Validation reason is incorrectly called FAILED_CUSTOM_VALIDATION

[tbatchlear]

Is this bug report about an incorrectly validated email address?

• [ ] Yes
• [ X ] No

If no, please describe the bug

When validating an email address in the following manner, the validation failure message is incorrect:

String invalidDomain = "my.email@example.org";
var result  = javaJMail.validator().requireOnlyTopLevelDomain(TopLevelDomain.DOT_COM).validate(invalidDomain);

This returns a FailureReason.FAILED_CUSTOM_VALIDATION. There should be a failure reason to match the validation here done on this domain. Perhaps a FailureReason.INVALID_TOP_LEVEL_DONAIN would be appropriate.

Additionally, if passing my.email@example to the above validation, it still returns the FAILED_CUSTOM_VALIDATION reason. However, there is already an existing "MISSING_TOP_LEVEL_DOMAIN" that should be used here instead when used in conjunction with the requireOnlyTopLevelDomain(), as this implies that a TLD is required.

Finally, as a side thought on this, it would be nice to be able to add a custom failure reason, perhaps along with the custom validator?

public EmailValidator withRule(Predicate<Email> rule, String failureReason);

Then, instead of these predicates being stored as a Set, they could be stored as a Map along with their failure reason.

[RohanNagar]

Hi @tbatchlear, thank you so much for opening this issue!

You are correct that the failure reasons when adding additional rules are not very great at the moment. We also have issue #140 open to address this.

I've actually already started the work for these improvements, including:

1. Better failure reasons for built-in rules like requireOnlyTopLevelDomain
2. The option to add your own custom FailureReason when adding a custom rule

I'll keep this open as it is a great motivator when multiple people are requesting a feature 🙂. I hope to have this ready for you soon!