Discard old diffs on client

src/client.rs

@@ -1,5 +1,5 @@
 use bevy::{
-    ecs::{system::SystemState, world::EntityMut},
+    ecs::world::EntityMut,
     prelude::*,
     utils::{Entry, HashMap},
 };
@@ -45,17 +45,13 @@ impl Plugin for ClientPlugin {
 }
 
 impl ClientPlugin {
-    fn diff_receiving_system(world: &mut World, state: &mut SystemState<ResMut<RenetClient>>) {
-        let mut client = state.get_mut(world);
-        let mut last_message = None;
-        while let Some(message) = client.receive_message(REPLICATION_CHANNEL_ID) {
-            last_message = Some(message);
-        }
-
-        if let Some(last_message) = last_message {
-            WorldDiff::deserialize_to_world(world, last_message)
-                .expect("server should send only valid world diffs");
-        }
+    fn diff_receiving_system(world: &mut World) {
+        world.resource_scope(|world, mut client: Mut<RenetClient>| {
+            while let Some(message) = client.receive_message(REPLICATION_CHANNEL_ID) {
+                WorldDiff::deserialize_to_world(world, message)
+                    .expect("server should send only valid world diffs");
+            }
+        });
     }
 
     fn ack_sending_system(last_tick: Res<LastTick>, mut client: ResMut<RenetClient>) {

src/replicon_core.rs

@@ -343,17 +343,24 @@ impl WorldDiff<'_> {
     }
 
     /// Deserializes itself from bytes directly into the world by applying all changes.
+    ///
+    /// Does nothing if world already received a more recent diff.
+    /// See also [`LastTick`].
     pub(super) fn deserialize_to_world(
         world: &mut World,
         message: Bytes,
     ) -> Result<(), bincode::Error> {
-        world.resource_scope(|world, replication_rules: Mut<ReplicationRules>| {
-            world.resource_scope(|world, mut entity_map: Mut<NetworkEntityMap>| {
-                let mut cursor = Cursor::new(message);
+        let mut cursor = Cursor::new(message);
 
-                let tick = bincode::deserialize_from(&mut cursor)?;
-                world.resource_mut::<LastTick>().0 = tick;
+        let tick = bincode::deserialize_from(&mut cursor)?;
+        let mut last_tick = world.resource_mut::<LastTick>();
+        if last_tick.0 >= tick {
+            return Ok(());
+        }
+        last_tick.0 = tick;
 
+        world.resource_scope(|world, replication_rules: Mut<ReplicationRules>| {
+            world.resource_scope(|world, mut entity_map: Mut<NetworkEntityMap>| {
                 let entities_count: usize = bincode::deserialize_from(&mut cursor)?;
                 for _ in 0..entities_count {
                     let entity = bincode::deserialize_from(&mut cursor)?;