Container fixes for the Json Serialization

These changes fix the following:
- Containers treat new values as new objects and make sure they're initialized.
- Fixed sized containers behave slightly different and will initialize all values when a new fixed sized container is created.
- Loading any values to a container will now return PartialDefaults instead of defaults used as adding any value to a container no longer makes the container a default as the default is always an empty container.
- The previous doesn't apply to fixed sized containers as those containers are always considered to have the exact number of values they can hold.

Code/Framework/AzCore/AzCore/Serialization/Json/ArraySerializer.cpp

@@ -32,13 +32,24 @@ namespace AZ
         switch (inputValue.GetType())
         {
         case rapidjson::kArrayType:
-            return LoadContainer(outputValue, outputValueTypeId, inputValue, context);
+            return LoadContainer(outputValue, outputValueTypeId, inputValue, false, context);
 
-        case rapidjson::kObjectType: // fall through
-        case rapidjson::kNullType: // fall through
-        case rapidjson::kStringType: // fall through
-        case rapidjson::kFalseType: // fall through
-        case rapidjson::kTrueType: // fall through
+        case rapidjson::kObjectType:
+            if (IsExplicitDefault(inputValue))
+            {
+                // Because this serializer has only the operation flag "InitializeNewInstance" set, the only time this will be called with
+                // an explicit default is when a new instance has been created.
+                return LoadContainer(outputValue, outputValueTypeId, inputValue, true, context);
+            }
+            [[fallthrough]];
+        case rapidjson::kNullType:
+            [[fallthrough]];
+        case rapidjson::kStringType:
+            [[fallthrough]];
+        case rapidjson::kFalseType:
+            [[fallthrough]];
+        case rapidjson::kTrueType:
+            [[fallthrough]];
         case rapidjson::kNumberType:
             return context.Report(JSR::Tasks::ReadField, JSR::Outcomes::Unsupported,
                 "Unsupported type. AZStd::array entries can only be read from an array.");
@@ -129,7 +140,16 @@ namespace AZ
         }
     }
 
-    JsonSerializationResult::Result JsonArraySerializer::LoadContainer(void* outputValue, const Uuid& outputValueTypeId, const rapidjson::Value& inputValue,
+    auto JsonArraySerializer::GetOperationsFlags() const -> OperationFlags
+    {
+        return OperationFlags::InitializeNewInstance;
+    }
+
+    JsonSerializationResult::Result JsonArraySerializer::LoadContainer(
+        void* outputValue,
+        const Uuid& outputValueTypeId,
+        const rapidjson::Value& inputValue,
+        bool isNewInstance,
         JsonDeserializerContext& context)
     {
         namespace JSR = JsonSerializationResult; // Used to remove name conflicts in AzCore in uber builds.
@@ -154,14 +174,7 @@ namespace AZ
                 "Unable to retrieve the correct container information for AZStd::array instance.");
         }
 
-        const size_t size = container->Size(outputValue);
-        if (inputValue.Size() < size)
-        {
-            return context.Report(JSR::Tasks::ReadField, JSR::Outcomes::Unsupported,
-                "Not enough entries in JSON array to load an AZStd::array from.");
-        }
-
-        ContinuationFlags flags = ContinuationFlags::None;
+        ContinuationFlags flags = isNewInstance ? ContinuationFlags::LoadAsNewInstance : ContinuationFlags::None;
         Uuid elementTypeId = Uuid::CreateNull();
         auto typeEnumCallback = [&elementTypeId, &flags](const Uuid&, const SerializeContext::ClassElement* genericClassElement)
         {
@@ -175,13 +188,23 @@ namespace AZ
         };
         container->EnumTypes(typeEnumCallback);
 
