Area code information lost for all MX numbers

Author: twcclegg

csharp/PhoneNumbers.Test/TestPhoneNumberUtil.cs

@@ -296,6 +296,9 @@ public void TestGetLengthOfGeographicalAreaCode()
             // Italian numbers - there is no national prefix, but it still has an area code.
             Assert.Equal(2, phoneUtil.GetLengthOfGeographicalAreaCode(ITNumber));
 
+            // Mexico numbers - there is no national prefix, but it still has an area code.
+            Assert.Equal(2, phoneUtil.GetLengthOfGeographicalAreaCode(MXNumber1));
+
             // Google Singapore. Singapore has no area code and no national prefix.
             Assert.Equal(0, phoneUtil.GetLengthOfGeographicalAreaCode(SGNumber));
 

csharp/PhoneNumbers/PhoneNumberUtil.cs

@@ -73,6 +73,10 @@ public partial class PhoneNumberUtil
         private static bool IsGeoMobileCountryWithoutMobileAreaCode(int countryCallingCode)
             => countryCallingCode is 86; // China
 
+        // Set of country codes that doesn't have national prefix, but it has area codes.
+        private static bool IsCountryWithoutNationalPrefixWithAreaCodes(int countryCallingCode)
+            => countryCallingCode is 52; // Mexico
+
         // Set of country calling codes that have geographically assigned mobile numbers. This may not be
         // complete; we add calling codes case by case, as we find geographical mobile numbers or hear
         // from user reports. Note that countries like the US, where we can't distinguish between
@@ -662,14 +666,18 @@ public int GetLengthOfGeographicalAreaCode(PhoneNumber number)
             var regionCode = GetRegionCodeForNumber(number);
             if (!IsValidRegionCode(regionCode))
                 return 0;
+
+            var type = GetNumberType(number);
+            var countryCallingCode = number.CountryCode;
             var metadata = GetMetadataForRegion(regionCode);
             // If a country doesn't use a national prefix, and this number doesn't have an Italian leading
             // zero, we assume it is a closed dialling plan with no area codes.
-            if (!metadata.HasNationalPrefix && !number.HasNumberOfLeadingZeros)
+            // Note:this is our general assumption, but there are exceptions which are tracked in
+            // COUNTRIES_WITHOUT_NATIONAL_PREFIX_WITH_AREA_CODES.
+            if (!metadata.HasNationalPrefix && !number.HasNumberOfLeadingZeros &&
+                    !IsCountryWithoutNationalPrefixWithAreaCodes(countryCallingCode))
                 return 0;
 
-            var type = GetNumberType(number);
-            var countryCallingCode = number.CountryCode;
             if (type == PhoneNumberType.MOBILE
                 // Note this is a rough heuristic; it doesn't cover Indonesia well, for example, where area
                 // codes are present for some mobile phones but not for others. We have no better way of