There should be specialized normalizers for E-Mails

[MovGP0]

Is your feature request related to a problem? Please describe.

Given I have an E-Mail address that includes unicode characters. When its normalized in the database using the UpperInvariantLookupNormalizer, those unicode characters are not properly escaped into Punycode using the System.Globalization.IdnMapping class.

When registering a custom normalizer, it will apply to email addresses and user names, even in use cases when the user name is not an email address.

Describe the solution you'd like

I propose to have specialized versions of ILookupNormalizer for e-mail addresses and user names:

public interface IUserNameLookupNormalizer : ILookupNormalizer {}
public interface IEmailLookupNormalizer : ILookupNormalizer {}

as well as appropriate default implementations that remove diacritic symbols, or escape punycode respectively.

Describe alternatives you've considered

The current workaround is to implement custom IUserEmailStore<TUser>, UserManager<User>, and RoleManager<Role> derived classes and overwrite the methods which use the normalized username or the normalized email address. One can that implement the interfaces above and provide the normalizers using Dependency Injection.

[MovGP0]

btw: the class Microsoft.AspNetCore.Identity.UpperInvariantLookupNormalizer should probably be sealed, since the implementation is trivial.

[blowdart]

Can I assume you mean punycode in the domain name, rather than the account within the email address?

[MovGP0]

@blowdart yes, that's correct.

[HaoK]

@blowdart @ajcvickers

How about we make a breaking change and just add NormalizeName and NormalizeEmail (and getting rid of the old Normalize) in ILookupNormalizer instead of adding two new marker interfaces. Our default implementation can continue to just ToUpper both, but then its an easy drop in to tweak the normalization of either/both however people like.

[MovGP0]

@HaoK that would be a possible solution. I'm just unsure if it aheres to the SRP to do so. And to have four interfaces (INormalizerBase, IEmailNormalizer, IUserNameLookupNormalizer, AND INormalizer) seems like overkill.

[ajcvickers]

@HaoK Sounds okay to me.

[blowdart]

Works for me, SRP be damned. There's clean, and then there's pragmatic and usable :)