Fix DataContractJsonSerializer not passing ISerializationSurrogateProvider to internal serializer (#118257)

- [x] Initial plan
- [x] Fix DataContractJsonSerializer to pass
ISerializationSurrogateProvider to internal serializer contexts
- [x] Complete fix for DataContractJsonSerializer surrogate provider
support
- [x] Address PR review feedback:
- Replace custom test classes with shared
NonSerializablePerson/MyPersonSurrogateProvider from
SerializationTypes.RuntimeOnly.cs
- Use consistent single-line pattern for RootContract property matching
DataContractSerializer
- Remove unnecessary cache invalidation logic that sets _rootContract =
null
- Add *WasCalled properties to MyPersonSurrogateProvider for test
validation

## Summary

Successfully implemented and refined DataContractJsonSerializer
surrogate provider support:

1. **Core Fix**: Added new constructors to
XmlObjectSerializerReadContextComplexJson and
XmlObjectSerializerWriteContextComplexJson that properly pass the
ISerializationSurrogateProvider to base classes
2. **Contract Resolution**: Fixed RootContract property to call
GetSurrogatedType when surrogate provider is present
3. **Code Quality**: Addressed all review feedback to improve
consistency and reuse existing test infrastructure
4. **Validation**: All tests pass, confirming surrogate provider methods
are properly called during JSON serialization/deserialization

The fix ensures DataContractJsonSerializer now properly respects
SetSerializationSurrogateProvider() calls, matching the behavior of
DataContractSerializer.

Fixes: #100553

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: StephenMolloy <19562826+StephenMolloy@users.noreply.github.com>
Co-authored-by: Steve Molloy <smolloy@microsoft.com>

Author: Copilot

src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/Json/DataContractJsonSerializer.cs

@@ -188,7 +188,7 @@ private DataContract RootContract
             {
                 if (_rootContract == null)
                 {
-                    _rootContract = DataContract.GetDataContract(_rootType);
+                    _rootContract = DataContract.GetDataContract((_serializationSurrogateProvider == null) ? _rootType : GetSurrogatedType(_serializationSurrogateProvider, _rootType));
                     CheckIfTypeIsReference(_rootContract);
                 }
                 return _rootContract;
@@ -654,5 +654,12 @@ internal static DataContract GetDataContract(DataContract declaredTypeContract,
             CheckIfTypeIsReference(contract);
             return contract;
         }
+
+        [RequiresDynamicCode(DataContract.SerializerAOTWarning)]
+        [RequiresUnreferencedCode(DataContract.SerializerTrimmerWarning)]
+        internal static Type GetSurrogatedType(ISerializationSurrogateProvider serializationSurrogateProvider, Type type)
+        {
+            return DataContractSurrogateCaller.GetDataContractType(serializationSurrogateProvider, DataContract.UnwrapNullableType(type));
+        }
     }
 }

src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/Json/XmlObjectSerializerReadContextComplexJson.cs

@@ -20,7 +20,7 @@ internal sealed class XmlObjectSerializerReadContextComplexJson : XmlObjectSeria
 
         internal XmlObjectSerializerReadContextComplexJson(DataContractJsonSerializer serializer, DataContract rootTypeDataContract)
 #pragma warning disable SYSLIB0050 // StreamingContext ctor is obsolete
-            : base(serializer, serializer.MaxItemsInObjectGraph, new StreamingContext(StreamingContextStates.All), serializer.IgnoreExtensionDataObject)
+            : base(serializer, serializer.MaxItemsInObjectGraph, new StreamingContext(StreamingContextStates.All), serializer.IgnoreExtensionDataObject, serializer.SerializationSurrogateProvider)
 #pragma warning restore SYSLIB0050
         {
             this.rootTypeDataContract = rootTypeDataContract;

src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/Json/XmlObjectSerializerWriteContextComplexJson.cs

