Pass query change ticks to QueryParIter instead of always using change ticks from World. (#8029)

Co-authored-by: Chris Russell <8494645+chescock@users.noreply.github.com>
Co-authored-by: James Liu <contact@jamessliu.com>

crates/bevy_ecs/src/query/mod.rs

@@ -61,8 +61,9 @@ impl<T> DebugCheckedUnwrap for Option<T> {
 #[cfg(test)]
 mod tests {
     use super::{ReadOnlyWorldQuery, WorldQuery};
-    use crate::prelude::{AnyOf, Entity, Or, QueryState, With, Without};
+    use crate::prelude::{AnyOf, Changed, Entity, Or, QueryState, With, Without};
     use crate::query::{ArchetypeFilter, QueryCombinationIter};
+    use crate::schedule::{IntoSystemConfigs, Schedule};
     use crate::system::{IntoSystem, Query, System, SystemState};
     use crate::{self as bevy_ecs, component::Component, world::World};
     use std::any::type_name;
@@ -749,4 +750,33 @@ mod tests {
         let _: [&Foo; 1] = q.many([e]);
         let _: &Foo = q.single();
     }
+
+    // regression test for https://github.com/bevyengine/bevy/pull/8029
+    #[test]
+    fn par_iter_mut_change_detection() {
+        let mut world = World::new();
+        world.spawn((A(1), B(1)));
+
+        fn propagate_system(mut query: Query<(&A, &mut B), Changed<A>>) {
+            query.par_iter_mut().for_each_mut(|(a, mut b)| {
+                b.0 = a.0;
+            });
+        }
+
+        fn modify_system(mut query: Query<&mut A>) {
+            for mut a in &mut query {
+                a.0 = 2;
+            }
+        }
+
+        let mut schedule = Schedule::new();
+        schedule.add_systems((propagate_system, modify_system).chain());
+        schedule.run(&mut world);
+        world.clear_trackers();
+        schedule.run(&mut world);
+        world.clear_trackers();
+
+        let values = world.query::<&B>().iter(&world).collect::<Vec<&B>>();
+        assert_eq!(values, vec![&B(2)]);
+    }
 }

crates/bevy_ecs/src/query/par_iter.rs

@@ -1,4 +1,4 @@
-use crate::world::World;
+use crate::{component::Tick, world::World};
 use bevy_tasks::ComputeTaskPool;
 use std::ops::Range;
 
@@ -81,6 +81,8 @@ impl BatchingStrategy {
 pub struct QueryParIter<'w, 's, Q: WorldQuery, F: ReadOnlyWorldQuery> {
     pub(crate) world: &'w World,
     pub(crate) state: &'s QueryState<Q, F>,
+    pub(crate) last_run: Tick,
+    pub(crate) this_run: Tick,
     pub(crate) batching_strategy: BatchingStrategy,
 }
 
@@ -148,12 +150,8 @@ impl<'w, 's, Q: WorldQuery, F: ReadOnlyWorldQuery> QueryParIter<'w, 's, Q, F> {
     ) {
         let thread_count = ComputeTaskPool::get().thread_num();
         if thread_count <= 1 {
-            self.state.for_each_unchecked_manual(
-                self.world,
-                func,
-                self.world.last_change_tick(),
-                self.world.read_change_tick(),
-            );
+            self.state
+                .for_each_unchecked_manual(self.world, func, self.last_run, self.this_run);
         } else {
             // Need a batch size of at least 1.
             let batch_size = self.get_batch_size(thread_count).max(1);
@@ -161,8 +159,8 @@ impl<'w, 's, Q: WorldQuery, F: ReadOnlyWorldQuery> QueryParIter<'w, 's, Q, F> {
                 self.world,
                 batch_size,
                 func,
-                self.world.last_change_tick(),
-                self.world.read_change_tick(),
+                self.last_run,
+                self.this_run,
             );
         }
     }

crates/bevy_ecs/src/query/state.rs

@@ -820,6 +820,8 @@ impl<Q: WorldQuery, F: ReadOnlyWorldQuery> QueryState<Q, F> {
         QueryParIter {
             world,
             state: self,
+            last_run: world.last_change_tick(),
+            this_run: world.read_change_tick(),
             batching_strategy: BatchingStrategy::new(),
         }
     }
@@ -832,9 +834,12 @@ impl<Q: WorldQuery, F: ReadOnlyWorldQuery> QueryState<Q, F> {
     #[inline]
     pub fn par_iter_mut<'w, 's>(&'s mut self, world: &'w mut World) -> QueryParIter<'w, 's, Q, F> {
         self.update_archetypes(world);
+        let this_run = world.change_tick();
         QueryParIter {
             world,
             state: self,
+            last_run: world.last_change_tick(),
+            this_run,
             batching_strategy: BatchingStrategy::new(),
         }
     }

crates/bevy_ecs/src/system/query.rs

@@ -728,6 +728,8 @@ impl<'w, 's, Q: WorldQuery, F: ReadOnlyWorldQuery> Query<'w, 's, Q, F> {
         QueryParIter {
             world: self.world,
             state: self.state.as_readonly(),
+            last_run: self.last_run,
+            this_run: self.this_run,
             batching_strategy: BatchingStrategy::new(),
         }
     }
@@ -742,6 +744,8 @@ impl<'w, 's, Q: WorldQuery, F: ReadOnlyWorldQuery> Query<'w, 's, Q, F> {
         QueryParIter {
             world: self.world,
             state: self.state,
+            last_run: self.last_run,
+            this_run: self.this_run,
             batching_strategy: BatchingStrategy::new(),
         }
     }