_fill_user does not handle multi-value usermeta keys properly

[bkrausz]

The following code, line 535ish of wp-includes/user.php

$metavalues = $wpdb->get_results($wpdb->prepare("SELECT meta_key, meta_value FROM $wpdb->usermeta WHERE user_id = %d", $user->ID));
$wpdb->show_errors($show);

if ( $metavalues ) {
    foreach ( (array) $metavalues as $meta ) {
        $value = maybe_unserialize($meta->meta_value);
        $user->{$meta->meta_key} = $value;
    }
}

This does not work for meta keys that have multiple values. Right now get_usermeta doesn't act according to spec because this fills the cache it pulls from.

[ryan]

Tracking this with #7540