[draft] fix(web): don't create runZoneGuarded on web if it already exists

flutter/lib/src/sentry_flutter.dart

@@ -72,15 +72,23 @@
  final platformDispatcher = PlatformDispatcher.instance;
  final wrapper = PlatformDispatcherWrapper(platformDispatcher);
 
- // Flutter Web don't capture [Future] errors if using [PlatformDispatcher.onError] and not
+ // Flutter Web doesn't capture [Future] errors if using [PlatformDispatcher.onError] and not
  // the [runZonedGuarded].
  // likely due to https://github.com/flutter/flutter/issues/100277
- final isOnErrorSupported = flutterOptions.platformChecker.isWeb
- ? false
- : wrapper.isOnErrorSupported(flutterOptions);
+ final bool isOnErrorSupported = !flutterOptions.platformChecker.isWeb &&
+ wrapper.isOnErrorSupported(flutterOptions);
 
- final runZonedGuardedOnError = flutterOptions.platformChecker.isWeb
- ? _createRunZonedGuardedOnError()
+ final bool customZoneExists = Zone.current != Zone.root;
+
+ // If onError is not supported and no custom zone exists, use runZonedGuarded to capture errors.
+ final bool useRunZonedGuarded = !isOnErrorSupported && !customZoneExists;
+
+ // Retrieve the onError callback set by the user if a custom zone exists.
+ final RunZonedGuardedOnError? additionalOnError =
+ customZoneExists ? Zone.current.handleUncaughtError : null;
+
+ RunZonedGuardedOnError? runZonedGuardedOnError = useRunZonedGuarded
+ ? _createRunZonedGuardedOnError(additionalOnError: additionalOnError)
  : null;
 
  // first step is to install the native integration and set default values,
@@ -104,7 +112,7 @@
  // ignore: invalid_use_of_internal_member
  options: flutterOptions,
  // ignore: invalid_use_of_internal_member
- callAppRunnerInRunZonedGuarded: !isOnErrorSupported,
+ callAppRunnerInRunZonedGuarded: useRunZonedGuarded,
  // ignore: invalid_use_of_internal_member
  runZonedGuardedOnError: runZonedGuardedOnError,
  );
@@ -199,13 +207,19 @@
  return integrations;
  }
 
- static RunZonedGuardedOnError _createRunZonedGuardedOnError() {
+ static RunZonedGuardedOnError _createRunZonedGuardedOnError({
+ RunZonedGuardedOnError? additionalOnError,
+ }) {
  return (Object error, StackTrace stackTrace) async {
  final errorDetails = FlutterErrorDetails(
  exception: error,
  stack: stackTrace,
  );
  FlutterError.dumpErrorToConsole(errorDetails, forceReport: true);
+
+ if (additionalOnError != null) {
+ additionalOnError(error, stackTrace);
+ }
  };
  }