Merge pull request Cysharp#218 from Cysharp/feature/CleanStackTrace

Hide a invoke filter helper method in a stack trace.

src/MagicOnion/Server/Hubs/StreamingHubHandler.cs

@@ -167,8 +167,7 @@ Func<StreamingHubContext, ValueTask> BuildMethodBodyWithFilter(Func<StreamingHub
             foreach (var filterFactory in this.filters.Reverse())
             {
                 var newFilter = filterFactory.CreateInstance(serviceLocator);
-                var next_ = next; // capture reference
-                next = (ctx) => newFilter.Invoke(ctx, next_);
+                next = new InvokeHelper<StreamingHubContext, Func<StreamingHubContext, ValueTask>>(newFilter.Invoke, next).GetDelegate();
             }
 
             return next;

src/MagicOnion/Server/InvokeHelper.cs

@@ -0,0 +1,73 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Reflection.Emit;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace MagicOnion.Server
+{
+    internal class InvokeHelper<TArg1, TDelegate>
+        where TDelegate : Delegate
+    {
+        public Func<TArg1, TDelegate, ValueTask> Invoke;
+        public TDelegate Next;
+
+        private static readonly Func<InvokeHelper<TArg1, TDelegate>, TDelegate> InvokeNextFactory;
+
+        static InvokeHelper()
+        {
+            var fieldInvoke = typeof(InvokeHelper<TArg1, TDelegate>).GetField("Invoke");
+            var fieldNext = typeof(InvokeHelper<TArg1, TDelegate>).GetField("Next");
+            var methodInvoke = typeof(Func<TArg1, TDelegate, ValueTask>).GetMethod("Invoke");
+
+            if (RuntimeInformation.FrameworkDescription.StartsWith(".NET Core 4")) /* .NET Core 2.x returns ".NET Core 4.x.y.z" */
+            {
+                // HACK: If the app is running on .NET Core 2.2 or earlier, the runtime hides dynamic method in the stack trace.
+                var method = new DynamicMethod("InvokeNext", typeof(ValueTask), new[] { typeof(InvokeHelper<TArg1, TDelegate>), typeof(TArg1) }, restrictedSkipVisibility: true);
+                {
+                    var il = method.GetILGenerator();
+
+                    // invoke = arg0.Invoke;
+                    il.Emit(OpCodes.Ldarg_0);
+                    il.Emit(OpCodes.Ldfld, fieldInvoke);
+
+                    // next = arg0.Next;
+                    // return invoke(arg1, next);
+                    il.Emit(OpCodes.Ldarg_1);
+                    il.Emit(OpCodes.Ldarg_0);
+                    il.Emit(OpCodes.Ldfld, fieldNext);
+                    il.Emit(OpCodes.Callvirt, methodInvoke);
+                    il.Emit(OpCodes.Ret);
+                }
+
+                InvokeNextFactory = (helper) => (TDelegate)method.CreateDelegate(typeof(TDelegate), helper);
+
+            }
+            else
+            {
+                // HACK: If the app is running on .NET Core 3.0 or later, the runtime hides `AggressiveInlining` method in the stack trace. (If the app is running on .NET Framework 4.x, This hack does not affect.)
+                // https://github.com/dotnet/coreclr/blob/release/3.0/src/System.Private.CoreLib/shared/System/Diagnostics/StackTrace.cs#L343-L350
+                InvokeNextFactory = (helper) =>
+                {
+                    var invokeNext = new Func<TArg1, ValueTask>(helper.InvokeNext);
+                    return (TDelegate)Delegate.CreateDelegate(typeof(TDelegate), invokeNext.Target, invokeNext.Method);
+                };
+            }
+        }
+
+        public InvokeHelper(Func<TArg1, TDelegate, ValueTask> invoke, TDelegate next)
+        {
+            Invoke = invoke;
+            Next = next;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        [DebuggerHidden]
+        private ValueTask InvokeNext(TArg1 arg1) => Invoke(arg1, Next);
+
+        public TDelegate GetDelegate() => InvokeNextFactory(this);
+    }
+}

src/MagicOnion/Server/MethodHandler.cs

@@ -292,8 +292,7 @@ Func<ServiceContext, ValueTask> BuildMethodBodyWithFilter(Func<ServiceContext, V
             foreach (var filterFactory in this.filters.Reverse())
             {
                 var newFilter = filterFactory.CreateInstance(serviceLocator);
-                var next_ = next; // capture reference
-                next = (ctx) => newFilter.Invoke(ctx, next_);
+                next = new InvokeHelper<ServiceContext, Func<ServiceContext, ValueTask>>(newFilter.Invoke, next).GetDelegate();
             }
 
             return next;