[generator] Eliminate usage of JNINativeWrapper.CreateDelegate in bindings.

src/Java.Interop/Java.Interop/JniEnvironment.cs

@@ -3,6 +3,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
@@ -50,6 +51,50 @@ public      static  bool                    WithinNewObjectScope {
 			internal set {CurrentInfo.WithinNewObjectScope = value;}
 		}
 
+		[global::System.Diagnostics.CodeAnalysis.SuppressMessage (
+			"Design",
+			"CA1031:Do not catch general exception types",
+			Justification = "Exceptions cannot cross a JNI boundary.")]
+		public static bool BeginMarshalMethod (IntPtr jnienv, out JniTransition transition, [NotNullWhen (true)] out JniRuntime? runtime)
+		{
+			runtime = null;
+			Exception?          ex  = null;
+			try {
+				runtime = Info.Value?.Runtime;
+			}
+			catch (Exception e) {
+				ex  = e;
+			}
+			if (runtime == null || ex != null) {
+				transition  = default;
+				runtime     = null;
+				Console.Error.WriteLine ("JNI Environment Information is not available on this thread.");
+				if (ex != null) {
+					Console.Error.WriteLine (ex);
+				}
+				return false;
+			}
+
+			try {
+				runtime.OnEnterMarshalMethod ();
+				transition  = new JniTransition (jnienv);
+			}
+			catch (Exception e) {
+				runtime     = null;
+				transition  = default;
+
+				Console.Error.WriteLine ($"OnEnterMarshalMethod failed: {e}");
+				return false;
+			}
+
+			return true;
+		}
+
+		public static void EndMarshalMethod (ref JniTransition transition)
+		{
+			transition.Dispose ();
+		}
+
 		internal    static  void    SetEnvironmentPointer (IntPtr environmentPointer)
 		{
 			CurrentInfo.EnvironmentPointer  = environmentPointer;

src/Java.Interop/Java.Interop/JniRuntime.cs

@@ -437,6 +437,19 @@ public virtual bool ExceptionShouldTransitionToJni (Exception e)
 
 	partial class JniRuntime {
 
+		public virtual void OnEnterMarshalMethod ()
+		{
+			ValueManager.WaitForGCBridgeProcessing ();
+		}
+
+		public virtual void OnUserUnhandledException (ref JniTransition transition, Exception e)
+		{
+			transition.SetPendingException (e);
+
+			// TODO: Enable when we move to 'net9.0'
+			//Debugger.BreakForUserUnhandledException (e);
+		}
+
 		public virtual void RaisePendingException (Exception pendingException)
 		{
 			JniEnvironment.Exceptions.Throw (pendingException);

src/Java.Interop/PublicAPI.Unshipped.txt

@@ -1 +1,5 @@
 #nullable enable
+static Java.Interop.JniEnvironment.BeginMarshalMethod(nint jnienv, out Java.Interop.JniTransition transition, out Java.Interop.JniRuntime? runtime) -> bool
+static Java.Interop.JniEnvironment.EndMarshalMethod(ref Java.Interop.JniTransition transition) -> void
+virtual Java.Interop.JniRuntime.OnEnterMarshalMethod() -> void
+virtual Java.Interop.JniRuntime.OnUserUnhandledException(ref Java.Interop.JniTransition transition, System.Exception! e) -> void

tests/generator-Tests/SupportFiles/DebuggerDisableUserUnhandledExceptionsAttribute.cs

@@ -0,0 +1,13 @@
+#if !NET9_0_OR_GREATER
+
+using System;
+
+namespace System.Diagnostics
+{
+	// This attribute was added in .NET 9, and we may not be targeting .NET 9 yet.
+	public class DebuggerDisableUserUnhandledExceptionsAttribute : Attribute
+	{
+	}
+}
+
+#endif  // !NET9_0_OR_GREATER

tests/generator-Tests/Unit-Tests/CodeGeneratorExpectedResults/Common/WriteDuplicateInterfaceEventArgs.txt

@@ -70,15 +70,24 @@ internal partial class AnimatorListenerInvoker : global::Java.Lang.Object, Anima
 #pragma warning disable 0169
 	static Delegate GetOnAnimationEnd_IHandler ()
 	{
-		if (cb_OnAnimationEnd_OnAnimationEnd_I_Z == null)
-			cb_OnAnimationEnd_OnAnimationEnd_I_Z = JNINativeWrapper.CreateDelegate (new _JniMarshal_PPI_Z (n_OnAnimationEnd_I));
-		return cb_OnAnimationEnd_OnAnimationEnd_I_Z;
+		return cb_OnAnimationEnd_OnAnimationEnd_I_Z ??= new _JniMarshal_PPI_Z (n_OnAnimationEnd_I);
 	}
 
