[wp-trac] [WordPress Trac] #64950: wp_using_ext_object_cache can return null, causing type failures, potential fatals

[WordPress Trac]

#64950: wp_using_ext_object_cache can return null, causing type failures, potential
fatals
--------------------------+--------------------------
 Reporter:  ronalfy       |       Owner:  westonruter
     Type:  defect (bug)  |      Status:  reviewing
 Priority:  normal        |   Milestone:  7.1
Component:  Cache API     |     Version:  3.7
 Severity:  normal        |  Resolution:
 Keywords:  has-patch     |     Focuses:
--------------------------+--------------------------

Comment (by liaison):

 Replying to [comment:4 westonruter]:
 > @liaison Inside `wp_using_ext_object_cache()`, wouldn't it be helpful if
 it emitted a `_doing_it_wrong()` if `$_wp_using_ext_object_cache` is
 `null`?
 >
 > I'm trying to reproduce the issue here. In the wordpress-develop
 environment with `LOCAL_PHP_MEMCACHED=true` added to `.env`, I'm seeing
 that `wp_using_ext_object_cache()` is returning `true` even when when an
 mu-plugin is added with:
 >
 > {{{#!php
 > <?php
 > var_dump( wp_using_ext_object_cache() );
 > }}}
 >
 >
 > However, I ''do'' see it output `NULL` if added to `db.php`. So it seems
 this is specifically an issue with `db.php`.
 >
 > Nevertheless, if I have `LOCAL_PHP_MEMCACHED=false` in my `.env`, then
 `wp_using_ext_object_cache()` is returning `NULL` even very late in the
 execution cycle.
 >
 > {{{#!php
 > <?php
 > add_action( 'template_redirect', function () {
 >       var_dump( wp_using_ext_object_cache() );
 > } );
 > }}}
 >
 > So it seems the function has always returned `null` if there is no
 `object-cache.php` drop-in? Apparently its return values are `null|true`?

 I've refined the PR with _doing_it_wrong() check specifically for the null
 state while maintaining type safety (returning false instead of null).
 Also to include a function_exists() check for _doing_it_wrong(). This
 ensures compatibility during the very early bootstrap stages (like db.php)
 where the function might not be defined yet. I've also ensured the return
 type is strictly boolean as discussed.

 {{{#!php
 <?php
 function wp_using_ext_object_cache( $using = null ) {
         global $_wp_using_ext_object_cache;

         // Save the current state to return later.
         $current_using = $_wp_using_ext_object_cache;

         if ( null !== $using ) {
                 $_wp_using_ext_object_cache = (bool) $using;
         }

         if ( null === $_wp_using_ext_object_cache ) {
                 if ( function_exists( '_doing_it_wrong' ) ) {
                         _doing_it_wrong(
                                 __FUNCTION__,
                                 __( 'This function should not be called
 before the object cache is initialized.' ),
                                 '7.1.0'
                         );
                 }

                 // If the global is uninitialized, the value would be
 null, which violates the type signature.
                 return false;
         }

         return (bool) $current_using;
 }
 }}}

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/64950#comment:5>
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