User creation fails for users with long names.

[cfinke]

Summary: When creating a user with a long first or last name, the query that inserts the user into the DB is assumed to have succeeded, but that fact is never verified.

Sign in as an admin and create a new user, giving it the first name ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQ (or any 251-byte string). After submitting the form, you'll see a handful of error messages (line numbers are from trunk just now, but I can reproduce the bug as far back as 4.2.1):

Notice: Trying to get property of non-object in wp-includes/pluggable.php on line 1716
Notice: Trying to get property of non-object in wp-includes/pluggable.php on line 1717
Notice: Trying to get property of non-object in wp-includes/pluggable.php on line 1730
Notice: Trying to get property of non-object in wp-includes/pluggable.php on line 1738
Notice: Trying to get property of non-object in wp-includes/pluggable.php on line 1740
Notice: Trying to get property of non-object in wp-includes/pluggable.php on line 1742
Notice: Trying to get property of non-object in wp-includes/pluggable.php on line 1746

Warning: Cannot modify header information - headers already sent by (output started at wp-includes/pluggable.php:1716) in wp-includes/pluggable.php on line 1171

What happens is that the $wpdb->insert( $wpdb->users, $data + compact( 'user_login' ) ); call in wp_insert_user() fails, but there's no check to ensure that it succeeded, so the code proceeds to try and create a new WP_User with ID 0. This results in unexpected behavior, like sending a "New User Registration" email to the admin with blank "Username" and "Email" values.

The failure is due to $wpdb->process_fields() calling $wpdb->strip_invalid_text(), which truncates the display_name field (because the display_name field only allows 250 bytes), and because it then doesn't match the value passed into $wpdb->process_fields(), it returns false. So this isn't so much a bug about a text string that's too long, it's really a bug about not checking the return value of $wpdb->insert().

I think the resolution of #10377 is probably the same kind of approach that could be taken here, since the problems seem similar.

[ocean90]

Related: #33793

[Presskopp]

see also

https://core.trac.wordpress.org/ticket/37555#comment:3