+	[global::System.Diagnostics.DebuggerDisableUserUnhandledExceptions]
 	static bool n_OnAnimationEnd_I (IntPtr jnienv, IntPtr native__this, int param1)
 	{
-		var __this = global::Java.Lang.Object.GetObject<java.code.AnimatorListener> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
-		return __this.OnAnimationEnd (param1);
+		if (!global::Java.Interop.JniEnvironment.BeginMarshalMethod (jnienv, out var __envp, out var __r))
+			return default;
+
+		try {
+			var __this = global::Java.Lang.Object.GetObject<java.code.AnimatorListener> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
+			return __this.OnAnimationEnd (param1);
+		} catch (global::System.Exception __e) {
+			__r.OnUserUnhandledException (ref __envp, __e);
+			return default;
+		} finally {
+			global::Java.Interop.JniEnvironment.EndMarshalMethod (ref __envp);
+		}
 	}
 #pragma warning restore 0169
 
@@ -96,15 +105,24 @@ internal partial class AnimatorListenerInvoker : global::Java.Lang.Object, Anima
 #pragma warning disable 0169
 	static Delegate GetOnAnimationEnd_IIHandler ()
 	{
-		if (cb_OnAnimationEnd_OnAnimationEnd_II_Z == null)
-			cb_OnAnimationEnd_OnAnimationEnd_II_Z = JNINativeWrapper.CreateDelegate (new _JniMarshal_PPII_Z (n_OnAnimationEnd_II));
-		return cb_OnAnimationEnd_OnAnimationEnd_II_Z;
+		return cb_OnAnimationEnd_OnAnimationEnd_II_Z ??= new _JniMarshal_PPII_Z (n_OnAnimationEnd_II);
 	}
 
+	[global::System.Diagnostics.DebuggerDisableUserUnhandledExceptions]
 	static bool n_OnAnimationEnd_II (IntPtr jnienv, IntPtr native__this, int param1, int param2)
 	{
-		var __this = global::Java.Lang.Object.GetObject<java.code.AnimatorListener> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
-		return __this.OnAnimationEnd (param1, param2);
+		if (!global::Java.Interop.JniEnvironment.BeginMarshalMethod (jnienv, out var __envp, out var __r))
+			return default;
+
+		try {
+			var __this = global::Java.Lang.Object.GetObject<java.code.AnimatorListener> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
+			return __this.OnAnimationEnd (param1, param2);
+		} catch (global::System.Exception __e) {
+			__r.OnUserUnhandledException (ref __envp, __e);
+			return default;
+		} finally {
+			global::Java.Interop.JniEnvironment.EndMarshalMethod (ref __envp);
+		}
 	}
 #pragma warning restore 0169
 

tests/generator-Tests/Unit-Tests/CodeGeneratorExpectedResults/Common/WriteInterfaceRedeclaredDefaultMethod.txt

@@ -66,15 +66,23 @@ internal partial class IMyInterface2Invoker : global::Java.Lang.Object, IMyInter
 #pragma warning disable 0169
 	static Delegate GetDoSomethingHandler ()
 	{
-		if (cb_DoSomething_DoSomething_V == null)
-			cb_DoSomething_DoSomething_V = JNINativeWrapper.CreateDelegate (new _JniMarshal_PP_V (n_DoSomething));
-		return cb_DoSomething_DoSomething_V;
+		return cb_DoSomething_DoSomething_V ??= new _JniMarshal_PP_V (n_DoSomething);
 	}
 
+	[global::System.Diagnostics.DebuggerDisableUserUnhandledExceptions]
 	static void n_DoSomething (IntPtr jnienv, IntPtr native__this)
 	{
-		var __this = global::Java.Lang.Object.GetObject<java.code.IMyInterface2> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
-		__this.DoSomething ();
+		if (!global::Java.Interop.JniEnvironment.BeginMarshalMethod (jnienv, out var __envp, out var __r))
+			return;
+
+		try {
+			var __this = global::Java.Lang.Object.GetObject<java.code.IMyInterface2> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
+			__this.DoSomething ();
+		} catch (global::System.Exception __e) {
+			__r.OnUserUnhandledException (ref __envp, __e);
+		} finally {
+			global::Java.Interop.JniEnvironment.EndMarshalMethod (ref __envp);
+		}
 	}
 #pragma warning restore 0169