System.Text.Json ignores JsonPropertyName on BaseClass

[robertmuehsig]

I'm not sure if this is a bug or by design, but while moving from JSON.NET to System.Text.Json I discovered the following behavior:

"JsonPropertyNames" are ignored on base classes.

    class Program
    {
        static void Main(string[] args)
        {
            RealClass test = new RealClass();

            // output will be "{"Link":"Foo"}" 
            // and not {"_LinkFromBaseClass":"Foo"}

            Console.WriteLine(JsonSerializer.Serialize(test));


            Console.WriteLine("Hello World!");
        }
    }

    public abstract class SomeBaseClass
    {
        [JsonPropertyName("_LinkFromBaseClass")]
        public virtual string Link { get;  }
    }

    public class RealClass : SomeBaseClass
    {
        public RealClass()
        {
        }

        public override string Link { get { return "Foo"; } }
    }

Is this "by design"? Currently we just put the "JsonPropertyName" attribute on all implementations for the baseclass, but it's quite easy to miss.
I also checked the JsonSerializerOptions, but didn't find anything useful, but maybe I miss something.

[Symbai]

It is not support (yet). Similar issues:

https://github.com/dotnet/corefx/issues/41747
https://github.com/dotnet/corefx/issues/39031
https://github.com/dotnet/corefx/issues/41325
https://github.com/dotnet/corefx/issues/38650

[ericstj]

We can consider this when adding support for polymorphic serialization #29937

[eiriktsarpalis]

Duplicate of #51165