+        const size_t size = container->Size(outputValue);
+        if (!isNewInstance && inputValue.Size() < size)
+        {
+            return context.Report(
+                JSR::Tasks::ReadField, JSR::Outcomes::Unsupported, "Not enough entries in JSON array to load an AZStd::array from.");
+        }
+
+        rapidjson::Value explicitDefaultValue = GetExplicitDefault();
+        
         JSR::ResultCode retVal(JSR::Tasks::ReadField);
         for (size_t i = 0; i < size; ++i)
         {
             ScopedContextPath subPath(context, i);
 
             void* element = container->GetElementByIndex(outputValue, nullptr, i);
-            JSR::ResultCode result = ContinueLoading(element, elementTypeId, inputValue[aznumeric_caster(i)], context, flags);
+            JSR::ResultCode result = ContinueLoading(
+                element, elementTypeId, isNewInstance ? explicitDefaultValue : inputValue[aznumeric_caster(i)], context, flags);
             if (result.GetProcessing() == JSR::Processing::Halted)
             {
                 return context.Report(result, "Failed to load data to element in AZStd::array.");
@@ -189,15 +212,19 @@ namespace AZ
             retVal.Combine(result);
         }
 
-        if (container->Size(outputValue) == inputValue.Size())
+        if (isNewInstance)
+        {
+            return context.Report(retVal, "Filled new instance of AZStd::array with defaults.");
+        }
+        else if (container->Size(outputValue) == inputValue.Size())
         {
             return context.Report(retVal, "Successfully read entries into AZStd::array.");
         }
         else
         {
             retVal.Combine(JSR::ResultCode(JSR::Tasks::ReadField, JSR::Outcomes::Skipped));
-            return context.Report(retVal,
-                "Successfully read available entries into AZStd::array, but there were still values left in the JSON array.");
+            return context.Report(
+                retVal, "Successfully read available entries into AZStd::array, but there were still values left in the JSON array.");
         }
     }
 } // namespace AZ

Code/Framework/AzCore/AzCore/Serialization/Json/ArraySerializer.h

@@ -30,8 +30,14 @@ namespace AZ
         JsonSerializationResult::Result Store(rapidjson::Value& outputValue, const void* inputValue, const void* defaultValue,
             const Uuid& valueTypeId, JsonSerializerContext& context) override;
 
+        OperationFlags GetOperationsFlags() const override;
+
     protected:
-        JsonSerializationResult::Result LoadContainer(void* outputValue, const Uuid& outputValueTypeId, const rapidjson::Value& inputValue,
+        JsonSerializationResult::Result LoadContainer(
+            void* outputValue,
+            const Uuid& outputValueTypeId,
+            const rapidjson::Value& inputValue,
+            bool isNewInstance,
             JsonDeserializerContext& context);
     };
 } // namespace AZ

Code/Framework/AzCore/AzCore/Serialization/Json/BasicContainerSerializer.cpp

@@ -34,11 +34,16 @@ namespace AZ
         case rapidjson::kArrayType:
             return LoadContainer(outputValue, outputValueTypeId, inputValue, context);
 
-        case rapidjson::kObjectType: // fall through
-        case rapidjson::kNullType: // fall through
-        case rapidjson::kStringType: // fall through
-        case rapidjson::kFalseType: // fall through
-        case rapidjson::kTrueType: // fall through
+        case rapidjson::kObjectType:
+            [[fallthrough]];
+        case rapidjson::kNullType:
+            [[fallthrough]];
+        case rapidjson::kStringType:
+            [[fallthrough]];
+        case rapidjson::kFalseType:
+            [[fallthrough]];
+        case rapidjson::kTrueType:
+            [[fallthrough]];
         case rapidjson::kNumberType:
             return context.Report(JSR::Tasks::ReadField, JSR::Outcomes::Unsupported,
                 "Unsupported type. Basic containers can only be read from an array.");
@@ -169,6 +174,7 @@ namespace AZ
         ContinuationFlags flags = classElement->m_flags & SerializeContext::ClassElement::Flags::FLG_POINTER
             ? ContinuationFlags::ResolvePointer
             : ContinuationFlags::None;
+        flags |= ContinuationFlags::LoadAsNewInstance;
 
         const size_t capacity = container->IsFixedCapacity() ? container->Capacity(outputValue) : std::numeric_limits<size_t>::max();
 
