PhoneInputFormatter incorrectly converts Brazilian area code 83 to 73

[MarcosPereira1]

Bug Description

The PhoneInputFormatter has a bug where it incorrectly converts the Brazilian area code 83 (Paraíba state) to 73 (Bahia state) during phone number formatting.

Steps to Reproduce

1. Create a PhoneInputFormatter with Brazilian settings:

   final formatter = PhoneInputFormatter(
     allowEndlessPhone: false,
     defaultCountryCode: 'BR',
   );

2. Try to format a phone number starting with area code 83:

   final result = formatter.formatEditUpdate(
     TextEditingValue(),
     TextEditingValue(text: '83987654321'),
   );

3. Observe the result

Expected Behavior

• Input: 83987654321
• Expected output: (83) 98765-4321

Actual Behavior

• Input: 83987654321
• Actual output: (73) 98765-4321 ❌

The area code is incorrectly changed from 83 to 73.

bug.mp4

Impact

This affects users from Paraíba state (Brazil) who cannot correctly input their phone numbers. Area code 83 is a valid Brazilian area code assigned to Paraíba state by ANATEL (Brazilian telecommunications agency).

Environment

• Package: flutter_multi_formatter
• Versions tested: 2.10.0, 2.12.0, 2.13.10 (bug exists in all tested versions)
• Flutter: 3.24.3
• Dart: 3.5.3
• Platform: iOS/Android

Additional Context

• Area code 83 is officially assigned to Paraíba state, Brazil
• Area code 73 is assigned to Bahia state, Brazil
• This appears to be a mapping issue within the library's phone formatting logic
• The bug occurs both during step-by-step typing and when formatting complete numbers

Workaround

We've implemented a temporary wrapper that detects and fixes this specific case:

class CustomPhoneInputFormatter extends TextInputFormatter {
  final PhoneInputFormatter _baseFormatter;

  // ... constructor

  @override
  TextEditingValue formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue) {
    final baseResult = _baseFormatter.formatEditUpdate(oldValue, newValue);
    
    // Fix the specific bug: DDD 83 being changed to 73
    if (_shouldFixDDD83(newValue.text, baseResult.text)) {
      final correctedText = baseResult.text.replaceFirst('(73', '(83');
      return TextEditingValue(
        text: correctedText,
        selection: TextSelection.collapsed(offset: correctedText.length),
      );
    }
    return baseResult;
  }

  bool _shouldFixDDD83(String originalText, String formattedText) {
    final original = originalText.replaceAll(RegExp(r'[^\d]'), '');
    final formatted = formattedText.replaceAll(RegExp(r'[^\d]'), '');
    return original.startsWith('83') && formatted.startsWith('73');
  }
}

Test Case

void main() {
  test('PhoneInputFormatter should preserve area code 83', () {
    final formatter = PhoneInputFormatter(
      allowEndlessPhone: false,
      defaultCountryCode: 'BR',
    );

    final result = formatter.formatEditUpdate(
      TextEditingValue(),
      TextEditingValue(text: '83987654321'),
    );

    expect(result.text, contains('83')); // Should contain 83
    expect(result.text, isNot(contains('73'))); // Should NOT contain 73
  });
}

Would appreciate a fix for this issue as it affects Brazilian users from Paraíba state.