id,summary,reporter,owner,description,type,status,priority,milestone,component,version,severity,resolution,keywords,cc
21730,More modular and reusable email validation functions,boonebgorges,,"Email validation, especially as it's handled in Multisite (most of which is verbatim from MU), is pretty messy. We have some functions like `is_email_address_unsafe()` for checking banned domains, but we don't have a parallel function for checking against limited_email_domains. There are no filters outside of `wpmu_validate_user_signup`, which means that if you want to use email validation outside of the normal MS registration workflow and want to tweak the way that it works (see eg #15706, #20459), you pretty much have to roll your own. And there's no single function that a plugin like BuddyPress can use to do all relevant email checks in one fell swoop.

The attached patch suggests the following changes:
- Put the limited_email_domains check into a function, `is_email_address_allowed()`.
- Put filters on the output of this new function as well as `is_email_address_unsafe()`.
- Introduce function wp_validate_email_address(), which wraps the following four checks: is_email(), email_exists(), is_email_address_allowed(), is_email_address_unsafe().
- Rearranges `wpmu_validate_user_signup()` a bit so that all email checks (as opposed to username checks) happen together.

I'm not married to anything in this particular implementation (the way that wp_validate_email_address() sends back error messages is not particularly beautiful, but I didn't want to introduce a ton of overhead), but I would really like to see some sort of treatment along these lines, to make things more modular and reusable.

If something like this gets approved by the devs, I would like to further suggest the following:
- Give a similar treatment to username validation
- Move the generic validation functions out of ms-functions.php (with function_exists() checks on the MS-specific stuff)

I'm happy to work more on this kind of patch, but didn't want to go too far in case it's a non-starter for some reason.",enhancement,new,normal,Awaiting Review,Users,,normal,,has-patch dev-feedback,