flutter error integration calls original handler with stale error

[ardera]

Platform

Flutter Wasm, Flutter Web, Flutter Desktop Linux, Flutter Desktop Windows, Flutter Mobile Android, Flutter Mobile iOS

Obfuscation

Enabled

Debug Info

Enabled

Doctor

flutter version: 3.32.5

Version

8.14.2

Steps to Reproduce

It's a race condition and thus unreliable to reproduce, but the root cause is here:

sentry-dart/packages/flutter/lib/src/integrations/flutter_error_integration.dart

Lines 91 to 107 in 05da225

	await hub.captureEvent(event, stackTrace: stackTrace, hint: hint);
	// we don't call Zone.current.handleUncaughtError because we'd like
	// to set a specific mechanism for FlutterError.onError.
	} else {
	options.log(
	SentryLevel.debug,
	'Error not captured due to [FlutterErrorDetails.silent], '
	'Enable [SentryFlutterOptions.reportSilentFlutterErrors] '
	'if you wish to capture silent errors',
	);
	}
	// Call original handler, regardless of `errorDetails.silent` or
	// `reportSilentFlutterErrors`. This ensures, that we don't swallow
	// messages.
	if (_defaultOnError != null) {
	_defaultOnError!(errorDetails);
	}

The sentry error integration calls the original error handler with the reported error, but that might only happen after an async await, and apparently some parts of the flutter error can't be used across async gaps.

For example, the flutter widget inspector error handler will serialize the diagnostics node, with all its render objects, etc:
https://github.com/flutter/flutter/blob/7438e5491588fdb0852161fd2b8df46b32515d37/packages/flutter/lib/src/widgets/widget_inspector.dart#L1008-L1032

And that might fail if the render objects are already diposed. E.g. calling debugDescribeChildren on a RenderParagraph (Text widget) throws an error for me. (See actual result)

Expected Result

No error.

Actual Result

This is the call stack when the error happens: (The exception is Null check operator used on a null value)

RenderParagraph.text (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\rendering\paragraph.dart:391)
RenderParagraph.debugDescribeChildren (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\rendering\paragraph.dart:1398)
DiagnosticableTreeNode.getChildren (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:2968)
DiagnosticsNode.toJsonMap.<anonymous closure> (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1644)
DiagnosticsNode.toJsonMap (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1670)
DiagnosticsNode.toJsonList.<anonymous closure> (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1717)
MappedListIterable.elementAt (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\internal\iterable.dart:442)
ListIterator.moveNext (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\internal\iterable.dart:371)
new _GrowableList._ofEfficientLengthIterable (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\_internal\vm\lib\growable_array.dart:194)
new _GrowableList.of (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\_internal\vm\lib\growable_array.dart:154)
new List.of (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\_internal\vm\lib\array_patch.dart:40)
ListIterable.toList (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\internal\iterable.dart:224)
DiagnosticsNode.toJsonList (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1718)
DiagnosticsNode.toJsonMap.<anonymous closure> (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1667)
DiagnosticsNode.toJsonMap (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1670)
DiagnosticsNode.toJsonList.<anonymous closure> (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1717)
MappedListIterable.elementAt (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\internal\iterable.dart:442)
ListIterator.moveNext (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\internal\iterable.dart:371)
new _GrowableList._ofEfficientLengthIterable (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\_internal\vm\lib\growable_array.dart:194)
new _GrowableList.of (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\_internal\vm\lib\growable_array.dart:154)
new List.of (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\_internal\vm\lib\array_patch.dart:40)
ListIterable.toList (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\internal\iterable.dart:224)
DiagnosticsNode.toJsonList (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1718)
DiagnosticsNode.toJsonMap.<anonymous closure> (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1667)
DiagnosticsNode.toJsonMap (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1670)
DiagnosticsNode.toJsonList.<anonymous closure> (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1717)
MappedListIterable.elementAt (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\internal\iterable.dart:442)
ListIterator.moveNext (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\internal\iterable.dart:371)
new _GrowableList._ofEfficientLengthIterable (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\_internal\vm\lib\growable_array.dart:194)
new _GrowableList.of (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\_internal\vm\lib\growable_array.dart:154)
new List.of (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\_internal\vm\lib\array_patch.dart:40)
ListIterable.toList (c:\Users\HannesWinkler\devel\flutter\bin\cache\pkg\sky_engine\lib\internal\iterable.dart:224)
DiagnosticsNode.toJsonList (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1718)
DiagnosticsNode.toJsonMap.<anonymous closure> (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1661)
DiagnosticsNode.toJsonMap (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\foundation\diagnostics.dart:1670)
WidgetInspectorService._nodeToJson (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\widgets\widget_inspector.dart:1774)
WidgetInspectorService._reportStructuredError (c:\Users\HannesWinkler\devel\flutter\packages\flutter\lib\src\widgets\widget_inspector.dart:1010)
FlutterErrorIntegration.call.<anonymous closure> (d:\.pub-cache\hosted\pub.dev\sentry_flutter-8.14.2\lib\src\integrations\flutter_error_integration.dart:106)
<asynchronous gap> (Unknown Source:0)

Are you willing to submit a PR?

None

[linear]

DART-204 flutter error integration calls original handler with stale error

[kahest]

Thanks @ardera for the detailed report, we'll investigate. In the mean time, do you have more info on "some parts of the flutter error can't be used across async gaps"?

[buenaflor]

it looks like this can be improved, we don't need to actually await here so we can potentially remove the async

[ardera]

@kahest Sure, the FlutterErrorDetails can have a diagnostics node: https://api.flutter.dev/flutter/foundation/FlutterErrorDetails/toDiagnosticsNode.html

That diagnostics node could be a RenderObject. It's possible that this render object gets disposed when you're doing an async await in the error handler. And after that, doing anything with the diagnostics node might throw errors, like it did in my case.