[wp-trac] [WordPress Trac] #23290: When using switch_to_blog() with a persistent object cache that lacks wp_cache_switch_to_blog() support, non-persistent groups are not maintained

[WordPress Trac]

#23290: When using switch_to_blog() with a persistent object cache that lacks
wp_cache_switch_to_blog() support, non-persistent groups are not maintained
-------------------------------------------------+-------------------------
 Reporter:  markjaquith                          |       Owner:
                                                 |  johnjamesjacoby
     Type:  defect (bug)                         |      Status:  closed
 Priority:  low                                  |   Milestone:  7.0
Component:  Cache API                            |     Version:  3.5
 Severity:  normal                               |  Resolution:  fixed
 Keywords:  has-patch needs-testing 2nd-opinion  |     Focuses:  multisite
-------------------------------------------------+-------------------------
Changes (by johnjamesjacoby):

 * status:  assigned => closed
 * resolution:   => fixed


Comment:

 In [changeset:"61760" 61760]:
 {{{
 #!CommitTicketReference repository="" revision="61760"
 Cache API: Introduce fallback for when the `wp_cache_switch_to_blog()`
 function is missing.

 This commit protects against an edge-case where a persistent object-cache
 drop-in plugin not including its own `wp_cache_switch_to_blog()` function
 would cause non-persistent cache groups to go missing when switching
 between sites, and includes the following changes:

 * A new `wp_cache_switch_to_blog_fallback()` function in `ms-blogs.php`
 which abstracts duplicated code from `switch_to_blog()` and
 `restore_current_blog()` for easier unit testing
 * A new `wpCacheSwitchToBlogFallback.php` file with approximately 25 new
 unit tests
 * Conditionally declares `wp_cache_switch_to_blog()` in `cache-compat.php`
 only if it does not already exist, either via core's `cache.php` or a
 drop-in plugin

 With this change, WordPress no longer needs to check if the
 `wp_cache_switch_to_blog()` function exists (because it always will) so
 those checks have been removed.

 Props ethitter, jeremyfelt, johnjamesjacoby, markjaquith, nacin, ozgursar,
 r1k0.

 Fixes #23290.
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/23290#comment:24>
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