Private fields on base class do not get serialized

[QsROg8320]

Bug description

Private fields on base class do not get serialized

Repro steps

DerivedFromBase message = new DerivedFromBase();
message.Add(0);

var bytes = MessagePackSerializer.Serialize(message, TypelessContractlessStandardResolver.Options);
var deserialized = MessagePackSerializer.Deserialize<DerivedFromBase>(bytes, TypelessContractlessStandardResolver.Options);



class DerivedFromBase : Base { }
class Base
{
    private readonly List<int> _itmes;
    public Base()
    {
        _itmes = new();
    }
    public void Add(int value)
    {
        _itmes.Add(value);
    }
}

Expected behavior

field _items in deserialized has 1 item.

Actual behavior

field _items in deserialized has 0 items.

• Version used: 2.5.140
• Runtime: net6.0

[AArnott]

If you want private fields to be serialized, you need to use the AllowPrivate variant of the resolver.

[QsROg8320]

If you want private fields to be serialized, you need to use the AllowPrivate variant of the resolver.

it doesn't work too.

DerivedFromBase message = new DerivedFromBase();
message.Add(0);

var bytes = MessagePackSerializer.Serialize(message, ContractlessStandardResolverAllowPrivate.Options);
var deserialized = MessagePackSerializer.Deserialize<DerivedFromBase>(bytes, ContractlessStandardResolverAllowPrivate.Options);

class DerivedFromBase : Base { }
class Base
{
    private readonly List<int> _itmes;
    public Base()
    {
        _itmes = new();
    }
    public void Add(int value)
    {
        _itmes.Add(value);
    }
}

But if we serialize the base class, everything works fine.

Base message = new Base();
message.Add(0);

var bytes = MessagePackSerializer.Serialize(message, TypelessContractlessStandardResolver.Options);
var deserialized = MessagePackSerializer.Deserialize<Base>(bytes, TypelessContractlessStandardResolver.Options);

In this case, _items field is not empty.

[AArnott]

Thank you for trying that out. Sounds like a bug. Albeit, IMO the contractless resolver does a poor job in general. It can't/shouldn't serialize all fields and all properties, because that would involve a lot of redundancy since properties are typically backed by fields. So I recommend (with or without this bug) that you apply the attributes if you own the type, or write a custom formatter if you don't.

[topsterde]

I also ran into the same Bug...