I am making a json unmarshalling error handling function in Go:
import "github.com/pkg/errors"
func parseJSONError(err error) {
var uterr json.UnmarshalTypeError
if errors.As(err, &uterr) {
//...
return
}
var serr json.SyntaxError
if errors.As(err, &serr) {
//...
return
}
}
But there is a panic in errors.As()
: panic: errors: *target must be interface or implement error
.
What is target we can learn from the github.com/pkg/errors documentation:
func As(err error, target interface{}) bool
The problem is that both json.UnmarshalTypeError
and json.SyntaxError
actually implement the error
interface. We can learn it from the encoding/json documentation. So I do not have any idea what I am doing wrong. Even explicit casting uterr
and serr
to the interface{}
does not save the situation.
The panic occurs in both github.com/pkg/errors
and standard errors
packages.
CodePudding user response:
json.UnmarshalTypeError
does not implementerror
.*json.UnmarshalTypeError
does (becauseError() string
has pointer receiver)errors.As
wants a pointer to what implementerror
, so you need**json.UnmarshalTypeError
Change to:
uterr := &json.UnmarshalTypeError{}
if errors.As(err, &uterr) {
// ...
return
}