Here is an overview of the developer facing changes focused on user roles and capabilities for the 4.9 cycle. If you’re interested in more detail, checkout the full list of tickets.
Activating and deactivating plugins
It is now possible to manage capabilities for activating and deactivating plugins more granularly through the following new capabilities:
activate_plugin checks whether a user can activate a specific plugin A plugin is a piece of software containing a group of functions that can be added to a WordPress website. They can extend functionality or add new features to your WordPress websites. WordPress plugins are written in the PHP programming language and integrate seamlessly with WordPress. These can be free in the WordPress.org Plugin Directory https://wordpress.org/plugins/ or can be cost-based plugin from a third-party. When checking the capability, it gets passed the plugin file (such as
current_user_can( 'activate_plugin', 'my-plugin/my-plugin.php' )).
deactivate_plugin works similar to
activate_plugin, but checks whether a user can deactivate a specific plugin as the name indicates.
deactivate_plugins allows to check whether a user can generally deactivate plugins.
By default, all of the above capabilities map to the existing primitive capability
activate_plugins, so there is no change in behavior by default. However they make it possible to customize the behavior, for example to prevent specific users from activating or deactivating specific plugins. See #38652 for background discussion.
Installing and updating language files
The other group of new meta Meta is a term that refers to the inside workings of a group. For us, this is the team that works on internal WordPress sites like WordCamp Central and Make WordPress. capabilities deals with installing and updating language files / translations:
install_languages checks whether a user can install new language files.
update_languages checks whether a user can apply language file updates.
By default, the capabilities are granted to a user when they have at least one of the existing
install_themes capabilities. In addition, if
false, the capability checks will return
false as well. Again there is no change in behavior, but these capabilities allow customizing permissions more granularly, for example to not allow any updates other than language file updates. See #39677 for background discussion.
Hardening security against prohibited actions
When going through the
map_meta_cap() function, several capabilities end up mapping to a value of
do_not_allow, which is not an actual capability that should be used, but rather indicate that a user should under no circumstances be allowed to perform the respective action. However, it has historically been possible to manually grant users
do_not_allow as an actual capability, which is a bad practice and would cause unexpected behavior. As of 4.9, it is no longer possible to do that. See #41059 for background discussion.
Refactored user capability and role switching in multisite Used to describe a WordPress installation with a network of multiple blogs, grouped by sites. This installation type has shared users tables, and creates separate database tables for each blog (wp_posts becomes wp_0_posts). See also network, blog, site
In multisite, switching the available roles and the current user’s capabilities no longer happens in
restore_current_blog(), instead it has been moved to a new function
wp_switch_roles_and_user() which is hooked into the site switching process. This allows to improve performance by temporarily unhooking the function in cases where roles and capabilities do not need to be switched.
Furthermore the logic for both switching user capabilities in
WP_User and switching available roles in
WP_Roles has been refactored to work in a similar manner and provide more granular methods:
WP_User::_init_caps() methods have been deprecated in favor of
WP_Roles::_init() has been deprecated in favor of
WP_Roles now provide a
get_site_id() method to retrieve the ID for which the user’s capabilities/available roles respectively are currently initialized.
All these changes heavily benefit the process of switching sites, particularly by fixing a bug A bug is an error or unexpected result. Performance improvements, code optimization, and are considered enhancements, not defects. After feature freeze, only bugs are dealt with, with regressions (adverse changes from the previous version) being the highest priority. where available roles were not switched correctly prior. See #36961 and #38645 for background discussion.
Having a clean foundation now, several areas now deal with the available roles correctly when in a switched state. See #42013, #42014 and #42015 for the individual tickets.