Consolidate STJ polymorphism tests into a shared abstract suite

src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/PolymorphicTests.CustomTypeHierarchies.cs → src/libraries/System.Text.Json/tests/Common/PolymorphicTests.CustomTypeHierarchies.cs

@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections;
@@ -9,6 +9,7 @@
 using System.Text.Encodings.Web;
 using System.Text.Json.Serialization.Metadata;
 using System.Threading.Tasks;
+using Microsoft.DotNet.XUnitExtensions;
 using Xunit;
 
 namespace System.Text.Json.Serialization.Tests
@@ -1078,14 +1079,14 @@ public async Task NestedPolymorphicClassesIncreaseReadAndWriteStackWhenNeeded()
 
         [JsonDerivedType(typeof(TestNodeList), "NodeList")]
         [JsonDerivedType(typeof(TestLeaf), "Leaf")]
-        abstract class TestNode
+        public abstract class TestNode
         {
             public string Name { get; set; }
 
             public abstract void AssertEqualTo(TestNode other);
         }
 
-        class TestNodeList : TestNode
+        public class TestNodeList : TestNode
         {
             public string Info { get; set; }
 
@@ -1118,7 +1119,7 @@ public override void AssertEqualTo(TestNode other)
             }
         }
 
-        class TestLeaf : TestNode
+        public class TestLeaf : TestNode
         {
             public string? Test { get; set; }
 
@@ -2477,9 +2478,18 @@ public class PolymorphicClassWithoutDerivedTypeAttribute
         {
         }
 
-        [Fact]
+        [ConditionalFact]
         public async Task PolymorphicClassWithNullDerivedTypeAttribute_ThrowsInvalidOperationException()
         {
+            if (Serializer.IsSourceGeneratedSerializer)
+            {
+                // The JsonDerivedType ctor arg is dereferenced without a null check in
+                // JsonSourceGenerator.Parser.cs, so the generator throws NRE rather than emitting
+                // a SYSLIB diagnostic. Pending a generator fix, the runtime InvalidOperationException
+                // is validated under reflection only.
+                throw new SkipTestException("Generator NRE on [JsonDerivedType(null)] prevents reaching the runtime path.");
+            }
+
             var value = new PolymorphicClassWithNullDerivedTypeAttribute();
             await Assert.ThrowsAsync<InvalidOperationException>(() => Serializer.SerializeWrapper(value));
         }
@@ -2656,9 +2666,14 @@ public class DerivedClass : PolymorphicGenericClass<T>
             }
         }
 
-        [Fact]
+        [ConditionalFact]
         public async Task PolymorphicDerivedGenericClass_ThrowsInvalidOperationException()
         {
+            if (Serializer.IsSourceGeneratedSerializer)
+            {
+                throw new SkipTestException("Source generator rejects this invalid polymorphic configuration at build time (SYSLIB diagnostic); the runtime InvalidOperationException is validated under reflection only.");
+            }
+
             PolymorphicDerivedGenericClass value = new PolymorphicDerivedGenericClass.DerivedClass<int>();
             await Assert.ThrowsAsync<InvalidOperationException>(() => Serializer.SerializeWrapper(value));
         }
@@ -2842,9 +2857,14 @@ public async Task OpenGenericDerivedType_DifferentTypeArguments_ProduceDifferent
             JsonTestHelper.AssertJsonEqual("""{"$type":"derived","Value":"hello"}""", strJson);
         }
 
-        [Fact]
+        [ConditionalFact]
         public async Task OpenGenericDerivedType_NonGenericBase_ThrowsInvalidOperationException()
         {
+            if (Serializer.IsSourceGeneratedSerializer)
+            {
+                throw new SkipTestException("Source generator rejects this invalid polymorphic configuration at build time (SYSLIB diagnostic); the runtime InvalidOperationException is validated under reflection only.");
+            }
+
             var value = new NonGenericBaseWithOpenGenericDerived();
             await Assert.ThrowsAsync<InvalidOperationException>(() => Serializer.SerializeWrapper(value));
         }
@@ -2855,9 +2875,14 @@ public class NonGenericBaseWithOpenGenericDerived
             public class OpenDerived<T> : NonGenericBaseWithOpenGenericDerived;
         }
 
