Incorrect country detection for phone numbers with shared prefixes (+1, +7)

[nikolaiovchinnikov]

Hi!

When detecting the country based on the phone prefix, there seems to be an issue — for example, numbers from the US and Canada, or Russia and Kazakhstan, are not always detected correctly.

I suspect the problem might be related to this line:

phone_numbers_parser/lib/src/metadata/metadata_finder.dart

Line 115 in e4fb46e

if (leadingDigits != null && nationalNumber.startsWith(leadingDigits)) {

Additionally, there seems to be an issue in the regular expression here:

phone_numbers_parser/lib/src/metadata/generated/metadata_by_iso_code.dart

Line 977 in e4fb46e

leadingDigits: r"33|7",

It doesn’t correctly match numbers like +7705, which should be identified as Kazakhstan, but they might be misclassified or rejected.

[cedvdb]

Which phone number are you using ? Could it be that it is a valid russian number for this line ?

phone_numbers_parser/lib/src/metadata/metadata_finder.dart

Line 106 in e4fb46e

final isValidForIso =

Could you check that it is indeed the case ?

I believe the line you provided would return kazakstan as it has a leading digit of 7 (which is the second 7 in +77). I believe the logic should be changed somewhat here so that if there are elements in potentialMatches that regex match the start of the national number there, the list should be reduced to only those elements.

So something like

  static PhoneMetadata _getBestMatch(
    String nationalNumber,
    List<PhoneMetadata> potentialFits,
  ) {
     if (potentialFits.length == 1) return potentialFits[0];
     
     // otherwise if there are elements in `potentialMatches` that  have leadingDigits that
     // regex match the start of the national number there, the list should be reduced to only those elements.
     final reducedPotentialFits = ... // TODO
     if (reducedPotentialFits.length == 1) return reducedPotentialFits[0];

         // if the phone number is valid for a metadata return that metadata
    for (var fit in potentialFits) {
      final isValidForIso =
          Validator.validateWithPattern(fit.isoCode, nationalNumber);
      if (isValidForIso) {
        return fit;
      }
    }

    return potentialFits.firstWhere(
      (fit) => fit.isMainCountryForDialCode,
      orElse: () => potentialFits[0],
    );
  }

Please tell me if I'm off the mark here

[nikolaiovchinnikov]

Hi!

Thanks a lot for the detailed explanation — it all makes perfect sense.
I think the issue is that leadingDigits is treated as a plain string instead of a regular expression. So this line:

if (leadingDigits != null && nationalNumber.startsWith(leadingDigits))

doesn’t work correctly for patterns like r"33|7".

It’s enough to just change it to:

if (leadingDigits != null && nationalNumber.startsWith(RegExp(leadingDigits))) {

— and things should start working properly, since startsWith(RegExp) correctly interprets the pattern.
https://api.dart.dev/dart-core/String/startsWith.html

That said, I also like your suggestion to reverse the logic: first filter potentialFits by leadingDigits match, then validate the number, and finally fall back to mainCountryForDialCode. That approach makes the logic cleaner and more predictable, especially in tricky cases like US/Canada or Russia/Kazakhstan.

Thanks again for your response and a great idea!

Sorry if anything in my message is unclear — I have some difficulties with English.

[nikolaiovchinnikov]

It would be great to add the following countries and territories to the dictionary along with their phone codes (many of them are Caribbean or U.S. territories): American Samoa (+1-684), Guam (+1-671), Anguilla (+1-264), Jamaica (+1-876, +1-658), Antigua and Barbuda (+1-268), Montserrat (+1-664), Bahamas (+1-242), Northern Mariana Islands (+1-670), Barbados (+1-246), Puerto Rico (+1-787, +1-939), Bermuda (+1-441), Saint Kitts and Nevis (+1-869), British Virgin Islands (+1-284), Saint Lucia (+1-758), Cayman Islands (+1-345), Saint Vincent and the Grenadines (+1-784), Dominica (+1-767), Sint Maarten (+1-721), Dominican Republic (+1-809, +1-829, +1-849), Trinidad and Tobago (+1-868), Grenada (+1-473), Turks and Caicos Islands (+1-649).
Source: Worldometer

[cedvdb]

Can you submit a PR for the above suggestions ?

It would be great to add the following countries and territories to the dictionary along with their phone code

The metadata is taken from the libphonenumber repository, so it has to be updated there first