protobuf-net deserialize fails when using ReadOnlyMemory

Question

I can deserialize when passing a stream, but if I pass a ReadOnlyMemory instance instead of a stream, I get a ProtoException "Invalid wire type (VarInt)" Why?

Protobuf-net version 3.1.26

repro:

            using (var stream = new MemoryStream())
        {
            var test = 1;
            Serializer.Serialize(stream, test);

            // save off bytes for later comparison
            var bytes = stream.ToArray();

            // this succeeds
            stream.Seek(0, SeekOrigin.Begin);
            var item = Serializer.Deserialize<int>(stream);

            // this succeeds
            stream.Seek(0, SeekOrigin.Begin);
            var item2 = Serializer.Deserialize(typeof(int), stream);


            stream.Seek(0, SeekOrigin.Begin);
            var rom = new ReadOnlySpan<byte>(stream.ToArray());
            // sanity check: newBytes should be equal to bytes, and it is. 
            var newBytes = rom.ToArray();

            // this fails with ProtoException "Invalid wire-type (Varint)..."
            var item3 = Serializer.Deserialize(rom, typeof(int));
            
        }

Answer 1

Can you try Serializer.Deserialize<int>(rom)? I wonder if your call is doing Deserialize<Type> via the second parameter being interpreted as an existing object.

If you need a non-generic API:

ProtoBuf.Serializer.NonGeneric.Deserialize(type, rom);