fix: second part

This migrates the NetworkList specific script from NetworkBehaviour.InternalOnNetworkSpawn into NetworkList itself.

It also provides (currently) two internal virtual methods, NetworkVariableBase.OnSpawned and NetworkVariableBase.OnPreDespawn, to provide a means for NetworkList to handle cleaning its dirty state up after the instance with write permissions has finished running through the spawn stages (pre-spawn, spawning, post-spawn, gets invoked).

Author: NoelStephensUnity

com.unity.netcode.gameobjects/Runtime/Core/NetworkBehaviour.cs

@@ -810,6 +810,13 @@ internal void NetworkPostSpawn()
             {
                 Debug.LogException(e);
             }
+
+            // Let each NetworkVariableBase derived instance know that
+            // all spawn related methods have been invoked.
+            for (int i = 0; i < NetworkVariableFields.Count; i++)
+            {
+                NetworkVariableFields[i].OnSpawned();
+            }
         }
 
         internal void NetworkSessionSynchronized()
@@ -847,6 +854,13 @@ internal void InternalOnNetworkPreDespawn()
             {
                 Debug.LogException(e);
             }
+
+            // Let each NetworkVariableBase derived instance know that
+            // all spawn related methods have been invoked.
+            for (int i = 0; i < NetworkVariableFields.Count; i++)
+            {
+                NetworkVariableFields[i].OnPreDespawn();
+            }
         }
 
         internal void InternalOnNetworkDespawn()

com.unity.netcode.gameobjects/Runtime/NetworkVariable/Collections/NetworkList.cs

@@ -58,6 +58,20 @@ public NetworkList(IEnumerable<T> values = default,
             Dispose();
         }
 
+        internal override void OnSpawned()
+        {
+            // If we are dirty and have write permissions by the time the NetworkObject
+            // is finished spawning (same frame), then go ahead and reset the dirty related
+            // properties for NetworkList.
+            if (IsDirty() && CanSend())
+            {
+                UpdateLastSentTime();
+                ResetDirty();
+                SetDirty(false);
+            }
+            base.OnSpawned();
+        }
+
         /// <inheritdoc cref="NetworkVariable{T}.ResetDirty"/>
         public override void ResetDirty()
         {

com.unity.netcode.gameobjects/Runtime/NetworkVariable/NetworkVariableBase.cs

@@ -140,6 +140,28 @@ public void Initialize(NetworkBehaviour networkBehaviour)
             }
         }
 
+        /// TODO-API: After further vetting and alignment on these, we might make them part of the public API.
+        /// Could actually be like an interface that gets automatically registered for these kinds of notifications
+        /// without having to be a NetworkBehaviour.
+        #region OnSpawn and OnPreDespawn (ETC)
+
+        /// <summary>
+        /// Invoked after the associated <see cref="NetworkBehaviour.OnNetworkPostSpawn"/> has been invoked.
+        /// </summary>
+        internal virtual void OnSpawned()
+        {
+
+        }
+
+        /// <summary>
+        /// Invoked after the associated <see cref="NetworkBehaviour.OnNetworkPreDespawn"/> has been invoked.
+        /// </summary>
+        internal virtual void OnPreDespawn()
+        {
+
+        }
+        #endregion
+
         /// <summary>
         /// Deinitialize is invoked when a NetworkObject is despawned.
         /// This allows for a recyled NetworkObject (in-scene or pooled)