fix crash where overwriting an existing component on the same frame as an entity was being destroyed would cause the component to not be destroyed

encompass-cs/ComponentManager.cs

@@ -105,7 +105,7 @@ namespace Encompass
                 var (entity, type) = keyValuePair.Key;
                 var (componentID, component) = keyValuePair.Value;
                 
-                if (!entityIDToComponentTypeToComponentID.ContainsKey(entity.ID)) { continue; }
+                if (!componentIDsMarkedForWrite.Contains(componentID) || !entityIDToComponentTypeToComponentID.ContainsKey(entity.ID)) { continue; }
 
                 if (entityIDToComponentTypeToComponentID[entity.ID].ContainsKey(type))
                 {
@@ -218,7 +218,7 @@ namespace Encompass
         {
             foreach (var componentID in componentsMarkedForRemoval)
             {
-                if (componentIDsMarkedForWrite.Contains(componentID))
+                if (componentIDsMarkedForWrite.Contains(componentID) && !IDToComponent.ContainsKey(componentID))
                 {
                     componentIDsMarkedForWrite.Remove(componentID);
                 }

test/EngineTest.cs

@@ -847,5 +847,49 @@ namespace Tests
 
             Assert.DoesNotThrow(() => world.Update(0.01));
         }
+
+        struct DestroyComponentMessage : IMessage { public Entity entity; }
+
+        [Reads(typeof(MockComponent))]
+        [Writes(typeof(MockComponent))]
+        class AddComponentEngine : Engine
+        {
+            public override void Update(double dt)
+            {
+                foreach (var (componentID, component) in ReadComponents<MockComponent>())
+                {
+                    SetComponent(componentID, new MockComponent {});
+                }
+            }
+        }
+
+        [Receives(typeof(DestroyComponentMessage))]
+        class DestroyEntityEngine : Engine
+        {
+            public override void Update(double dt)
+            {
+                foreach (var message in ReadMessages<DestroyComponentMessage>())
+                {
+                    Destroy(message.entity.ID);
+                }
+            }
+        }
+
+        [Test]
+        public void EngineSetComponentAndDestroyEntitySameFrame()
+        {
+            var worldBuilder = new WorldBuilder();
+            worldBuilder.AddEngine(new AddComponentEngine());
+            worldBuilder.AddEngine(new DestroyEntityEngine());
+
+            var entity = worldBuilder.CreateEntity();
+            worldBuilder.SetComponent(entity, new MockComponent {});
+            worldBuilder.SendMessage(new DestroyComponentMessage { entity = entity });
+
+            var world = worldBuilder.Build();
+            world.Update(0.01);
+            
+            Assert.DoesNotThrow(() => world.Update(0.01));
+        }
     }
 }