-        [Fact]
+        [ConditionalFact]
         public async Task OpenGenericDerivedType_TypeArgsNotResolvable_ThrowsInvalidOperationException()
         {
+            if (Serializer.IsSourceGeneratedSerializer)
+            {
+                throw new SkipTestException("Source generator rejects this invalid polymorphic configuration at build time (SYSLIB diagnostic); the runtime InvalidOperationException is validated under reflection only.");
+            }
+
             // Derived<T> : Base<int> - T cannot be determined from Base<int>
             var value = new OpenGenericBase_Unresolvable<int>();
             await Assert.ThrowsAsync<InvalidOperationException>(() => Serializer.SerializeWrapper(value));
@@ -2871,9 +2896,14 @@ public class OpenGenericBase_Unresolvable<T>
 
         public class OpenGenericDerived_Unresolvable<T> : OpenGenericBase_Unresolvable<int>;
 
-        [Fact]
+        [ConditionalFact]
         public async Task OpenGenericDerivedType_GroundMismatchAgainstClosedBase_ThrowsInvalidOperationException()
         {
+            if (Serializer.IsSourceGeneratedSerializer)
+            {
+                throw new SkipTestException("Source generator rejects this invalid polymorphic configuration at build time (SYSLIB diagnostic); the runtime InvalidOperationException is validated under reflection only.");
+            }
+
             // OpenGenericDerived_GroundMismatch<T> : OpenGenericBase_GroundMismatch<T, int>
             // registered on OpenGenericBase_GroundMismatch<int, string>.
             // Position 0 (T) unifies with int, but position 1 (concrete int in derived's base
@@ -3174,9 +3204,14 @@ public class OpenGenericDerived_Tuple<T1, T2> : OpenGenericBase_Tuple<(T1, T2)>
             public (T1, T2) Pair { get; set; }
         }
 
-        [Fact]
+        [ConditionalFact]
         public async Task OpenGenericDerivedType_AmbiguousInterfaceMatch_ThrowsInvalidOperationException()
         {
+            if (Serializer.IsSourceGeneratedSerializer)
+            {
+                throw new SkipTestException("Source generator rejects this invalid polymorphic configuration at build time (SYSLIB diagnostic); the runtime InvalidOperationException is validated under reflection only.");
+            }
+
             // Impl<T> : IBase<T>, IBase<List<T>> registered on IBase<List<int>>.
             // Both ancestors unify (T=List<int> via the first interface, T=int via the second).
             // Result: ambiguous, throws.
@@ -3189,9 +3224,14 @@ public interface IOpenGenericBase_Ambiguous<T>;
 
         public class OpenGenericImpl_Ambiguous<T> : IOpenGenericBase_Ambiguous<T>, IOpenGenericBase_Ambiguous<List<T>>;
 
-        [Fact]
+        [ConditionalFact]
         public async Task OpenGenericDerivedType_UnboundParameter_ThrowsInvalidOperationException()
         {
+            if (Serializer.IsSourceGeneratedSerializer)
+            {
+                throw new SkipTestException("Source generator rejects this invalid polymorphic configuration at build time (SYSLIB diagnostic); the runtime InvalidOperationException is validated under reflection only.");
+            }
+
             // Derived<T1, T2> : Base<T1> — T2 is unspeakable (not bound by the base type's args).
             var value = new OpenGenericBase_Unbound<int>();
             await Assert.ThrowsAsync<InvalidOperationException>(() => Serializer.SerializeWrapper(value));
@@ -3202,9 +3242,14 @@ public class OpenGenericBase_Unbound<T>;
 
         public class OpenGenericDerived_Unbound<T1, T2> : OpenGenericBase_Unbound<T1>;
 
