Plugin caching prevents detection of newly installed plugins

[Murmatron 2]

Use of wp_cache_get/wp_cache_set in get_plugins in /wp-admin/includes/plugin.php prevents a newly installed plugin from being detected until object cache is purged.

By the same mechanism, a plugin directory that has been manually zapped from the filesystem is shown as a recently deactivated plugin.

There's no obvious criterion for invalidating the cached object since it's created from a filesystem scan and actively prevents another one occurring.

Perhaps something like a "Scan disk for new/deleted plugins" button on the admin page that deletes the plugins cache would be a solution worth considering.

[DD32]

It sounds like the Object Cache has not been updated to respect the non-persistent groups introduced with #6740

A workaround i can think of is to manually purge the object cache groups upon each pageload if the group is registered as non-persistent.

As a side note: There are also some Object caches which appear to ignore the cache_flush()'s and will remember the cached data after its supposed to have been invalidated; I believe thats caused some issues elsewhere, But this is not specifically related to this ticket issue.

[ryan]

The cache backend needs to use the API from #6740. Some caches have already been changed, so you might need to update.