Extra value is added to the value passed by spawnPayload

[sowa-s]

Describe the bug:
Passing spawnPayload to NetworkObject#Spaw(Steam) and reading stream from NetworkBehavior#NetworkStart(Stream), extra values are added.

Steps to reproduce the behavior:

1. call Spawn method with spawnPayload.

var obj = Instantiate(SomePrefab);
var stream = new MemoryStream(Encoding.UTF8.GetBytes("helloworld"));
obj.GetComponent<NetworkedObject>().Spawn(stream.Stream);

2. Read the value in NetworkStart

public override void NetworkStart(Stream stream)
{
    base.NetworkStart(stream);
    var memoryStream = new MemoryStream();
    stream.CopyTo(memoryStream);
    var message = Encoding.UTF8.GetString(memoryStream.ToArray());
    Debug.Log(message);
}

3. The log will be output as hello with a mysterious message.

helloworld��Dt`XD�����䒈Dt�D�����DtDpblld�f�Z�hfpZhhhhZ��p�Zrf��lbbln�r�D��

Expected behavior:

I think only helloworld should be output.

Desktop/Tablet/Smartphone (please complete the following information):

• OS: [e.g. iOS] windows10
• MLAPI v12.1.7
• Unity 2020.2.3.f1

Additional info:

Perhaps this problem is caused by something here in the code.
The buffer will be partially overwritten and extra information will be left behind.

if (payload != null) buffer.CopyFrom(payload);

https://github.com/Unity-Technologies/com.unity.multiplayer.mlapi/blob/023b64aeecaeee7461bdf989000ff9a796cfde1b/com.unity.multiplayer.mlapi/Runtime/Spawning/NetworkSpawnManager.cs#L511

[LukeStampfli]

What's StringStream? Are you sure that stream is not adding additional compression or something like that? Try passing the MemoryStream directly into the payload

[sowa-s]

Sorry, StringStream is a mistake. The original code passed the MemoryStream directly.
The code shown in the issue has been modified.

[NoelStephensUnity]

Hi sowa-s,
I think you would have better success with this code:
#1: call Spawn method with spawnPayload.

var spawnDataPooledBuffer = PooledNetworkBuffer.Get();
var spawnDataWriter = PooledNetworkWriter.Get(spawnDataPooledBuffer);
spawnDataWriter.WriteByteArray(Encoding.UTF8.GetBytes("hello world"));

#2: Read the value in NetworkStart

public override void NetworkStart(Stream stream)
{
    base.NetworkStart(stream);        
    var streamReader = PooledNetworkReader.Get(stream);
    var dataSent = streamReader.ReadByteArray();
    var message = Encoding.UTF8.GetString(dataSent);
    Debug.Log(message);
}

Just using a stream the way you were doesn't include storing information about how many bytes were written into the stream.
If you use the MLAPI NetworkWriters and NetworkReaders then it handles all of that for you.
The above code yields this result in the console window every time:

Let me know if this addresses your issue?

[NoelStephensUnity]

You can no longer pass a payload when spawning in V1.0.0