From b6ed9e5f83f06cf3323f2ad18a70c593b072e6f5 Mon Sep 17 00:00:00 2001
From: Meta Vens <rwvens@hotmail.com>
Date: Mon, 14 Sep 2026 13:43:45 +0200
Subject: [PATCH] Cover GetByIndex resolving through assignable types

GetByIndexMatchesAssignableTypes: a [CultIndex] on a base member of two
derived documents resolves GetByIndex<Base> to the derived record, throws
naming both keys once the value is ambiguous across the two types, and
still resolves by the concrete type. GetByIndex<T> already filtered
assignable types; no CultCache change.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 .../StoreRoutingTests.cs                      | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/tests/GameCult.Caching.Tests/StoreRoutingTests.cs b/tests/GameCult.Caching.Tests/StoreRoutingTests.cs
index 9a65dc89..fc99f01f 100644
--- a/tests/GameCult.Caching.Tests/StoreRoutingTests.cs
+++ b/tests/GameCult.Caching.Tests/StoreRoutingTests.cs
@@ -410,6 +410,22 @@ namespace GameCult.Caching.Tests
             Assert.That(reader.AllEntries, Is.Empty);
         }
 
+        [Test]
+        public async Task GetByIndexMatchesAssignableTypes()
+        {
+            using var cache = new CultCache(CultDocumentRegistry.ForTypes(new[] { typeof(RoutingIndexedLeaf), typeof(RoutingIndexedTwin) }));
+            var leaf = await cache.UpsertAsync(typeof(RoutingIndexedLeaf), new RoutingIndexedLeaf { Code = "alpha" });
+
+            Assert.That(cache.GetByIndex<RoutingIndexedBase>("code", "alpha"), Is.InstanceOf<RoutingIndexedLeaf>(),
+                "an index declared on a base member resolves through the base type");
+
+            var twin = await cache.UpsertAsync(typeof(RoutingIndexedTwin), new RoutingIndexedTwin { Code = "alpha" });
+
+            Assert.That(() => cache.GetByIndex<RoutingIndexedBase>("code", "alpha"),
+                Throws.InvalidOperationException.With.Message.Contains(leaf.Value).And.Message.Contains(twin.Value));
+            Assert.That(cache.GetByIndex<RoutingIndexedLeaf>("code", "alpha"), Is.InstanceOf<RoutingIndexedLeaf>());
+        }
+
         [Test]
         public async Task AmbiguousAssignableLookupThrows()
         {
@@ -768,6 +784,25 @@ namespace GameCult.Caching.Tests
             public string Name = string.Empty;
         }
 
+        internal abstract class RoutingIndexedBase
+        {
+            [Key(0)]
+            [CultIndex("code")]
+            public string Code = string.Empty;
+        }
+
+        [CultDocument("tests.routing_indexed_leaf", "tests.routing_indexed_leaf.v1")]
+        [MessagePackObject(AllowPrivate = true)]
+        internal sealed class RoutingIndexedLeaf : RoutingIndexedBase
+        {
+        }
+
+        [CultDocument("tests.routing_indexed_twin", "tests.routing_indexed_twin.v1")]
+        [MessagePackObject(AllowPrivate = true)]
+        internal sealed class RoutingIndexedTwin : RoutingIndexedBase
+        {
+        }
+
         internal abstract class RoutingGlobalBase
         {
         }