Duplication and incompatibilities in register_new_user() and wp_insert_user()

[coffee2code]

As a result of [12778], the commit of a patch that was part of #11644 (the MU-merge ticket), wp_insert_user() was modified to introduce user verification checks. The addition of these checks also introduced a number of duplications and incompatibilities between it and register_new_user(). (Bear in mind that register_new_user() calls wp_create_user() which calls wp_insert_user().)

These issues include:

• Duplication (both run-time execution and code): both functions perform username_exists() and email_exists() checks. Ideally, we should only perform each check once, and from a single piece of code.
• Whereas both functions perform username_exists() and email_exists() checks, register_new_user() performs more checks (empty_username, invalid_username, empty_email, invalid_email). If the former 2 are being checked, all 6 criteria should be checked.
• wp_insert_user() can now return a WP_Error object, but register_new_user() can't handle it (I reported this in #14290)
• register_new_user() generates a new generic error if wp_create_user() (via wp_insert_user()) returns an error (assuming proper patch #14290), rather than passing along the more specific error it was told about

If an error is returned by wp_create_user(), register_new_user() throws a generic 'registerfail' error ('<strong>ERROR</strong>: Couldn&#8217;t register you... please contact the <a href="mailto:%s">webmaster</a> !'). However, most likely it received a more informative WP_Error object.

• register_new_user() allows errors to be suppressed via filters, but wp_insert_user() does not

register_new_user() has the filter 'registration_errors' which allows plugins to suppress any encountered errors. Having done so, register_new_users()'s subsequent call to wp_create_user() can generate an error (of the type already suppressed) which is then un-suppressable. This renders the 'registration_errors' filter useless for the username_exists and email_exists errors (and possibly other in the future).

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These different issues may warrant separate tickets, but cumulatively I think they point to the need to refactor register_new_user() and wp_insert_user() to be more efficient and compatible.

This is a rare instance where I don't include an immediate patch for a ticket, but I wanted to get it out there and see if we can try and get these fixed for 3.1.

[hakre]

Your considerations look very useful to me. Maybe starting with removing code duplication and putting the shared code into functions?

[wonderboymusic]

Combined code from both functions - passes unit tests / needs more testing. Patch attached.

[wonderboymusic]

Refreshed against trunk, I think this is still a good move - the code between the two funcs should be in sync

[nacin]

#14290 means this will need a refresh and possible reconsideration.