Fix IsSelectedPatternValidation to reference field from pattern type and add test

src/HotChocolate/Core/src/Types/Configuration/Validation/IsSelectedPatternValidation.cs

@@ -20,7 +20,7 @@ public void Validate(
 
         foreach (var pattern in feature.Patterns)
         {
-            var objectField = schema.QueryType.Fields[pattern.FieldName];
+            var objectField = pattern.Type.Fields[pattern.FieldName];
             var validationContext = new ValidateIsSelectedPatternContext(schema, objectField, pattern.Pattern);
             ValidateIsSelectedPatternVisitor.Instance.Visit(pattern.Pattern, validationContext);
 

src/HotChocolate/Core/test/Types.Tests/Resolvers/IsSelectedTests.cs

@@ -851,6 +851,30 @@ public async Task IsSelected_Pattern_Root_Lists()
         result.MatchMarkdownSnapshot();
     }
 
+    [Fact]
+    public async Task IsSelected_Pattern_On_NonQueryType_Should_Build_Schema()
+    {
+        // Arrange & Act - should not throw KeyNotFoundException
+        var result =
+            await new ServiceCollection()
+                .AddGraphQL()
+                .AddQueryType<QueryWithNestedIsSelected>()
+                .ExecuteRequestAsync(
+                    """
+                    query {
+                        metrics {
+                            latency {
+                                dataset {
+                                    p50
+                                }
+                            }
+                        }
+                    }
+                    """);
+
+        result.MatchMarkdownSnapshot();
+    }
+
     public class Query
     {
         public static User DummyUser { get; } =
@@ -1141,4 +1165,24 @@ public class Audit
     public record Book(string Title, Author Author);
 
     public record Author(string Name);
+
+    public sealed record MetricsInnerData(double P50, double P95);
+
+    public sealed record MetricsOuterGraph(List<MetricsInnerData> Dataset);
+
+    public class MetricsType
+    {
+        public MetricsOuterGraph? GetLatency(
+            [IsSelected("dataset { p50 }")] bool isP50Selected,
+            IResolverContext context)
+        {
+            ((IMiddlewareContext)context).OperationResult.SetExtension("isSelected", isP50Selected);
+            return null;
+        }
+    }
+
+    public class QueryWithNestedIsSelected
+    {
+        public MetricsType GetMetrics() => new();
+    }
 }

src/HotChocolate/Core/test/Types.Tests/Resolvers/__snapshots__/IsSelectedTests.IsSelected_Pattern_On_NonQueryType_Should_Build_Schema.md

@@ -0,0 +1,14 @@
+# IsSelected_Pattern_On_NonQueryType_Should_Build_Schema
+
+```json
+{
+  "data": {
+    "metrics": {
+      "latency": null
+    }
+  },
+  "extensions": {
+    "isSelected": true
+  }
+}
+```