@@ -247,6 +253,11 @@ namespace AZ
         }
 
         size_t addedCount = container->Size(outputValue) - containerSize;
+        if (addedCount > 0)
+        {
+            // Values were added which means the container is no longer in its default state of being emtpy.
+            retVal.Combine(JSR::ResultCode(JSR::Tasks::ReadField, JSR::Outcomes::Success));
+        }
         AZStd::string_view message =
             addedCount >= arraySize ? "Successfully read basic container.":
             addedCount == 0 ? "Unable to read data for basic container." :

Code/Framework/AzCore/AzCore/Serialization/Json/MapSerializer.cpp

@@ -190,6 +190,12 @@ namespace AZ
         }
 
         size_t addedCount = container->Size(outputValue) - containerSize;
+        if (addedCount > 0)
+        {
+            // If at least one entry was added then the map is no longer in it's default state so
+            // mark is with success so the result can at best be partial defaults.
+            retVal.Combine(JSR::ResultCode(JSR::Tasks::ReadField, JSR::Outcomes::Success));
+        }
         AZStd::string_view message =
             addedCount >= maximumSize ? "Successfully read associative container." :
             addedCount == 0 ? "Unable to read data for the associative container." : 
@@ -215,10 +221,10 @@ namespace AZ
         // Load key
         void* keyAddress = pairContainer->GetElementByIndex(address, pairElement, 0);
         AZ_Assert(keyAddress, "Element reserved for associative container, but unable to retrieve address of the key.");
-        ContinuationFlags keyLoadFlags = ContinuationFlags::None;
+        ContinuationFlags keyLoadFlags = ContinuationFlags::LoadAsNewInstance;
         if (keyElement->m_flags & SerializeContext::ClassElement::Flags::FLG_POINTER)
         {
-            keyLoadFlags = ContinuationFlags::ResolvePointer;
+            keyLoadFlags |= ContinuationFlags::ResolvePointer;
             *reinterpret_cast<void**>(keyAddress) = nullptr;
         }
         JSR::ResultCode keyResult = ContinueLoading(keyAddress, keyElement->m_typeId, key, context, keyLoadFlags);
@@ -231,10 +237,10 @@ namespace AZ
         // Load value
         void* valueAddress = pairContainer->GetElementByIndex(address, pairElement, 1);
         AZ_Assert(valueAddress, "Element reserved for associative container, but unable to retrieve address of the value.");
-        ContinuationFlags valueLoadFlags = ContinuationFlags::None; 
+        ContinuationFlags valueLoadFlags = ContinuationFlags::LoadAsNewInstance; 
         if (valueElement->m_flags & SerializeContext::ClassElement::Flags::FLG_POINTER)
         {
-            valueLoadFlags = ContinuationFlags::ResolvePointer;
+            valueLoadFlags |= ContinuationFlags::ResolvePointer;
             *reinterpret_cast<void**>(valueAddress) = nullptr;
         }
         JSR::ResultCode valueResult = ContinueLoading(valueAddress, valueElement->m_typeId, value, context, valueLoadFlags);

Code/Framework/AzCore/AzCore/Serialization/Json/TupleSerializer.cpp

@@ -34,13 +34,24 @@ namespace AZ
         switch (inputValue.GetType())
         {
         case rapidjson::kArrayType:
-            return LoadContainer(outputValue, outputValueTypeId, inputValue, context);
+            return LoadContainer(outputValue, outputValueTypeId, inputValue, false, context);
         
