Handle reflection exceptions

Author: mattleibow

src/Controls/tests/DeviceTests/Elements/HybridWebView/HybridWebViewTests_ExceptionHandling.cs

@@ -33,45 +33,45 @@ public Task CSharpMethodThatThrowsException_ShouldPropagateToJavaScript() =>
 		});
 
 	[Fact]
-	public Task CSharpMethodThatThrowsCustomException_ShouldIncludeExceptionDetails() =>
+	public Task CSharpAsyncMethodThatThrowsException_ShouldPropagateToJavaScript() =>
 		RunTest("exception-tests.html", async (hybridWebView) =>
 		{
 			var invokeJavaScriptTarget = new TestExceptionMethods();
 			hybridWebView.SetInvokeJavaScriptTarget(invokeJavaScriptTarget);
 
-			// Tell JavaScript to invoke the method that throws a custom exception
-			hybridWebView.SendRawMessage("ThrowCustomException");
+			// Tell JavaScript to invoke the async method that throws an exception
+			hybridWebView.SendRawMessage("ThrowExceptionAsync");
 
 			// Wait for JavaScript to handle the exception
 			await WebViewHelpers.WaitForHtmlStatusSet(hybridWebView);
 
-			// Check that JavaScript caught the exception with custom details
-			var errorType = await hybridWebView.EvaluateJavaScriptAsync("GetLastErrorType()");
-			var errorMessage = await hybridWebView.EvaluateJavaScriptAsync("GetLastErrorMessage()");
+			// Check that JavaScript caught the async exception
+			var caughtError = await hybridWebView.EvaluateJavaScriptAsync("GetLastError()");
+			Assert.Equal("Async test exception", caughtError);
 
-			Assert.Equal("ArgumentException", errorType);
-			Assert.Equal("Custom argument exception", errorMessage);
+			// Check that the method was called before throwing
+			Assert.Equal("ThrowExceptionAsync", invokeJavaScriptTarget.LastMethodCalled);
 		});
 
 	[Fact]
-	public Task CSharpAsyncMethodThatThrowsException_ShouldPropagateToJavaScript() =>
+	public Task CSharpMethodThatThrowsCustomException_ShouldIncludeExceptionDetails() =>
 		RunTest("exception-tests.html", async (hybridWebView) =>
 		{
 			var invokeJavaScriptTarget = new TestExceptionMethods();
 			hybridWebView.SetInvokeJavaScriptTarget(invokeJavaScriptTarget);
 
-			// Tell JavaScript to invoke the async method that throws an exception
-			hybridWebView.SendRawMessage("ThrowExceptionAsync");
+			// Tell JavaScript to invoke the method that throws a custom exception
+			hybridWebView.SendRawMessage("ThrowCustomException");
 
 			// Wait for JavaScript to handle the exception
 			await WebViewHelpers.WaitForHtmlStatusSet(hybridWebView);
 
-			// Check that JavaScript caught the async exception
-			var caughtError = await hybridWebView.EvaluateJavaScriptAsync("GetLastError()");
-			Assert.Equal("Async test exception", caughtError);
+			// Check that JavaScript caught the exception with custom details
+			var errorType = await hybridWebView.EvaluateJavaScriptAsync("GetLastErrorType()");
+			var errorMessage = await hybridWebView.EvaluateJavaScriptAsync("GetLastErrorMessage()");
 
-			// Check that the method was called before throwing
-			Assert.Equal("ThrowExceptionAsync", invokeJavaScriptTarget.LastMethodCalled);
+			Assert.Equal("ArgumentException", errorType);
+			Assert.Equal("Custom argument exception", errorMessage);
 		});
 
 	[Fact]
@@ -89,11 +89,11 @@ public Task CSharpMethodThatSucceeds_ShouldStillWorkNormally() =>
 
 			// Check that JavaScript got the normal result
 			var result = await hybridWebView.EvaluateJavaScriptAsync("GetLastResult()");
-			Assert.Equal("Success!", result);
+			Assert.Contains("Success!", result, StringComparison.Ordinal);
 
 			// Check that no error was thrown
 			var hasError = await hybridWebView.EvaluateJavaScriptAsync("HasError()");
-			Assert.Equal("false", hasError);
+			Assert.Contains("false", hasError, StringComparison.Ordinal);
 		});
 
 	private class TestExceptionMethods

src/Core/src/Handlers/HybridWebView/HybridWebViewHandler.cs

@@ -33,6 +33,7 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
 using Microsoft.Extensions.Logging;
+using System.Runtime.ExceptionServices;
 
 namespace Microsoft.Maui.Handlers
 {
@@ -278,7 +279,7 @@ private static DotNetInvokeResult CreateErrorResult(Exception ex)
 			}
 
 			// invoke the .NET method
-			var dotnetReturnValue = dotnetMethod.Invoke(jsInvokeTarget, invokeParamValues);
+			var dotnetReturnValue = GetDotNetMethodReturnValue(jsInvokeTarget, dotnetMethod, invokeParamValues);
 
 			if (dotnetReturnValue is null) // null result
 			{
@@ -303,6 +304,29 @@ private static DotNetInvokeResult CreateErrorResult(Exception ex)
 			return dotnetReturnValue; // regular result
 		}
 
+		private static object? GetDotNetMethodReturnValue(object jsInvokeTarget, MethodInfo dotnetMethod, object?[]? invokeParamValues)
+		{
+			try
+			{
+				// invoke the .NET method
+				return dotnetMethod.Invoke(jsInvokeTarget, invokeParamValues);
+			}
+			catch (TargetInvocationException tie) // unwrap while preserving original stack trace
+			{
+				if (tie.InnerException is not null)
+				{
+					// Rethrow the underlying exception without losing its original stack trace
+					ExceptionDispatchInfo.Capture(tie.InnerException).Throw();
+
+					// unreachable, but required for compiler flow analysis
+					throw;
+				}
+
+				// no inner exception; rethrow the TargetInvocationException itself preserving its stack
+				throw;
+			}
+		}
+
 		private sealed class JSInvokeMethodData
 		{
 			public string? MethodName { get; set; }