems within this set is irrelevant, as the various visibility-checking systesms
+    /// assumes that their operations are irreversible during the frame.
     CheckLightVisibility,
 }
 

crates/bevy_picking/src/lib.rs

@@ -225,7 +225,6 @@ impl Plugin for PickingPlugin {
                 First,
                 (PickSet::Input, PickSet::PostInput)
                     .after(bevy_time::TimeSystem)
-                    .ambiguous_with(bevy_asset::handle_internal_asset_events)
                     .after(bevy_ecs::event::EventUpdates)
                     .chain(),
             )
@@ -239,7 +238,6 @@ impl Plugin for PickingPlugin {
                     // Eventually events will need to be dispatched here
                     PickSet::Last,
                 )
-                    .ambiguous_with(bevy_asset::handle_internal_asset_events)
                     .chain(),
             )
             .register_type::<pointer::PointerId>()

crates/bevy_render/src/view/visibility/mod.rs

@@ -278,7 +278,11 @@ pub enum VisibilitySystems {
     /// [`hierarchy`](bevy_hierarchy).
     VisibilityPropagate,
     /// Label for the [`check_visibility`] system updating [`ViewVisibility`]
-    /// of each entity and the [`VisibleEntities`] of each view.
+    /// of each entity and the [`VisibleEntities`] of each view.\
+    ///
+    /// System order ambiguities between systems in this set are ignored:
+    /// the order of systems within this set is irrelevant, as [`check_visibility`]
+    /// assumes that its operations are irreversible during the frame.
     CheckVisibility,
 }
 
@@ -294,6 +298,7 @@ impl Plugin for VisibilityPlugin {
                 .before(CheckVisibility)
                 .after(TransformSystem::TransformPropagate),
         )
+        .configure_sets(PostUpdate, CheckVisibility.ambiguous_with(CheckVisibility))
         .add_systems(
             PostUpdate,
             (

crates/bevy_ui/src/lib.rs

@@ -164,7 +164,9 @@ impl Plugin for UiPlugin {
                 update_target_camera_system.in_set(UiSystem::Prepare),
                 ui_layout_system
                     .in_set(UiSystem::Layout)
-                    .before(TransformSystem::TransformPropagate),
+                    .before(TransformSystem::TransformPropagate)
+                    // Text and Text2D operate on disjoint sets of entities
+                    .ambiguous_with(bevy_text::update_text2d_layout),
                 ui_stack_system
                     .in_set(UiSystem::Stack)
                     // the systems don't care about stack index
@@ -226,7 +228,8 @@ fn build_text_interop(app: &mut App) {
                 .in_set(UiSystem::PostLayout)
                 .after(bevy_text::remove_dropped_font_atlas_sets)
                 // Text2d and bevy_ui text are entirely on separate entities
-                .ambiguous_with(bevy_text::update_text2d_layout),
+                .ambiguous_with(bevy_text::update_text2d_layout)
+                .ambiguous_with(bevy_text::calculate_bounds_text2d),
         ),
     );
 

tests/ecs/ambiguity_detection.rs

@@ -9,18 +9,22 @@ use bevy::{
     prelude::*,
     utils::HashMap,
 };
-use bevy_render::{pipelined_rendering::RenderExtractApp, RenderApp};
+use bevy_render::pipelined_rendering::RenderExtractApp;
 
 fn main() {
     let mut app = App::new();
     app.add_plugins(DefaultPlugins);
 
-    let sub_app = app.main_mut();
-    configure_ambiguity_detection(sub_app);
-    let sub_app = app.sub_app_mut(RenderApp);
-    configure_ambiguity_detection(sub_app);
-    let sub_app = app.sub_app_mut(RenderExtractApp);
-    configure_ambiguity_detection(sub_app);
+    let main_app = app.main_mut();
+    configure_ambiguity_detection(main_app);
+    let render_extract_app = app.sub_app_mut(RenderExtractApp);
+    configure_ambiguity_detection(render_extract_app);
+
+    // Ambiguities in the RenderApp are currently allowed.
+    // Eventually, we should forbid these: see https://github.com/bevyengine/bevy/issues/7386
+    // Uncomment the lines below to show the current ambiguities in the RenderApp.
+    // let sub_app = app.sub_app_mut(bevy_render::RenderApp);
+    // configure_ambiguity_detection(sub_app);
 
     app.finish();
     app.cleanup();
@@ -29,11 +33,7 @@ fn main() {
     let main_app_ambiguities = count_ambiguities(app.main());
     assert_eq!(
         main_app_ambiguities.total(),
-        // This number *should* be zero.
-        // Over time, we are working to reduce the number: your PR should not increase it.
-        // If you decrease this by fixing an ambiguity, reduce the number to prevent regressions.
-        // See https://github.com/bevyengine/bevy/issues/7386 for progress.
-        44,
+        0,
         "Main app has unexpected ambiguities among the following schedules: \n{:#?}.",
         main_app_ambiguities,
     );