-        [Fact]
+        [ConditionalFact]
         public async Task OpenGenericDerivedType_ConstraintViolation_ThrowsInvalidOperationException()
         {
+            if (Serializer.IsSourceGeneratedSerializer)
+            {
+                throw new SkipTestException("Source generator rejects this invalid polymorphic configuration at build time (SYSLIB diagnostic); the runtime InvalidOperationException is validated under reflection only.");
+            }
+
             // Derived<T> : Base<T> where T : struct, registered on Base<string>.
             // Constraint fails → InvalidOperationException.
             var value = new OpenGenericBase_StructConstraint<string>();
@@ -3242,6 +3287,8 @@ public async Task OpenGenericDerivedType_DuplicateClosedAndOpenRegistration_Thro
             // Derived<> registration. The open form closes to Derived<int>, producing a
             // duplicate derived-type registration. The existing dup-detection in
             // PolymorphicTypeResolver must surface this as InvalidOperationException.
+            // (Source generator accepts the configuration without warning; the runtime resolver
+            // catches the duplicate, so this scenario validates the same runtime path under both engines.)
             OpenGenericBase_DuplicateDerivedRegistrations<int> value = new OpenGenericDerived_DuplicateDerivedRegistrations<int>();
             await Assert.ThrowsAsync<InvalidOperationException>(() => Serializer.SerializeWrapper(value));
         }
@@ -3491,9 +3538,14 @@ public async Task Variance_BivariantInterface_BothViaVariance_DefaultThrows()
         // behavior. The reflection side has always handled these cases correctly because
         // Type.GetGenericArguments() returns enclosing+leaf args together.
 
-        [Fact]
+        [ConditionalFact]
         public async Task NestedGeneric_EnclosingMismatch_ThrowsInvalidOperationException()
         {
+            if (Serializer.IsSourceGeneratedSerializer)
+            {
+                throw new SkipTestException("Source generator rejects this invalid polymorphic configuration at build time (SYSLIB diagnostic); the runtime InvalidOperationException is validated under reflection only.");
+            }
+
             // Pattern: NestedDerivedEnclosingMismatch<T> : NestedBase<NestedOuter<int>.NestedBox<T>>.
             // Target: NestedBase<NestedOuter<string>.NestedBox<int>>.
             // The enclosing argument differs (int vs string) so unification MUST fail. The
@@ -3788,9 +3840,10 @@ public bool Equals(TBaseType? left, TBaseType? right)
             public int GetHashCode(TBaseType _) => throw new NotImplementedException();
         }
 
-        public class CustomPolymorphismResolver : DefaultJsonTypeInfoResolver
+        public class CustomPolymorphismResolver : IJsonTypeInfoResolver
         {
-            private List<JsonDerivedType> _jsonDerivedTypes = new();
+            private readonly DefaultJsonTypeInfoResolver _inner = new();
+            private readonly List<JsonDerivedType> _jsonDerivedTypes = new();
 
             public CustomPolymorphismResolver(Type baseType)
             {
@@ -3808,10 +3861,10 @@ public CustomPolymorphismResolver WithDerivedType(JsonDerivedType jsonDerivedTyp
                 return this;
             }
 
-            public override JsonTypeInfo GetTypeInfo(Type type, JsonSerializerOptions options)
+            public JsonTypeInfo? GetTypeInfo(Type type, JsonSerializerOptions options)
             {
-                JsonTypeInfo jsonTypeInfo = base.GetTypeInfo(type, options);
-                if (jsonTypeInfo.Type == BaseType)
+                JsonTypeInfo? jsonTypeInfo = _inner.GetTypeInfo(type, options);
+                if (jsonTypeInfo is not null && jsonTypeInfo.Type == BaseType)
                 {
                     jsonTypeInfo.PolymorphismOptions = new()
                     {