Protobuf-net.Protogen问题带有自定义选项

Question

顾名思义，我最近一直在尝试将自定义选项添加到我的某些.proto文件中。但是，似乎生成的C＃代码包含CS1503错误。

这是使用独立的原始工具

syntax = "proto3";
import "google/protobuf/descriptor.proto";

extend google.protobuf.FieldOptions {
    optional int32 my_custom_int = 50001;
}

message MyMessage {
    optional int32 my_int = 1 [(my_custom_int) = 5];
}

和生成的C＃结果的一个示例：

// <auto-generated>
//   This file was generated by a tool; you should avoid making direct changes.
//   Consider using 'partial classes' to extend these types
//   Input: my.proto
// </auto-generated>

#region Designer generated code
#pragma warning disable CS0612, CS0618, CS1591, CS3021, IDE0079, IDE1006, RCS1036, RCS1057, RCS1085, RCS1192
[global::ProtoBuf.ProtoContract()]
public partial class MyMessage : global::ProtoBuf.IExtensible
{
    private global::ProtoBuf.IExtension __pbn__extensionData;
    global::ProtoBuf.IExtension global::ProtoBuf.IExtensible.GetExtensionObject(bool createIfMissing)
        => global::ProtoBuf.Extensible.GetExtensionObject(ref __pbn__extensionData, createIfMissing);

    [global::ProtoBuf.ProtoMember(1, Name = @"my_int")]
    public int MyInt
    {
        get => __pbn__MyInt.GetValueOrDefault();
        set => __pbn__MyInt = value;
    }
    public bool ShouldSerializeMyInt() => __pbn__MyInt != null;
    public void ResetMyInt() => __pbn__MyInt = null;
    private int? __pbn__MyInt;

}

public static partial class Extensions
{
    public static int GetMyCustomInt(this global::Google.Protobuf.Reflection.FieldOptions obj)
        => obj == null ? default : global::ProtoBuf.Extensible.GetValue<int>(obj, 50001);

    public static void SetMyCustomInt(this global::Google.Protobuf.Reflection.FieldOptions obj, int value)
        => global::ProtoBuf.Extensible.AppendValue<int>(obj, 50001, value);

}
#pragma warning restore CS0612, CS0618, CS1591, CS3021, IDE0079, IDE1006, RCS1036, RCS1057, RCS1085, RCS1192
#endregion

这里的问题是，Visual Studio将CS1503错误作为ProtoBuf.extensible.AppendValue（）期望iextensible ，哪个fieldOptions不是。

我对Protobuf的新手相对较新，对于问题的来源而言，我有点不知所措。我是否忘记了.proto声明的一部分，还是protobuf-net.protogen不支持自定义选项？