[LYN-9039] Object stream write response change (#7085)

* Updated the ObjectStreamWriteOverride Callback to return a
ObjectStreamWriteOverrideResponse.

The ObjectStreamWriteOverrideResponse allows the callback to indicate
that the default ObjectStream::WriteElement behavior should occur if the
callback hasn't implemented the write itself.

Signed-off-by: lumberyard-employee-dm <56135373+lumberyard-employee-dm@users.noreply.github.com>

* Fixed forward declaration not matching actual enum class name

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Add unit tests

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Remove unused member

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Add virtual destructor for test class

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

* Change string literal to not have tabs in it

Signed-off-by: amzn-mike <80125227+amzn-mike@users.noreply.github.com>

Co-authored-by: lumberyard-employee-dm <56135373+lumberyard-employee-dm@users.noreply.github.com>

Code/Framework/AzCore/AzCore/Serialization/ObjectStream.cpp

@@ -1668,9 +1668,23 @@ namespace AZ
                     SerializeContext::ENUM_ACCESS_FOR_READ,
                     &m_errorLogger
                 );
-                if (objectStreamWriteOverrideCB.Invoke<void>(callContext, objectPtr, *classData, classElement))
+                if (ObjectStreamWriteOverrideResponse writeResponse;
+                    objectStreamWriteOverrideCB.Read<ObjectStreamWriteOverrideResponse>(writeResponse, callContext, objectPtr, *classData, classElement))
                 {
-                    return false;
+                    switch (writeResponse)
+                    {
+                    case ObjectStreamWriteOverrideResponse::FallbackToDefaultWrite:
+                        break;
+                    case ObjectStreamWriteOverrideResponse::AbortWrite:
+                        m_errorLogger.ReportError(AZStd::string::format("ObjectStream Write Element Override callback has aborted the write for class data %s",
+                            classData->m_name).c_str());
+                        [[fallthrough]];
+                    case ObjectStreamWriteOverrideResponse::CompletedWrite:
+                        return false;
+                    default:
+                        AZ_Error("Serialize", false, "Invalid Response %d returned from the ObjectStream Write Element Override callback", static_cast<int>(writeResponse));
+                        return false;
+                    }
                 }
                 else
                 {

Code/Framework/AzCore/AzCore/Serialization/ObjectStream.h

@@ -49,14 +49,24 @@ namespace AZ
         static const AZ::Crc32 ObjectStreamWriteElementOverride = AZ_CRC("ObjectStreamWriteElementOverride", 0x35eb659f);
     }
 
+    enum class ObjectStreamWriteOverrideResponse
+    {
+        CompletedWrite,
+        FallbackToDefaultWrite,
+        AbortWrite
+    };
+    AZ_TYPE_INFO_SPECIALIZE(ObjectStreamWriteOverrideResponse, "{BDF960A8-0F18-4E9D-96DA-F800A122C42D}");
+
     ///< Callback that the object stream invokes to override saving an instance of the registered class
     ///< @param callContext EnumerateInstanceCallContext which contains the WriteElement BeingElemCB and the CloseElement EndElemCB
     ///< the callContext parameter can be passed to the SerializeContext::EnumerateInstance to continue object stream writing
     ///< @param classPtr class type which is of pointer to the type represented by the m_typeId value
     ///< @param classData reference to this instance Class Data that will be supplied to the callback
     ///< @param classElement class element pointer which contains information about the element being serialized.
-    ///< root elements do not not have a valid class element pointer
-    using ObjectStreamWriteOverrideCB = AZStd::function<void(SerializeContext::EnumerateInstanceCallContext& callContext,
+    ///<        root elements have a nullptr classElement
+    ///< @return enum to indicate that the override has saved the registered class and that the default writing should be skipped.
+    ///<         Returning false will have the WriteElement code fallback to using the default logic
+    using ObjectStreamWriteOverrideCB = AZStd::function<ObjectStreamWriteOverrideResponse(SerializeContext::EnumerateInstanceCallContext& callContext,
         const void* classPtr, const SerializeContext::ClassData& classData, const SerializeContext::ClassElement* classElement)>;
 
     AZ_TYPE_INFO_SPECIALIZE(ObjectStreamWriteOverrideCB, "{87B1A36B-8C8A-42B6-A0B5-E770D9FDBAD4}");

Code/Framework/AzCore/AzCore/Serialization/std/VariantReflection.inl

@@ -12,6 +12,8 @@
 
 namespace AZ
 {
+    enum class ObjectStreamWriteOverrideResponse;
+
     namespace VariantSerializationInternal
     {
         template <class ValueType>
@@ -480,7 +482,7 @@ namespace AZ
                 }
             }
         private:
-            static void ObjectStreamWriter(SerializeContext::EnumerateInstanceCallContext& callContext, const void* variantPtr,
+            static ObjectStreamWriteOverrideResponse ObjectStreamWriter(SerializeContext::EnumerateInstanceCallContext& callContext, const void* variantPtr,
                 [[maybe_unused]] const SerializeContext::ClassData& variantClassData, const SerializeContext::ClassElement* variantClassElement)
             {
                 auto alternativeVisitor = [&callContext, variantClassElement](auto&& elementAlt)
@@ -503,6 +505,9 @@ namespace AZ
                 };
 
                 AZStd::visit(AZStd::move(alternativeVisitor), *reinterpret_cast<const VariantType*>(variantPtr));
+                // To avoid including ObjectStream.h into this file, we static cast the value of 0
+                // to an AZ::ObjectStreamWriteElemntResponse which corresponds to the CompletedWrite enum value
+                return static_cast<AZ::ObjectStreamWriteOverrideResponse>(0);
             }
 
             VariantSerializationInternal::AZStdVariantContainer<Types...> m_variantContainer;