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