[vm] Use toString when generating stacktrace in isolate error handler

Closes #50438

TEST=tests/lib/isolate/handle_error_stacktrace_test, tests/lib/isolate/handle_exiting_to_string_error_test, tests/lib/isolate/handle_throwing_to_string_error_test

Change-Id: I098153ecd65360aa724e25fc52e25368ca27ffe7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/277341
Reviewed-by: Alexander Aprelev <[email protected]>
Reviewed-by: Derek Xu <[email protected]>

Author: abitofevrything

runtime/vm/isolate.cc

@@ -1596,15 +1596,25 @@ MessageHandler::MessageStatus IsolateMessageHandler::ProcessUnhandledException(
     } else {
       const Object& exception_str =
           Object::Handle(zone, DartLibraryCalls::ToString(exception));
-      if (!exception_str.IsString()) {
+      if (exception_str.IsUnwindError()) {
+        return StoreError(T, UnwindError::Cast(exception_str));
+      } else if (!exception_str.IsString()) {
         exception_cstr = exception.ToCString();
       } else {
         exception_cstr = exception_str.ToCString();
       }
     }
 
     const Instance& stacktrace = Instance::Handle(zone, uhe.stacktrace());
-    stacktrace_cstr = stacktrace.ToCString();
+    const Object& stacktrace_str =
+        Object::Handle(zone, DartLibraryCalls::ToString(stacktrace));
+    if (stacktrace_str.IsUnwindError()) {
+      return StoreError(T, UnwindError::Cast(stacktrace_str));
+    } else if (!stacktrace_str.IsString()) {
+      stacktrace_cstr = stacktrace.ToCString();
+    } else {
+      stacktrace_cstr = stacktrace_str.ToCString();
+    }
   } else {
     exception_cstr = result.ToErrorCString();
   }

tests/lib/isolate/handle_error_stacktrace_test.dart

@@ -0,0 +1,41 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library handle_error_stacktrace_test;
+
+import "dart:isolate";
+
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+
+const errorValue = "TEST_ERROR";
+const stackTraceValue = "TEST_STACKTRACE";
+
+void isolateMain() {
+  Error.throwWithStackTrace(errorValue, StackTrace.fromString(stackTraceValue));
+}
+
+void main() async {
+  asyncStart();
+
+  var receivedErrors = 0;
+  final errorPort = ReceivePort();
+  errorPort.listen((errorAndStack) {
+    Expect.listEquals([errorValue, stackTraceValue], errorAndStack);
+    receivedErrors++;
+
+    if (receivedErrors == 2) {
+      errorPort.close();
+      asyncEnd();
+    }
+  });
+
+  Isolate.spawn((_) => isolateMain(), null, onError: errorPort.sendPort);
+  Isolate.spawn(
+    (_) => isolateMain(),
+    null,
+    onError: errorPort.sendPort,
+    errorsAreFatal: false,
+  );
+}

tests/lib/isolate/handle_exiting_to_string_error_test.dart

@@ -0,0 +1,45 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library handle_throwing_to_string_error_test;
+
+import "dart:async";
+import "dart:isolate";
+
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+
+class ExitingToStringError {
+  @override
+  String toString() => Isolate.exit();
+}
+
+void isolateMain() {
+  throw ExitingToStringError();
+}
+
+void main() async {
+  asyncStart();
+  final errorPort = ReceivePort();
+  final exitPort = ReceivePort();
+  Isolate.spawn(
+    (_) => isolateMain(),
+    null,
+    onError: errorPort.sendPort,
+    onExit: exitPort.sendPort,
+  );
+
+  exitPort.listen((_) {
+    exitPort.close();
+
+    // Give the (hopefully inexistent) error message time to arrive.
+    Timer(Duration(seconds: 1), () {
+      errorPort.close();
+    });
+  });
+
+  Expect.isTrue(await errorPort.isEmpty);
+
+  asyncEnd();
+}

tests/lib/isolate/handle_throwing_to_string_error_test.dart

@@ -0,0 +1,39 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library handle_throwing_to_string_error_test;
+
+import "dart:isolate";
+
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+
+class ThrowingToStringError {
+  @override
+  String toString() => throw ThrowingToStringError();
+}
+
+class ThrowingToStringStackTrace implements StackTrace {
+  @override
+  String toString() => throw ThrowingToStringStackTrace();
+}
+
+void isolateMain() {
+  Error.throwWithStackTrace(
+    ThrowingToStringError(),
+    ThrowingToStringStackTrace(),
+  );
+}
+
+void main() async {
+  asyncStart();
+  final errorPort = ReceivePort();
+  Isolate.spawn((_) => isolateMain(), null, onError: errorPort.sendPort);
+  var errorAndStack = await errorPort.first as List<Object?>;
+  Expect.listEquals([
+    "Instance of 'ThrowingToStringError'",
+    "Instance of 'ThrowingToStringStackTrace'",
+  ], errorAndStack);
+  asyncEnd();
+}