Introduce generic filter on transient return value

[johnbillion]

The get_transient() and get_site_transient() functions have a filter on their return value, but the filter name contains the transient key: transient_{$transient}.

This means it's not possible to hook into the return value for every transient in order to do something like logging transient hits and misses.

[johnbillion]

Note that the patch on ticket #24685 is needed in conjunction with this to be of any real use.

[nacin]

Do we do anything similar for options, meta, or cache?

[johnbillion]

Nope, we don't do it for options, meta, or cache. I think it has a use case for transients though (and possibly the object cache, although that could impact performance). My use case is for logging hits and misses when fetching transients.

[nacin]

IRC discussion: ​http://irclogs.wordpress.org/chanlog.php?channel=wordpress-dev&day=2013-09-17&sort=asc#m689641

Maybe an 'expired_transient' action would be useful. But if you're using a cache backend, you'll get hit and miss statistics automatically.

[adamsilverstein]

updated patch for new use case

[welcher]

I have a use case where a generic filter would be extremely useful.

I have written a plugin to bypass transients on a per page basis ​https://github.com/ryanwelcher/suspend-transients. In order to bypass transients, we need to know their names.

Getting the name requires retrieving them from the database or capturing them using the setted_transient action and then storing them somewhere ( in my case an option )

Once we have the names of the transients, we then have to add a filter for each one - which can be a very large number of filters to add - and will eventually cause performance issues.

Having a generic filter would address both these issues.

[welcher]

Adds unit tests

[spbriggs]

Could this also be added to get_site_transient?

[netweb]

Moving reopened tickets without a milestone back to Awaiting Review for review

[adamsilverstein]

24686.2.diff​ adds a matching filter for get_site_transient

24686.3.diff​ is an alternate version which fires actions before the transients are returned.

Offering do_action as an alternative based on the IRC discussion: ​http://irclogs.wordpress.org/chanlog.php?channel=wordpress-dev&day=2013-09-17&sort=asc#m689641

[adamsilverstein]

24686.4.diff​ rename hooks, change "getted" to "got".

[adamsilverstein]

@nacin, @johnbillion what do you think of the approach in 24686.4.diff​ triggering an action?