perf: reduce diagnostics and queued dispatch allocations in 2.3.2

Runtime/EventBus.cs

@@ -57,6 +57,8 @@ namespace ShrinkEventBus
         private static readonly IShrinkEventBus DefaultBus = CreateDefaultBus();
         private static Action<IShrinkEvent, Type, ShrinkBusKey>? _posted;
         private static Action<ShrinkEventTrace>? _detailedPosted;
+        private static readonly object DetailedObserverGate = new();
+        private static Action<ShrinkEventTrace>[]? _detailedObserverSnapshot;
 
         internal static event Action<IShrinkEvent, Type, ShrinkBusKey> Posted
         {
@@ -78,14 +80,41 @@ namespace ShrinkEventBus
 
         internal static event Action<ShrinkEventTrace> DetailedPosted
         {
-            add => _detailedPosted += value;
-            remove => _detailedPosted -= value;
+            add
+            {
+                lock (DetailedObserverGate)
+                {
+                    _detailedPosted += value;
+                    PublishDetailedObserverSnapshot();
+                }
+            }
+            remove
+            {
+                lock (DetailedObserverGate)
+                {
+                    _detailedPosted -= value;
+                    PublishDetailedObserverSnapshot();
+                }
+            }
+        }
+
+        private static void PublishDetailedObserverSnapshot()
+        {
+            var invocationList = _detailedPosted?.GetInvocationList();
+            Action<ShrinkEventTrace>[]? snapshot = null;
+            if (invocationList != null)
+            {
+                snapshot = new Action<ShrinkEventTrace>[invocationList.Length];
+                for (var i = 0; i < snapshot.Length; i++)
+                    snapshot[i] = (Action<ShrinkEventTrace>)invocationList[i];
+            }
+            Volatile.Write(ref _detailedObserverSnapshot, snapshot);
         }
 
         internal static bool HasDetailedPostedObservers
         {
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            get => Volatile.Read(ref _detailedPosted) != null;
+            get => Volatile.Read(ref _detailedObserverSnapshot) != null;
         }
 
         public static IShrinkEventBus Default => DefaultBus;
@@ -212,15 +241,14 @@ namespace ShrinkEventBus
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         internal static void NotifyDetailedPosted(ShrinkEventTrace trace)
         {
-            var observers = Volatile.Read(ref _detailedPosted);
+            var observers = Volatile.Read(ref _detailedObserverSnapshot);
             if (observers == null)
                 return;
-            var invocationList = observers.GetInvocationList();
-            for (var i = 0; i < invocationList.Length; i++)
+            for (var i = 0; i < observers.Length; i++)
             {
                 try
                 {
-                    ((Action<ShrinkEventTrace>)invocationList[i])(trace);
+                    observers[i](trace);
                 }
                 catch (Exception exception)
                 {