pkg/error cause inspector

causer.go

type errTwo struct{}

func (errTwo) Error() string {
	return "errTwo"
}

type errOne struct{}

func (errOne) Error() string {
	return "errOne"
}
func (errOne) BadArguments() string {
	return "bad bad arguments"
}
func (errOne) Behave() {
}
func main() {
	errOne := errors.Wrap(errOne{}, "first error message")
	errTwo := errors.Wrap(errOne, "second error message")
	errThree := errors.Wrap(errTwo, "third error message")
	fmt.Println(inspectCause(errThree, func(err error) (ok bool) {
		_, ok = err.(behaver)
		return
	}))
}

type behaver interface {
	Behave()
}

func inspectCause(err error, inspect func(err error) bool) bool {
	type causer interface {
		Cause() error
	}

	var hasBehavior bool
	for err != nil {
		hasBehavior = inspect(err)
		cause, ok := err.(causer)
		if !ok {
			break
		}
		err = cause.Cause()
	}
	return hasBehavior
}

Inspired By: Assert errors for behaviour, not type
ref: https://dave.cheney.net/2016/04/27/dont-just-check-errors-handle-them-gracefully

It walks the stack-trace from pkg/error to see if it exhibits certain behavior for special handling.