@@ -26,7 +26,7 @@ internal static XmlObjectSerializerWriteContextComplexJson CreateContext(DataCon
 
         internal XmlObjectSerializerWriteContextComplexJson(DataContractJsonSerializer serializer, DataContract rootTypeDataContract)
 #pragma warning disable SYSLIB0050 // StreamingContext ctor is obsolete
-            : base(serializer, serializer.MaxItemsInObjectGraph, new StreamingContext(StreamingContextStates.All), serializer.IgnoreExtensionDataObject)
+            : base(serializer, serializer.MaxItemsInObjectGraph, new StreamingContext(StreamingContextStates.All), serializer.IgnoreExtensionDataObject, serializer.SerializationSurrogateProvider)
 #pragma warning restore SYSLIB0050
         {
             _emitXsiType = serializer.EmitTypeInformation;

src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/XmlObjectSerializerReadContextComplex.cs

@@ -26,6 +26,12 @@ internal XmlObjectSerializerReadContextComplex(XmlObjectSerializer serializer, i
         {
         }
 
+        internal XmlObjectSerializerReadContextComplex(XmlObjectSerializer serializer, int maxItemsInObjectGraph, StreamingContext streamingContext, bool ignoreExtensionDataObject, ISerializationSurrogateProvider? serializationSurrogateProvider)
+            : base(serializer, maxItemsInObjectGraph, streamingContext, ignoreExtensionDataObject)
+        {
+            _serializationSurrogateProvider = serializationSurrogateProvider;
+        }
+
         [RequiresDynamicCode(DataContract.SerializerAOTWarning)]
         [RequiresUnreferencedCode(DataContract.SerializerTrimmerWarning)]
         internal override object? InternalDeserialize(XmlReaderDelegator xmlReader, int declaredTypeID, RuntimeTypeHandle declaredTypeHandle, string name, string ns)

src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/XmlObjectSerializerWriteContextComplex.cs

@@ -33,6 +33,12 @@ internal XmlObjectSerializerWriteContextComplex(XmlObjectSerializer serializer,
         {
         }
 
+        internal XmlObjectSerializerWriteContextComplex(XmlObjectSerializer serializer, int maxItemsInObjectGraph, StreamingContext streamingContext, bool ignoreExtensionDataObject, ISerializationSurrogateProvider? serializationSurrogateProvider)
+            : base(serializer, maxItemsInObjectGraph, streamingContext, ignoreExtensionDataObject)
+        {
+            _serializationSurrogateProvider = serializationSurrogateProvider;
+        }
+
         internal override bool WriteClrTypeInfo(XmlWriterDelegator xmlWriter, DataContract dataContract)
         {
             return false;

src/libraries/System.Runtime.Serialization.Json/tests/DataContractJsonSerializer.cs

@@ -3123,4 +3123,69 @@ private static string GetAmString(DateTimeFormat dateTimeFormat)
     {
         return ((CultureInfo)dateTimeFormat.FormatProvider).DateTimeFormat.AMDesignator;
     }
+
+    // Test for the fix to ensure DataContractJsonSerializer passes ISerializationSurrogateProvider to internal XML serializer
+    // Same tests used for the regular DataContractSerializer to ensure the surrogate provider is working correctly
+    [Fact]
+    public static void DCJS_MyPersonSurrogate()
+    {
+        DataContractJsonSerializer dcjs = new DataContractJsonSerializer(typeof(Family));
+        dcjs.SetSerializationSurrogateProvider(new MyPersonSurrogateProvider());
+        MemoryStream ms = new MemoryStream();
+        Family myFamily = new Family
+        {
+            Members = new NonSerializablePerson[]
+            {
+                new NonSerializablePerson("John", 34),
+                new NonSerializablePerson("Jane", 32),
+                new NonSerializablePerson("Bob", 5),
+            }
+        };
+        dcjs.WriteObject(ms, myFamily);
+        ms.Position = 0;
+        var newFamily = (Family)dcjs.ReadObject(ms);
+        Assert.Equal(myFamily.Members.Length, newFamily.Members.Length);
+        for (int i = 0; i < myFamily.Members.Length; ++i)
+        {
+            Assert.Equal(myFamily.Members[i].Name, newFamily.Members[i].Name);
+            Assert.Equal(myFamily.Members[i].Age, newFamily.Members[i].Age);
+        }
+    }
+
+    [Fact]
+    public static void DCJS_FileStreamSurrogate()
+    {
+        using (var testFile = TempFile.Create())
+        {
+            const string TestFileData = "Some data for data contract surrogate test";
+
+            // Create the serializer and specify the surrogate
+            var dcjs = new DataContractJsonSerializer(typeof(MyFileStream));
+            dcjs.SetSerializationSurrogateProvider(MyFileStreamSurrogateProvider.Singleton);
+
+            // Create and initialize the stream
+            byte[] serializedStream;
+
+            // Serialize the stream
+            using (var stream1 = new MyFileStream(testFile.Path))
+            {
+                stream1.WriteLine(TestFileData);
+                using (var memoryStream = new MemoryStream())
+                {
+                    dcjs.WriteObject(memoryStream, stream1);
+                    serializedStream = memoryStream.ToArray();
+                }
+            }
+
+            // Deserialize the stream
+            using (var stream = new MemoryStream(serializedStream))
+            {
+                using (var stream2 = (MyFileStream)dcjs.ReadObject(stream))
+                {
+                    string fileData = stream2.ReadLine();
+                    Assert.Equal(TestFileData, fileData);
+                }
+            }
+        }
+    }
 }

