From aecc8f258739006ddb261619fdf18f5ccdf08de3 Mon Sep 17 00:00:00 2001
From: MrGadget <9826063+MrGadget1024@users.noreply.github.com>
Date: Sat, 23 Mar 2024 12:09:00 -0400
Subject: [PATCH] fix(SyncList): Clear after Callback Allows users to iterate
 the list before it's wiped

---
 Assets/Mirror/Core/SyncList.cs                         |  8 ++++++--
 .../Tests/Editor/SyncCollections/SyncListTest.cs       | 10 ++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/Assets/Mirror/Core/SyncList.cs b/Assets/Mirror/Core/SyncList.cs
index c8d9c653f..81d0e4066 100644
--- a/Assets/Mirror/Core/SyncList.cs
+++ b/Assets/Mirror/Core/SyncList.cs
@@ -192,12 +192,14 @@ public override void OnDeserializeDelta(NetworkReader reader)
                     case Operation.OP_CLEAR:
                         if (apply)
                         {
-                            objects.Clear();
                             // add dirty + changes.
                             // ClientToServer needs to set dirty in server OnDeserialize.
                             // no access check: server OnDeserialize can always
                             // write, even for ClientToServer (for broadcasting).
                             AddOperation(Operation.OP_CLEAR, 0, default, default, false);
+                            // clear after invoking the callback so users can iterate the list
+                            // and take appropriate action on the items before they are wiped.
+                            objects.Clear();
                         }
                         break;
 
@@ -267,8 +269,10 @@ public void AddRange(IEnumerable<T> range)
 
         public void Clear()
         {
-            objects.Clear();
             AddOperation(Operation.OP_CLEAR, 0, default, default, true);
+            // clear after invoking the callback so users can iterate the list
+            // and take appropriate action on the items before they are wiped.
+            objects.Clear();
         }
 
         public bool Contains(T item) => IndexOf(item) >= 0;
diff --git a/Assets/Mirror/Tests/Editor/SyncCollections/SyncListTest.cs b/Assets/Mirror/Tests/Editor/SyncCollections/SyncListTest.cs
index 429d33001..7596f1897 100644
--- a/Assets/Mirror/Tests/Editor/SyncCollections/SyncListTest.cs
+++ b/Assets/Mirror/Tests/Editor/SyncCollections/SyncListTest.cs
@@ -97,9 +97,19 @@ public void TestAddRange()
         [Test]
         public void TestClear()
         {
+            bool called = false;
+            clientSyncList.Callback = (op, index, oldItem, newItem) =>
+            {
+                called = true;
+
+                Assert.That(op, Is.EqualTo(SyncList<string>.Operation.OP_CLEAR));
+                Assert.That(clientSyncList.Count, Is.EqualTo(3));
+            };
+
             serverSyncList.Clear();
             SerializeDeltaTo(serverSyncList, clientSyncList);
             Assert.That(clientSyncList, Is.EquivalentTo(new string[] {}));
+            Assert.That(called, Is.True);
         }
 
         [Test]