Can't use C# 9.0 Record for actor method return type

[LukePammant]

Expected Behavior

I would like to use a record as a return type for an actor method.

Actual Behavior

ActorInvokeException: Type 'Chronos.Actors.EquipmentAssignments' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. Alternatively, you can ensure that the type is public and has a parameterless constructor - all public members of the type will then be serialized, and no attributes will be required.

Here is the record definition:

    public record EquipmentActorState(Guid Id, Guid SolarSystemId, string OwnerTypeId, EquipmentAssignments EquipmentAssignments, List<EquipmentSwapRequest> SwapRequests);
    public record EquipmentAssignments(Guid Id, string ShipTypeId, Dictionary<int, EquipmentSlot> EquipmentSlots, Dictionary<Guid, EquipmentReference> AvailableEquipment);
    public record EquipmentSlot(EquipmentSlotType Type, Guid? CurrentlyAssignedEquipment);
    public record EquipmentReference(Guid Id, string Type, EquipmentSlotType SlotType, int? AssignedSlotId);

//... Inside the actor class definition
    public async Task<EquipmentAssignments?> GetEquipmentDetails()
    {
         var state = await StateManager.GetStateAsync<EquipmentActorState>("state");
         return state.EquipmentAssignments; // <-- this cannot be serialized?
    }

It fails on this line in the dotnet-sdk:
https://github.com/dapr/dotnet-sdk/blob/master/src/Dapr.Actors/Communication/ActorMessageBodyDataContractSerializationProvider.cs#L206

Which throws this exception:

Exception has occurred: CLR/System.Runtime.Serialization.InvalidDataContractException
Exception thrown: 'System.Runtime.Serialization.InvalidDataContractException' in System.Private.DataContractSerialization.dll: 'Type 'Chronos.Actors.EquipmentAssignments' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. Alternatively, you can ensure that the type is public and has a parameterless constructor - all public members of the type will then be serialized, and no attributes will be required.'
   at System.Runtime.Serialization.DataContract.DataContractCriticalHelper.ThrowInvalidDataContractException(String message, Type type)
   at System.Runtime.Serialization.DataContract.DataContractCriticalHelper.CreateDataContract(Type type)
   at System.Runtime.Serialization.DataContract.DataContractCriticalHelper.CreateDataContract(Int32 id, RuntimeTypeHandle typeHandle, Type type)
   at System.Runtime.Serialization.DataContract.DataContractCriticalHelper.GetDataContractSkipValidation(Int32 id, RuntimeTypeHandle typeHandle, Type type)
   at System.Runtime.Serialization.DataContract.GetDataContract(RuntimeTypeHandle typeHandle, Type type, SerializationMode mode)
   at System.Runtime.Serialization.XmlObjectSerializerContext.GetDataContract(RuntimeTypeHandle typeHandle, Type type)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContextComplex.InternalSerializeWithSurrogate(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContextComplex.InternalSerialize(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.InternalSerializeReference(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.ClassDataContract.WriteXmlValue(XmlWriterDelegator xmlWriter, Object obj, XmlObjectSerializerWriteContext context)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.WriteDataContractValue(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeAndVerifyType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, Boolean verifyKnownType, RuntimeTypeHandle declaredTypeHandle, Type declaredType)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithXsiType(XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle objectTypeHandle, Type objectType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle, Type declaredType)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContextComplex.InternalSerializeWithSurrogate(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContextComplex.InternalSerialize(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.InternalSerializeReference(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.ClassDataContract.WriteXmlValue(XmlWriterDelegator xmlWriter, Object obj, XmlObjectSerializerWriteContext context)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.WriteDataContractValue(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithoutXsiType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.DataContractSerializer.InternalWriteObjectContent(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.DataContractSerializer.InternalWriteObject(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.XmlObjectSerializer.WriteObjectHandleExceptions(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.XmlObjectSerializer.WriteObject(XmlDictionaryWriter writer, Object graph)
   at Dapr.Actors.Communication.ActorMessageBodyDataContractSerializationProvider.MemoryStreamMessageBodySerializer`2.Dapr.Actors.Communication.IActorResponseMessageBodySerializer.Serialize(IActorResponseMessageBody actorResponseMessageBody) in /dotnet-sdk/src/Dapr.Actors/Communication/ActorMessageBodyDataContractSerializationProvider.cs:line 206

Steps to Reproduce the Problem

Return a Record type from an actor and call it using the dotnet-sdk

Release Note

RELEASE NOTE:

[rynowak]

I agree that this would be nice to enable, but it's not something we can easily do within the .NET SDK unless we make more options available for choosing the serializer. .NET Actors use DataContractSerializer when used with strongly-typed contracts, and so we have all of its limitations and properties.

[LukePammant]

Okay, that makes sense. Would it be worth me looking into using something like System.Text.Json in the Actors? It looks like it's being used for the state persistence.

[rynowak]

I think it be worth starting a design discussion of what it would mean to make the serializer pluggable for actors. #476

As with all things we need to provide a graceful migration path and avoid changing things in a big-bang.

For instance. If you could attribute an interface in a way that configured the serializer. This allows client and server to change together, and would allow migrating apps per-interfacer/per-actor.

Also complicating this is that DataContractSerializer is pretty feature-rich, and not everything it does will be supported in other serializers. Eg. cycle handling, knowntypes. Realistically we will need to keep DCS support forever. Most users don't intimately understand what the serializer is doing, they just have working code, and they would be unhappy if we turn it into non-working code in a version upgrade.

[onionhammer]

Bumping.. cant seem to use them for arguments either. Easily system.text.json serializable stuff just doesnt work with whatever voodoo ActorMessageBodyDataContractSerializationProvider is doing... just stop doing voodoo and voila, things will work better.

Why provide ActorProxyOptions.JsonSerializerOptions? What is that for? Is it ignored?

[paulyuk]

@halspang @johnewart, thoughts? I hit this too immediately building Actor quickstart.

[onionhammer]

@halspang is there a tracking issue for custom serialization support for Dapr actor remoting functions? I'm seeing a lot of beating around the bush, but the clear culprit for a lot of issues is the use of the DataContractSerializer, and that it is not able to be configured or replaced

Maybe #476 but it's only tangentially related and old