src/libraries/System.Runtime.Serialization.Json/tests/ReflectionOnly/System.Runtime.Serialization.Json.ReflectionOnly.Tests.csproj

@@ -7,10 +7,11 @@
     <EnableAotAnalyzer>false</EnableAotAnalyzer>
   </PropertyGroup>
   <ItemGroup>
-    <Compile Include="$(CommonTestPath)System\Runtime\Serialization\Utils.cs" />
     <Compile Include="$(TestSourceFolder)..\..\..\System.Runtime.Serialization.Xml\tests\SerializationTypes.cs" />
     <Compile Include="$(TestSourceFolder)..\..\..\System.Runtime.Serialization.Xml\tests\SerializationTypes.RuntimeOnly.cs" />
     <Compile Include="$(TestSourceFolder)..\DataContractJsonSerializer.cs" />
+    <Compile Include="$(CommonTestPath)System\IO\TempFile.cs" Link="Common\System\IO\TempFile.cs" />
+    <Compile Include="$(CommonTestPath)System\Runtime\Serialization\Utils.cs" />
 
     <TrimmerRootDescriptor Include="$(ILLinkDescriptorsPath)ILLink.Descriptors.Serialization.xml" />
   </ItemGroup>

src/libraries/System.Runtime.Serialization.Json/tests/System.Runtime.Serialization.Json.Tests.csproj

@@ -9,6 +9,7 @@
     <Compile Include="$(TestSourceFolder)DataContractJsonSerializer.cs" />
     <Compile Include="$(TestSourceFolder)..\..\System.Runtime.Serialization.Xml\tests\SerializationTypes.cs" />
     <Compile Include="$(TestSourceFolder)..\..\System.Runtime.Serialization.Xml\tests\SerializationTypes.RuntimeOnly.cs" />
+    <Compile Include="$(CommonTestPath)System\IO\TempFile.cs" Link="Common\System\IO\TempFile.cs" />
     <Compile Include="$(CommonTestPath)System\Runtime\Serialization\Utils.cs" />
 
     <TrimmerRootDescriptor Include="$(ILLinkDescriptorsPath)ILLink.Descriptors.Serialization.xml" />

src/libraries/System.Runtime.Serialization.Xml/tests/DataContractSerializer.cs

@@ -4216,6 +4216,7 @@ public static void DCS_MyPersonSurrogate()
         for (int i = 0; i < myFamily.Members.Length; ++i)
         {
             Assert.Equal(myFamily.Members[i].Name, newFamily.Members[i].Name);
+            Assert.Equal(myFamily.Members[i].Age, newFamily.Members[i].Age);
         }
     }