-        case rapidjson::kObjectType: // fall through
-        case rapidjson::kNullType: // fall through
-        case rapidjson::kStringType: // fall through
-        case rapidjson::kFalseType: // fall through
-        case rapidjson::kTrueType: // fall through
+        case rapidjson::kObjectType:
+            if (IsExplicitDefault(inputValue))
+            {
+                // Because this serializer has only the operation flag "InitializeNewInstance" set, the only time this will be called with
+                // an explicit default is when a new instance has been created.
+                return LoadContainer(outputValue, outputValueTypeId, inputValue, true, context);
+            }
+            [[fallthrough]];
+        case rapidjson::kNullType:
+            [[fallthrough]];
+        case rapidjson::kStringType:
+            [[fallthrough]];
+        case rapidjson::kFalseType:
+            [[fallthrough]];
+        case rapidjson::kTrueType:
+            [[fallthrough]];
         case rapidjson::kNumberType:
             return context.Report(JSR::Tasks::ReadField, JSR::Outcomes::Unsupported,
                 "Unsupported type. AZStd::pair or AZStd::tuple can only be read from an array.");
@@ -127,8 +138,13 @@ namespace AZ
         }
     }
 
+    auto JsonTupleSerializer::GetOperationsFlags() const -> OperationFlags
+    {
+        return OperationFlags::InitializeNewInstance;
+    }
+
     JsonSerializationResult::Result JsonTupleSerializer::LoadContainer(void* outputValue, const Uuid& outputValueTypeId,
-        const rapidjson::Value& inputValue, JsonDeserializerContext& context)
+        const rapidjson::Value& inputValue, bool isNewInstance, JsonDeserializerContext& context)
     {
         namespace JSR = JsonSerializationResult; // Used to remove name conflicts in AzCore in uber builds.
 
@@ -154,7 +170,7 @@ namespace AZ
         };
         container->EnumTypes(typeCountCallback);
 
-        rapidjson::SizeType arraySize = inputValue.Size();
+        rapidjson::SizeType arraySize = isNewInstance ? typeCount : inputValue.Size();
         if (arraySize < typeCount)
         {
             return context.Report(JSR::Tasks::ReadField, JSR::Outcomes::Unsupported,
@@ -171,46 +187,73 @@ namespace AZ
         container->EnumTypes(typeEnumCallback);
 
         JSR::ResultCode retVal(JSR::Tasks::ReadField);
-        rapidjson::SizeType arrayIndex = 0;
-        size_t numElementsWritten = 0;
-        for (size_t i = 0; i < typeCount; ++i)
+        if (isNewInstance)
         {
-            ScopedContextPath subPath(context, i);
-            
-            void* elementAddress = container->GetElementByIndex(outputValue, nullptr, i);
-            AZ_Assert(elementAddress, "Address of AZStd::pair or AZStd::tuple element %zu could not be retrieved.", i);
+            rapidjson::Value explicitDefaultValue = GetExplicitDefault();
 
-            ContinuationFlags flags = classElements[i]->m_flags & SerializeContext::ClassElement::Flags::FLG_POINTER
-                ? ContinuationFlags::ResolvePointer
-                : ContinuationFlags::None;
-
-            while (arrayIndex < inputValue.Size())
+            for (size_t i = 0; i < typeCount; ++i)
             {
-                JSR::ResultCode result = ContinueLoading(elementAddress, classElements[i]->m_typeId, inputValue[arrayIndex], context, flags);
+                ScopedContextPath subPath(context, i);
+
+                void* elementAddress = container->GetElementByIndex(outputValue, nullptr, i);
+                AZ_Assert(elementAddress, "Address of AZStd::pair or AZStd::tuple element %zu could not be retrieved.", i);
+
+                ContinuationFlags flags = ContinuationFlags::LoadAsNewInstance;
+                flags |=
+                    (classElements[i]->m_flags & SerializeContext::ClassElement::Flags::FLG_POINTER ? ContinuationFlags::ResolvePointer
+                                                                                                    : ContinuationFlags::None);
+                JSR::ResultCode result = ContinueLoading(elementAddress, classElements[i]->m_typeId, explicitDefaultValue, context, flags);
                 retVal.Combine(result);
-                arrayIndex++;
                 if (result.GetProcessing() == JSR::Processing::Halted)
                 {
                     return context.Report(retVal, "Failed to read element for AZStd::pair or AZStd::tuple.");
                 }
-                else if (result.GetProcessing() != JSR::Processing::Altered)
-                {
-                    numElementsWritten++;
-                    break;
-                }
             }
-        }
 
