'NonSerialized' field-targeted attribute is not honored by generated serializer

[Elihpmap-Magic]

General
Unity version: 6.0 (6000.0.47f1)
Fish-Networking version: First found on 4.6.1, still replicated on 4.6.9
Discord link: I'm not on the community Discord, I kinda disagree on hiding the community ressources on private servers (even if I understand the utility of instant messages, I believe a publicly available forum would be better). I would rather discuss directly on this public issue report if needed. You can also contact me by mail if something requires a private discussion.

Description
When adding System.NonSerialized as a field-targeted attribute to a public property with a backing field. The value is still serialized and transmitted over the network.

Replication
Steps to reproduce the behaviour with the given example:

1. Load the ReplicatingPropertyIssue scene in a Unity project with FishnetPro (this uses Yak to easily test that locally)
2. Start playmode
3. Check the console for the warning log with the different deserialized value : notice that NonReplicatedProperty is true instead of false.

Steps to reproduce the behavior generally:

1. Create a classe with a backing-field property with the fild targeted attribute System.NonSerialized

like so for example: [field: System.NonSerialized] public bool TestBoolProperty {get; set;} = false

2. Send an instance of this class with the property set to a different value than its default one via a FishNet RPC
3. On the receiving end check the value of the property in the received class instance : the property is not to its default value but the one set on the rpc-calling side.

Expected behavior
Public field-backed properties with attribute [field: System.NonSerialized] should not be serialized (or at least not send over the network).

Example content
The example contains a simple scene and a unique script (retranscribed just below for easy access) to test this behaviour with a simple host configuration using Yak transport layer.

ReplicatingPropertyIssue.zip

single script content

TestHostBehaviour.cs :

using System;
using FishNet.Managing.Client;
using FishNet.Managing.Server;
using FishNet.Object;
using UnityEngine;

public class TestHostBehaviour : NetworkBehaviour
{
    public ServerManager server;
    public ClientManager client;
    void OnEnable()
    {
        server.StartConnection();
        client.StartConnection();
    }

    public override void OnStartClient()
    {
        ObserversRpc_ReplicateOnAllObserver(SemiReplicableClass.CreateAtOrigin());
    }

    [Serializable]
    public class SemiReplicableClass
    {
        public bool replicatedVariable = false;
        public bool ReplicatedProperty {get; set;} = false;
        [NonSerialized] public bool nonReplicatedVariable = false;
        [field: NonSerialized] public bool NonReplicatedProperty {get; set;} = false; //This is still replicated! (workaround : add 'private' accessor to the setter)

        public static SemiReplicableClass CreateAtOrigin()
        {
            return new() 
            {
                replicatedVariable = true, 
                ReplicatedProperty = true,
                nonReplicatedVariable = true,
                NonReplicatedProperty = true,
            };
        }
    }

    [ObserversRpc(RunLocally = false)] //Set RunLocally to true to test without semiReplicableClass replication (all values return true)
    public void ObserversRpc_ReplicateOnAllObserver(SemiReplicableClass semiReplicableClass)
    {
        Debug.LogWarning($"replicatedVariable = {semiReplicableClass.replicatedVariable}\n" +
            $"ReplicatedProperty = {semiReplicableClass.ReplicatedProperty}\n" +
            $"nonReplicatedVariable = {semiReplicableClass.nonReplicatedVariable}\n" +
            $"NonReplicatedProperty = {semiReplicableClass.NonReplicatedProperty}");

            //This prints:
            // replicatedVariable = True
            // ReplicatedProperty = True
            // nonReplicatedVariable = False
            // NonReplicatedProperty = True
    }
}

[FirstGearGames]

NonSerialized is still sent because you might want to set a value at run-time, and have it still send over the network, such as in a class or structure.

Using [ExcludeSerialization] will prevent it from being serialized.

[Elihpmap-Magic]

Hi! Thanks for the answer!

However I feel like I'm missing a few things to understand it:

• The NonSerialized attribute doesn't prevent in any way to set the value of the targeted variable at runtime? In the opposite case, for a property, adding [field: UnityEngine.SerializeField] will allow to set the value in editor via the inspector. But I don't see how that would negate the fact that it can be set at runtime?
• As said in the documentation the NonSerialized attribute is supposed to be used to mark variables that should not be considered by the automatic serialization. This works as described (or at least as I expected after reading the doc) for normal fields (as can be seen in the example I created for this issue with the variable nonReplicatedVariable), why should this be different for backing-field properties ?
• Additionnaly (but I admit that this is less important) I couldn't find any reference to ExcludeSerialization attribute in the documentation. But I think I see the value in being able to mark some variable to not be serialized only by FishNet automatic serialization but being serialized for other uses (such as Unity inspector availablity for example). If that's the use intended for having a discrete attribute with the same role as NonSerialized (but in a specific context only), why not publicise it in the documentation? the problem I see with this alternate solution of embracing this ExcludeSerialization attribute as the only valid marker for this situation is that I would also expect that change to require a potentially breaking change to stay consistent: FishNet should then automaticaly serialize regular fields with the NonSerialized attribute but not the ExcludeSerialization one even though it didn't before (see question 2 and the nonReplicatedVariable in my example)

If you have any insight to enlighten me about these questions I would be very grateful! Because for now I don't see how this could be "working as intended".

Thanks for your time, and have a great day!

[FirstGearGames]

NonSerialized should still be sent over the network.

ExcludeSerialization (the FishNet attribute) should prevent network serialization.

With you saying NonSerialized works on fields but not properties suggests FishNet is improperly blocking serialization of fields. ExcludeSerialization did not always exist, so this might be the case and is a bug if so.

The documentation was mistaken and will be corrected soon - it pre-dated the ExcludeSerialization change.

NonSerialized is still sent because you might want to set a value at run-time, and have it still send over the network, such as in a class or structure.

Using [ExcludeSerialization] will prevent it from being serialized.

I believe this ^ was misunderstood. NonSerialized should be sent because even though it prevents an object from being serialized in the inspector you can still change it at runtime.

[FirstGearGames]

Resolved in 4.6.10 -- Fields are no longer excluded when using NonSerialized. Properties and Fields are correctly excluded when using ExcludeSerialization.