advanced-cache.php is @included

[solarissmoke]

I've been working using some caching plugins recently and am finding that when errors happen, tracking down the problem can be very tricky until you realise that advanced-cache.php is @included - and then you have to manually edit the core files to remove the error suppression.

The @include was introduced in #4293, to replace a require().

Any objections to removing the @ ?

[nacin]

The issue is that then we'd probably want to introduce a file_exists. I assume the idea from #4293 was that silencing it is quicker than the file_exists check.

[Denis-de-Bernardy]

Rather than a file exists check, I'd suggest directing users to the misconfiguration problem. something like:

if ( false === include(cache file) ) {
  echo your site has a cache configuration problem. delete the WP_CACHE define in your wp-config.php file.
}

alternatively, we could temporarily strip E_WARNING from error reporting.

[Denis-de-Bernardy]

extra note: when in the admin area, and on the login screen, we shouldn't even be including that file. any unsilenced error in it prevents users from logging in because it forces php headers to be sent.

[sivel]

Remove the suppression and check for existence of file

[sivel]

I think that trade off for a file_exists outweighs the potential problems of suppressing all errors that come from this file inclusion.

Patch removes suppression and adds file_exists.

[nacin]

I don't like the idea of adding a file_exists check here. We do it in db.php and object-cache.php, but advanced-cache.php is included before both of them and may very well serve a static file and die, not loading any more of WP. It needs to be fast.

I'm sitting next to jjj and sivel, and we came up with this: Checking WP_DEBUG, and if true, don't suppress, otherwise, we do suppress errors. And no file_exists check. Thoughts?

[nacin]

(In [14345]) Don't silence inclusion of advanced-cache.php for WP_DEBUG. fixes #13185.