[wasm][debugger] Detect exception/error when calling runtime_invoke

src/mono/mono/mini/mini-wasm-debugger.c

@@ -72,6 +72,7 @@ G_END_DECLS
 static void describe_object_properties_for_klass (void *obj, MonoClass *klass, gboolean isAsyncLocalThis, int gpflags);
 static void handle_exception (MonoException *exc, MonoContext *throw_ctx, MonoContext *catch_ctx, StackFrameInfo *catch_frame);
 static void assembly_loaded (MonoProfiler *prof, MonoAssembly *assembly);
+static MonoObject* mono_runtime_try_invoke_internal (MonoMethod *method, void *obj, void **params, MonoObject **exc, MonoError* error);
 
 //FIXME move all of those fields to the profiler object
 static gboolean debugger_enabled;
@@ -83,6 +84,7 @@ static GHashTable *objrefs;
 static GHashTable *obj_to_objref;
 static int objref_id = 0;
 static int pause_on_exc = EXCEPTION_MODE_NONE;
+static MonoObject* exception_on_runtime_invoke = NULL;
 
 static const char*
 all_getters_allowed_class_names[] = {
@@ -314,7 +316,7 @@ get_this_async_id (DbgEngineStackFrame *frame)
 		return 0;
 	}
 
-	obj = mono_runtime_try_invoke (method, builder, NULL, &ex, error);
+	obj = mono_runtime_try_invoke_internal (method, builder, NULL, &ex, error);
 	mono_error_assert_ok (error);
 
 	return get_object_id (obj);
@@ -552,6 +554,9 @@ handle_exception (MonoException *exc, MonoContext *throw_ctx, MonoContext *catch
 {
 	ERROR_DECL (error);
 	PRINT_DEBUG_MSG (1, "handle exception - %d - %p - %p - %p\n", pause_on_exc, exc, throw_ctx, catch_ctx);
+
+    //normal mono_runtime_try_invoke does not capture the exception and this is a temporary workaround.
+	exception_on_runtime_invoke = (MonoObject*)exc;
 
 	if (pause_on_exc == EXCEPTION_MODE_NONE)
 		return;
@@ -807,7 +812,7 @@ invoke_to_string (const char *class_name, MonoClass *klass, gpointer addr)
 		if (!method)
 			return NULL;
 
-		MonoString *mstr = (MonoString*) mono_runtime_try_invoke (method, addr , NULL, &exc, error);
+		MonoString *mstr = (MonoString*) mono_runtime_try_invoke_internal (method, addr , NULL, &exc, error);
 		if (exc || !is_ok (error)) {
 			PRINT_DEBUG_MSG (1, "Failed to invoke ToString for %s\n", class_name);
 			return NULL;
@@ -1190,17 +1195,36 @@ invoke_and_describe_getter_value (MonoObject *obj, MonoProperty *p)
 
 	MonoMethodSignature *sig = mono_method_signature_internal (p->get);
 
-	res = mono_runtime_try_invoke (p->get, obj, NULL, &exc, error);
+	res = mono_runtime_try_invoke_internal (p->get, obj, NULL, &exc, error);
 	if (!is_ok (error) && exc == NULL)
-		exc = (MonoObject*) mono_error_convert_to_exception (error);
+		exc = (MonoObject *) mono_error_convert_to_exception (error);
 	if (exc)
-		return describe_value (mono_get_object_type (), &exc, GPFLAG_EXPAND_VALUETYPES);
+	{
+		const char *class_name = mono_class_full_name (mono_object_class (exc));
+		ERROR_DECL (local_error);
+		char *str = mono_string_to_utf8_checked_internal (((MonoException*)exc)->message, local_error);
+		mono_error_assert_ok (local_error); /* FIXME report error */
+		char *msg = g_strdup_printf("%s: %s", class_name, str);
+		mono_wasm_add_typed_value ("string", msg, 0);
+		g_free (msg);
+		return TRUE;
+	}
 	else if (!res || !m_class_is_valuetype (mono_object_class (res)))
 		return describe_value (sig->ret, &res, GPFLAG_EXPAND_VALUETYPES);
 	else
 		return describe_value (sig->ret, mono_object_unbox_internal (res), GPFLAG_EXPAND_VALUETYPES);
 }
 
+static MonoObject* mono_runtime_try_invoke_internal (MonoMethod *method, void *obj, void **params, MonoObject **exc, MonoError* error)
+{
+	exception_on_runtime_invoke = NULL;
+	MonoObject* res = mono_runtime_try_invoke (method, obj, params, exc, error);
+	if (exception_on_runtime_invoke != NULL)
+		*exc = exception_on_runtime_invoke;
+	exception_on_runtime_invoke = NULL;
+	return res;
+}
+
 static void
 describe_object_properties_for_klass (void *obj, MonoClass *klass, gboolean isAsyncLocalThis, int gpflags)
 {

src/mono/wasm/debugger/DebuggerTestSuite/EvaluateOnCallFrameTests.cs

@@ -465,6 +465,17 @@ await EvaluateOnCallFrameFail(id,
                    ("this.NullIfAIsNotZero.foo", "ReferenceError"));
            });
 
+        [Fact]
+        public async Task EvaluatePropertyThatThrows()
+        => await CheckInspectLocalsAtBreakpointSite(
+            "DebuggerTests.EvaluateTestsClassWithProperties", "InstanceMethod", /*line_offset*/1, "InstanceMethod",
+            $"window.setTimeout(function() {{ invoke_static_method_async('[debugger-test] DebuggerTests.EvaluateTestsClassWithProperties:run');}}, 1);",
+            wait_for_event_fn: async (pause_location) =>
+            {
+                var id = pause_location["callFrames"][0]["callFrameId"].Value<string>();
+                await EvaluateOnCallFrameAndCheck(id, ("this.PropertyThrowException", TString("System.Exception: error")));
+            });
+
         async Task EvaluateOnCallFrameAndCheck(string call_frame_id, params (string expression, JObject expected)[] args)
         {
             foreach (var arg in args)

src/mono/wasm/debugger/tests/debugger-test/debugger-evaluate-test.cs

@@ -76,6 +76,7 @@ public class EvaluateTestsClassWithProperties
         public DateTime dateTime;
         public DateTime DTProp => dateTime.AddMinutes(10);
         public int IntProp => a + 5;
+        public string PropertyThrowException => throw new Exception("error");
         public string SetOnlyProp { set { a = value.Length; } }
         public EvaluateTestsClassWithProperties NullIfAIsNotZero => a != 1908712 ? null : new EvaluateTestsClassWithProperties(0);
         public EvaluateTestsClassWithProperties NewInstance => new EvaluateTestsClassWithProperties(3);