AnnaShaleva
commented
7 months ago Ping to this issue, because NNS wrapper (#3291) uses getRecord NNS method that returns Null stackitem in case of missing record of the specified type. And neither unwrap.UTF8String nor unwrap.Bytes can handle Null stackitem. As a result in the described case we've got an error from the NNS wrapper side on attempt to unwrap Null into Go's string while NNS itself doesn't return any error.
IMO, this behaviour of NNS wrapper is not correct and it will be fixed by this issue. We likely should return an empty string and no error form NNS wrapper in the described case. So something like the following will be useful, but we need to evaluate the usages of unwrap.Bytes and similar methods. Maybe we can directly modify unwrap.Bytes and etc. to properly handle Null.
+// Bytes expects correct execution (HALT state) with a single stack item
+// returned. A slice of bytes is extracted from this item and returned.
+func BytesOrNull(r *result.Invoke, err error) ([]byte, error) {
+ itm, err := Item(r, err)
+ if err != nil {
+ return nil, err
+ }
+ if itm.Equals(stackitem.Null{}) {
+ return nil, nil
+ }
+ return itm.TryBytes()
+}
+
+// UTF8String expects correct execution (HALT state) with a single stack item
+// returned. A string is extracted from this item and checked for UTF-8
+// correctness, valid strings are then returned.
+func UTF8StringOrNull(r *result.Invoke, err error) (string, error) {
+ b, err := BytesOrNull(r, err)
+ if err != nil {
+ return "", err
+ }
+ if b == nil {
+ return "", nil
+ }
+ if !utf8.Valid(b) {
+ return "", errors.New("not a UTF-8 string")
+ }
+ return string(b), nil
+}
+
@roman-khimov, what do you think?
@AliceInHunterland, this issue is related to error returned from recordData, err := nnsReader.GetRecord(domainName, recordType)
roman-khimov
cthulhu-rider
It's true that we can have Null in many cases. We can have
nilin Go at the same time. Maybe it's OK to return it.