register_theme_directory() usage can break the current theme
|Reported by:||johnjamesjacoby||Owned by:|
Description (last modified by johnjamesjacoby)
It's possible for the active theme and it's roots to become out of sync when performing a specific set of actions, resulting in the site white-screening because of the active theme directory being incorrect.
Hard to explain, so I've included more information below.
Steps to reproduce:
- Activate BuddyPress.
- Activate bp-default theme.
- Deactivate BuddyPress.
- Visit Appearance > Themes. (Theme shows as 'Twenty Twelve')
- Visit site: Twenty Twelve appears
- Check DB: stylesheet and template are changed to 'twentytwelve'.
- Check DB: stylesheet_root and template_root still point to '/plugins/buddypress/bp-themes/'.
- Reactivate BuddyPress.
- Visit Appearance > Themes. (Theme shows as 'twentytwelve')
- twentytwelve reports back as broken.
- Visit site: white-screen of doom
- wp-admin/themes.php:line 107 calls validate_current_theme()
- wp-includes/theme.php:719 calls switch_theme()
- wp-includes/theme.php 682 counts $wp_theme_directories, and skips the roots.
- This results in the _root options pointing to '/plugins/buddypress/bp-themes', and the current stylesheet and template being set as 'twentytwelve'.
- If you re-activate BuddyPress, $wp_theme_directories will now be greater than 1, and the _root options will not get updated.
- Remove count( $wp_theme_directories ) check from switch_theme(). This forces the theme root to be accurate every time the theme switches, regardless of how many directories are ever registered. In my opinion, this is the most sensible option. (Patch attached)
- Improve search_theme_directories() to update 'stylesheet_root' and 'template_root' when 'theme_roots' transient doesn't match up. This works because we're already looping through the $cached_roots to make sure each theme is valid. The problem here is we're depending on the expiration of the transient, and doing additional logic each time that happens. (No patch attached)
The crux of the issue: counting $wp_theme_directories isn't a reliable way to guarantee the current theme and its _root's match. This bug doesn't occur if more than 1 additional theme directory is registered, because switch_theme() will always update the theme root in that circumstance.
By forcing switch_theme() to always save the roots, we're able to bypass the issue completely.
Conversely, the only reason to store the _root's is when register_theme_directory() is used more than once. If it's only used by core to register '/themes', it's never a problem. If it's always used by several plugins, it's never a problem. It's only a problem when switching between it being used more than once, and then only by core.
This results in two additional options (even when there are never multiple theme roots) which sucks, but it always fixes the bug.
If we fix it in search_theme_directories(), we're able to update the _root's when they need it, but we're performing that extra logic on each iteration when the transients expire. Also, because search_theme_directories() has some funky sub-directory checks, it's a messy bit to try and hack in there.