-        if (numElementsWritten < typeCount)
-        {
-            AZStd::string_view message = numElementsWritten == 0 ?
-                "Unable to read data for AZStd::pair or AZStd::tuple." :
-                "Partially read data for AZStd::pair or AZStd::tuple.";
-            return context.Report(retVal, message);
+            return context.Report(retVal, "Initialized AZStd::pair or AZStd::tuple to defaults.");
         }
         else
         {
-            return context.Report(retVal, "Successfully read AZStd::pair or AZStd::tuple.");
+            rapidjson::SizeType arrayIndex = 0;
+            size_t numElementsWritten = 0;
+            for (size_t i = 0; i < typeCount; ++i)
+            {
+                ScopedContextPath subPath(context, i);
+
+                void* elementAddress = container->GetElementByIndex(outputValue, nullptr, i);
+                AZ_Assert(elementAddress, "Address of AZStd::pair or AZStd::tuple element %zu could not be retrieved.", i);
+
+                ContinuationFlags flags =
+                    (classElements[i]->m_flags & SerializeContext::ClassElement::Flags::FLG_POINTER ? ContinuationFlags::ResolvePointer
+                                                                                                    : ContinuationFlags::None);
+                while (arrayIndex < inputValue.Size())
+                {
+                    JSR::ResultCode result =
+                        ContinueLoading(elementAddress, classElements[i]->m_typeId, inputValue[arrayIndex], context, flags);
+                    retVal.Combine(result);
+                    arrayIndex++;
+                    if (result.GetProcessing() == JSR::Processing::Halted)
+                    {
+                        return context.Report(retVal, "Failed to read element for AZStd::pair or AZStd::tuple.");
+                    }
+                    else if (result.GetProcessing() != JSR::Processing::Altered)
+                    {
+                        numElementsWritten++;
+                        break;
+                    }
+                }
+            }
+
+            if (numElementsWritten < typeCount)
+            {
+                AZStd::string_view message = numElementsWritten == 0 ? "Unable to read data for AZStd::pair or AZStd::tuple."
+                                                                     : "Partially read data for AZStd::pair or AZStd::tuple.";
+                return context.Report(retVal, message);
+            }
+            else
+            {
+                return context.Report(retVal, "Successfully read AZStd::pair or AZStd::tuple.");
+            }
         }
     }
 } // namespace AZ

Code/Framework/AzCore/AzCore/Serialization/Json/TupleSerializer.h

@@ -23,13 +23,20 @@ namespace AZ
     public:
         AZ_RTTI(JsonTupleSerializer, "{1AA0ADC1-395A-4223-8A73-304ACDEE7793}", BaseJsonSerializer);
         AZ_CLASS_ALLOCATOR_DECL;
+
         JsonSerializationResult::Result Load(void* outputValue, const Uuid& outputValueTypeId, const rapidjson::Value& inputValue,
             JsonDeserializerContext& context) override;
         JsonSerializationResult::Result Store(rapidjson::Value& outputValue, const void* inputValue, const void* defaultValue,
             const Uuid& valueTypeId, JsonSerializerContext& context) override;
 
+        OperationFlags GetOperationsFlags() const override;
+
     private:
-        JsonSerializationResult::Result LoadContainer(void* outputValue, const Uuid& outputValueTypeId, const rapidjson::Value& inputValue,
+        JsonSerializationResult::Result LoadContainer(
+            void* outputValue,
+            const Uuid& outputValueTypeId,
+            const rapidjson::Value& inputValue,
+            bool isNewInstance,
             JsonDeserializerContext& context);
     };
 } // namespace AZ