ECS - add runtime assertion for missing indexed component values

Author: friflo

src/ECS/Index/Indexes/EntityIndex.cs

@@ -85,6 +85,9 @@ internal override void RemoveEntityFromIndex(int id, Archetype archetype, int co
         map.TryGetValue(linkedEntity, out var idArray);
         var idSpan  = idArray.GetSpan(heap, store);
         int index   = idSpan.IndexOf(id);
+        if (index == -1) {
+            StoreIndex.ThrowIndexedComponentValueNotFound();
+        }
         idArray.RemoveAt(index, heap);
         if (idArray.Count == 0) {
             map.Remove(linkedEntity);

src/ECS/Index/Indexes/RangeIndex.cs

@@ -65,6 +65,9 @@ internal override void RemoveEntityFromIndex(int id, Archetype archetype, int co
         map.TryGetValue(value, out var idArray);
         var idSpan  = idArray.GetSpan(heap, store);
         var index   = idSpan.IndexOf(id);
+        if (index == -1) {
+            StoreIndex.ThrowIndexedComponentValueNotFound();
+        }
         idArray.RemoveAt(index, heap);
         if (idArray.Count == 0) {
             map.Remove(value);

src/ECS/Index/Indexes/ValueClassIndex.cs

@@ -58,6 +58,9 @@ internal override void RemoveEntityFromIndex(int id, Archetype archetype, int co
         map.TryGetValue(value, out var idArray);
         var idSpan  = idArray.GetSpan(heap, store);
         var index   = idSpan.IndexOf(id);
+        if (index == -1) {
+            StoreIndex.ThrowIndexedComponentValueNotFound();
+        }
         idArray.RemoveAt(index, heap);
         if (idArray.Count == 0) {
             map.Remove(value);

src/ECS/Index/Indexes/ValueStructIndex.cs

@@ -56,6 +56,9 @@ internal override void RemoveEntityFromIndex(int id, Archetype archetype, int co
         map.TryGetValue(value, out var idArray);
         var idSpan  = idArray.GetSpan(heap, store);
         var index   = idSpan.IndexOf(id);
+        if (index == -1) {
+            StoreIndex.ThrowIndexedComponentValueNotFound();
+        }
         idArray.RemoveAt(index, heap);
         if (idArray.Count == 0) {
             map.Remove(value);

src/ECS/Index/Internal/StoreIndex.cs

@@ -2,6 +2,9 @@
 // See LICENSE file in the project root for full license information.
 
 // ReSharper disable once CheckNamespace
+
+using System;
+
 namespace Friflo.Engine.ECS.Index;
 
 internal static class StoreIndex
@@ -52,4 +55,8 @@ private static AbstractComponentIndex[] CreateStoreIndexMap()
         var schema = EntityStoreBase.Static.EntitySchema;
         return new AbstractComponentIndex[schema.maxIndexedStructIndex];
     }
+    
+    internal static void ThrowIndexedComponentValueNotFound() {
+        throw new InvalidOperationException("Indexed component value not found. Reason: indexed values mus not be changed. See: https://friflo.gitbook.io/friflo.engine.ecs/documentation/component-index#indexed-components");
+    }
 }

src/Tests/ECS/Index/Test_Index_Delete.cs

@@ -1,4 +1,5 @@
-using Friflo.Engine.ECS;
+using System;
+using Friflo.Engine.ECS;
 using NUnit.Framework;
 using static NUnit.Framework.Assert;
 
@@ -177,6 +178,21 @@ public static void Test_Index_Delete_Range()
         entity3.DeleteEntity();
         AreEqual("{ }",         values.Debug());
     }
+    
+    [Test]
+    public static void TestDeleteEntity() {
+        var store   = new EntityStore();
+        var root    = store.CreateEntity(1);
+        var entity2 = store.CreateEntity(2);
+        var entity3 = store.CreateEntity(3);
+        var child   = store.CreateEntity(new AttackComponent { target = entity2 });
+        child.GetComponent<AttackComponent>().target = entity3;   // causes subsequent exception. The indexed value MUST never be changed
+        root.AddChild(child);
+        var e = Throws<InvalidOperationException>(() => {
+            child.DeleteEntity();    
+        });
+        AreEqual("Indexed component value not found. Reason: indexed values mus not be changed. See: https://friflo.gitbook.io/friflo.engine.ecs/documentation/component-index#indexed-components", e!.Message);
+    }
 }
 
 }