fix: NumberParseException instead of ArgumentOutOfRangeException on malformed RFC3966 phone-context ordering - #406
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…n on malformed RFC3966 phone-context ordering BuildNationalNumberForParsing assumed the "tel:" prefix, if present, always occurs before the ";phone-context=" marker. When it occurs after (e.g. ";phone-context=example.com;tel:1234"), indexOfPhoneContext - indexOfNationalNumber went negative and leaked an unchecked ArgumentOutOfRangeException from StringBuilder.Append(string, int, int) out of the public Parse API, instead of the documented NumberParseException. Found via code review of a separate change that narrowed a catch-all in PhoneNumbers.Extensions.PhoneNumber.TryParse to catch (NumberParseException) specifically — that narrowing was correct, but it stopped silently swallowing this pre-existing bug.
This was referenced Aug 24, 2026
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #406 +/- ##
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+ Coverage 77.26% 77.27% +0.01%
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Branches 1129 1130 +1
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This was referenced Aug 28, 2026
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This was referenced Sep 7, 2026
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Summary
BuildNationalNumberForParsingassumed the"tel:"prefix, if present anywhere in the input, always occurs before the";phone-context="marker. When it occurs after — e.g.";phone-context=example.com;tel:1234"—indexOfPhoneContext - indexOfNationalNumbergoes negative, andStringBuilder.Append(string, int, int)throws an uncheckedArgumentOutOfRangeExceptionstraight out of the publicPhoneNumberUtil.ParseAPI, instead of the documentedNumberParseException.Found via code review of #401 (narrowing
PhoneNumbers.Extensions.PhoneNumber.TryParse'scatchtocatch (NumberParseException)) — that narrowing is correct, but it stopped silently swallowing this pre-existing bug. It's reachable directly throughPhoneNumberUtil.Parsewith no dependency on #401, and is worse combined with #405's new[PhoneNumber]ValidationAttribute: aValidationAttribute.IsValidis conventionally expected to never throw on arbitrary/untrusted input, so this could crash model validation on a crafted string.Fix: guard the ordering assumption and throw
NumberParseException(NOT_A_NUMBER, ...)instead, matching the error this method already throws just above for other malformed phone-context input.Recommend merging this before/alongside #401 and #405.
Test plan
PhoneNumberUtil.GetInstance().Parse(";phone-context=example.com;tel:1234", null)threwArgumentOutOfRangeExceptionbefore this fix.TestFailedParseOnInvalidNumbers(VerifyFailure(";phone-context=example.com;tel:1234", RegionCode.ZZ, ErrorType.NOT_A_NUMBER)), alongside the other phone-context failure cases.dotnet build csharp --no-restore— 0 warnings/errorsdotnet test csharp/PhoneNumbers.slnx— 864 tests passed (net8.0 + net10.0)