feat: adding bool for InitialState

flag that can be used inside syncvar hooks to tell if it is the spawn payload or not

Assets/Mirage/Runtime/NetworkIdentity.cs

@@ -187,6 +187,12 @@ public sealed class NetworkIdentity : MonoBehaviour
         /// </summary>
         public NetworkWorld World { get; internal set; }
 
+        /// <summary>
+        /// True while applying spawn payload within OnDeserializeAll
+        /// <para>Can be used inside syncvar hooks to tell if object has just spawned</para>
+        /// </summary>
+        public bool InitialState { get; private set; }
+
         [Header("Runtime References")]
 
         /// <summary>
@@ -714,6 +720,8 @@ private void OnDeserialize(NetworkBehaviour comp, NetworkReader reader, bool ini
 
         internal void OnDeserializeAll(NetworkReader reader, bool initialState)
         {
+            InitialState = initialState;
+
             // deserialize all components that were received
             var components = NetworkBehaviours;
             // check if we can read at least 1 byte
@@ -729,6 +737,8 @@ internal void OnDeserializeAll(NetworkReader reader, bool initialState)
                     OnDeserialize(components[index], reader, initialState);
                 }
             }
+
+            InitialState = false;
         }
 
         internal void SetServerValues(NetworkServer networkServer, ServerObjectManager serverObjectManager)

Assets/Tests/Runtime/SyncVarInitialStateFlagTest.cs

@@ -0,0 +1,56 @@
+using System;
+using Mirage.Serialization;
+using NUnit.Framework;
+
+namespace Mirage.Tests.Runtime
+{
+    public class SyncVarInitialStateFlagBehaviour : NetworkBehaviour
+    {
+        public event Action<int> Hook;
+
+        [SyncVar(hook = nameof(Hook))]
+        public int number;
+    }
+    public class SyncVarInitialStateFlagTest : TestBase
+    {
+        private readonly NetworkWriter ownerWriter = new NetworkWriter(1300);
+        private readonly NetworkWriter observersWriter = new NetworkWriter(1300);
+        private readonly NetworkReader reader = new NetworkReader();
+
+        [TearDown]
+        public void TearDown()
+        {
+            TearDownTestObjects();
+
+            ownerWriter.Reset();
+            observersWriter.Reset();
+            reader.Dispose();
+        }
+
+        [Test]
+        [TestCase(true)]
+        [TestCase(false)]
+        public void InitialStateHasCorrectValue(bool input)
+        {
+            var server = CreateBehaviour<SyncVarInitialStateFlagBehaviour>();
+            var client = CreateBehaviour<SyncVarInitialStateFlagBehaviour>();
+
+            server.number = 10;
+
+            var invoked = 0;
+            var result = false;
+            client.Hook += (_) =>
+            {
+                invoked++;
+                result = client.Identity.InitialState;
+            };
+
+            server.Identity.OnSerializeAll(input, ownerWriter, observersWriter);
+            reader.Reset(observersWriter.ToArraySegment());
+            client.Identity.OnDeserializeAll(reader, input);
+
+            Assert.That(invoked, Is.EqualTo(1));
+            Assert.That(result, Is.EqualTo(input));
+        }
+    }
+}