Support Go 1.20 Unwrap() with a slice of errors

[ainar-g]

Summary

Go 1.20 added another way to unwrap errors, interface { Unwrap() []error }. As far as I can see, as of now Event.SetException doesn't support it.

sentry-go/interfaces.go

Lines 356 to 363 in cda691d

	switch previous := err.(type) {
	case interface{ Unwrap() error }:
	err = previous.Unwrap()
	case interface{ Cause() error }:
	err = previous.Cause()
	default:
	err = nil
	}

Motivation

Developers are updating to Go 1.20, as Go 1.19 is EOL now, and they will expect sentry-go to support the new interface and include all errors into the event data.

Additional Context

• https://pkg.go.dev/[email protected]
• errors: add support for wrapping multiple errors golang/go#53435

[tonyo]

Thanks, makes sense, added to the backlog.

[pierrre]

What should we do ? Get the first error in the slice ? Or explore the error's tree recursively (but the exceptions are a simple slice)

[ainar-g]

The Python API seems to already have a handler for a similar mechanism called ExceptionGroup:

https://github.com/getsentry/sentry-python/blob/641822dcf3cc90ee0c3e9726d4a5a979d4755c10/sentry_sdk/utils.py#L815-L832

Perhaps the same flatting algorithm could be used?

[pierrre]

I'm not very familiar with Python, sorry 😅
Is it adding recursively all errors to the array of exception ?

[ainar-g]

Neither do I really, heh. My point was more that there are similar idioms in other languages, and when the Sentry team starts working on the issue, they should probably follow the same principles as the APIs in those languages do.

And yes, it seems to add them one after the other, at least based on what I can read.

[pierrre]

This ?

// SetException appends the unwrapped errors to the event's exception list.
//
// maxErrorDepth is the maximum depth of the error chain we will look
// into while unwrapping the errors.
func (e *Event) SetException(exception error, maxErrorDepth int) {
	err := exception
	if err == nil {
		return
	}

	e.setException(err, maxErrorDepth)

	// Add a trace of the current stack to the most recent error in a chain if
	// it doesn't have a stack trace yet.
	// We only add to the most recent error to avoid duplication and because the
	// current stack is most likely unrelated to errors deeper in the chain.
	if e.Exception[0].Stacktrace == nil {
		e.Exception[0].Stacktrace = NewStacktrace()
	}

	// event.Exception should be sorted such that the most recent error is last.
	reverse(e.Exception)
}

func (e *Event) setException(err error, maxErrorDepth int) {
	for i := 0; i < maxErrorDepth && err != nil; i++ {
		e.Exception = append(e.Exception, Exception{
			Value:      err.Error(),
			Type:       reflect.TypeOf(err).String(),
			Stacktrace: ExtractStacktrace(err),
		})
		switch previous := err.(type) {
		case interface{ Unwrap() error }:
			err = previous.Unwrap()
		case interface{ Unwrap() []error }:
			errs := previous.Unwrap()
			for _, errw := range errs {
				e.setException(errw, maxErrorDepth-i-1)
			}
			err = nil
		case interface{ Cause() error }:
			err = previous.Cause()
		default:
			err = nil
		}
	}
}

[greywolve]

Seems like supporting these kind of error groups is a newish feature, see: getsentry/sentry#37716

[greywolve]

Also the RFC: https://github.com/getsentry/rfcs/blob/main/text/0079-exception-groups.md

[greywolve]

Here's the sentry-javascript implementation, so this change will be a bit more involved.

[proost]

hello! any progress? Also joinError does not get proper stack trace too.

[cleptric]

No progress, still in our backlog.