Fix replay playback bugs

RELEASE-NOTES.md

@@ -43,7 +43,7 @@ END TEMPLATE-->
 
 ### Bugfixes
 
-*None yet*
+* Fixed a state handling bug in replays, which was causing exceptions to be thrown when applying delta states.
 
 ### Other
 

Robust.Client/GameStates/ClientGameStateManager.cs

@@ -399,7 +399,7 @@ public void ApplyGameState()
 
                 using (_prof.Group("MergeImplicitData"))
                 {
-                    MergeImplicitData(createdEntities);
+                    GenerateImplicitStates(createdEntities);
                 }
 
                 if (_lastProcessedInput < curState.LastProcessedInput)
@@ -671,7 +671,7 @@ public void ResetPredictedEntities()
         ///     initial server state for any newly created entity. It does this by simply using the standard <see
         ///     cref="IEntityManager.GetComponentState"/>.
         /// </remarks>
-        private void MergeImplicitData(IEnumerable<NetEntity> createdEntities)
+        public void GenerateImplicitStates(IEnumerable<NetEntity> createdEntities)
         {
             var bus = _entityManager.EventBus;
 

Robust.Client/GameStates/IClientGameStateManager.cs

@@ -82,6 +82,12 @@ public interface IClientGameStateManager
         /// </summary>
         IEnumerable<NetEntity> ApplyGameState(GameState curState, GameState? nextState);
 
+        /// <summary>
+        ///     Generates implicit component states for newly created entities.
+        ///     This should always be called after running <see cref="ApplyGameState(GameState, GameState)"/>.
+        /// </summary>
+        void GenerateImplicitStates(IEnumerable<NetEntity> states);
+
         /// <summary>
         ///     Resets any entities that have changed while predicting future ticks.
         /// </summary>

Robust.Client/Replays/Loading/ReplayLoadManager.Start.cs

@@ -95,9 +95,21 @@ public async Task StartReplayAsync(ReplayData data, LoadReplayCallback callback)
         _gameState.ClearDetachQueue();
         _gameState.ApplyGameState(checkpoint.State, next);
 
+        // Sort entities to ensure that we initialize parents before children
+        var sorted = new List<EntityUid>(entities.Count);
+        var added = new HashSet<EntityUid>(entities.Count);
+        var xformQuery = _entMan.GetEntityQuery<TransformComponent>();
+        foreach (var uid in entities)
+        {
+            AddSorted(uid, sorted, added, xformQuery);
+        }
+        DebugTools.AssertEqual(sorted.Count, entities.Count);
+        DebugTools.AssertEqual(added.Count, entities.Count);
+        await callback(i, total, LoadingState.Initializing, false);
+
         i = 0;
         var query = _entMan.GetEntityQuery<MetaDataComponent>();
-        foreach (var uid in entities)
+        foreach (var uid in sorted)
         {
             _entMan.InitializeEntity(uid, query.GetComponent(uid));
             if (i++ % 50 == 0)
@@ -109,7 +121,7 @@ public async Task StartReplayAsync(ReplayData data, LoadReplayCallback callback)
 
         i = 0;
         await callback(0, total, LoadingState.Starting, true);
-        foreach (var uid in entities)
+        foreach (var uid in sorted)
         {
             _entMan.StartEntity(uid);
             if (i++ % 50 == 0)
@@ -132,4 +144,16 @@ public async Task StartReplayAsync(ReplayData data, LoadReplayCallback callback)
         _replayPlayback.StartReplay(data);
         _timing.Paused = false;
     }
+
+    private void AddSorted(EntityUid uid, List<EntityUid> sortedList, HashSet<EntityUid> added, EntityQuery<TransformComponent> query)
+    {
+        if (!added.Add(uid))
+            return;
+
+        var parent = query.Comp(uid).ParentUid;
+        if (parent != EntityUid.Invalid)
+            AddSorted(parent, sortedList, added, query);
+
+        sortedList.Add(uid);
+    }
 }

Robust.Client/Replays/Playback/ReplayPlaybackManager.Update.cs

@@ -44,7 +44,8 @@ private void TickUpdateOverride(FrameEventArgs args)
             _gameState.UpdateFullRep(state, cloneDelta: true);
             var next = Replay.NextState;
             BeforeApplyState?.Invoke((state, next));
-            _gameState.ApplyGameState(state, next);
+            var created = _gameState.ApplyGameState(state, next);
+            _gameState.GenerateImplicitStates(created);
             DebugTools.Assert(Replay.LastApplied >= state.FromSequence);
             DebugTools.Assert(Replay.LastApplied + 1 <= state.ToSequence);
             Replay.LastApplied = state.ToSequence;

Robust.Shared/GameObjects/ComponentState.cs

@@ -40,17 +40,17 @@ public interface IComponentDeltaState<TState> : IComponentDeltaState where TStat
 
     void IComponentDeltaState.ApplyToFullState(IComponentState fullState)
     {
-        if (fullState is TState state)
-            ApplyToFullState(state);
-        else
-            throw new Exception($"Unexpected type. Expected {nameof(TState)} but got {fullState.GetType().Name}");
+        if (fullState is not TState state)
+            throw new Exception($"Unexpected type. Expected {typeof(TState).Name} but got {fullState.GetType().Name}");
+
+        ApplyToFullState(state);
     }
 
     IComponentState IComponentDeltaState.CreateNewFullState(IComponentState fullState)
     {
-        if (fullState is TState state)
-            return CreateNewFullState(state);
-        else
-            throw new Exception($"Unexpected type. Expected {nameof(TState)} but got {fullState.GetType().Name}");
+        if (fullState is not TState state)
+            throw new Exception($"Unexpected type. Expected {typeof(TState).Name} but got {fullState.GetType().Name}");
+
+        return CreateNewFullState(state);
     }
 }