[wp-trac] [WordPress Trac] #59677: Incorrect theme returned when switching to blog in multisite subsite

[WordPress Trac]

#59677: Incorrect theme returned when switching to blog in multisite subsite
--------------------------------+-----------------------------
 Reporter:  codex-m             |      Owner:  (none)
     Type:  defect (bug)        |     Status:  new
 Priority:  normal              |  Milestone:  Awaiting Review
Component:  Networks and Sites  |    Version:  trunk
 Severity:  major               |   Keywords:
  Focuses:  multisite           |
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 I think I have found issue with the coming WordPress 6.4. I tested with
 latest WordPress 6.4 RC1.

 **Environment**

 PHP Version: 8.0
 Operating system: Ubuntu 20.04

 **Test code to reproduce the issue (e.g. save this as reproduce.php):**

 {{{#!php
 <?php
 ini_set('display_errors', 1);
 ini_set('display_startup_errors', 1);
 ini_set('error_reporting', E_ALL);

 require_once('wp-load.php');

 switch_to_blog(2);
 $template_path = get_template_directory();
 $stylesheet_path = get_stylesheet_directory();
 restore_current_blog();

 echo "PARENT THEME: {$template_path}";
 echo "<br />";
 echo "CHILD THEME: {$stylesheet_path}";
 }}}

 **How to reproduce the issue:**

 1.) Setup a fresh WordPress multisite.
 2.) Create a new subsite (BLOG ID: 2)
 3.) Activate a non-default theme (with parent and child theme) subsite
 BLOG ID: 2. For example, in this testing I use Astra parent and child
 theme).

 4.) Run the test script on the main site by calling it as:

 `https://yourmultisite.tld/reproduce.php`

 **Test result**:

 1.) WordPress 6.3.2 OUTPUT:

 PARENT THEME: `/home/emerson/sourcecode/subdomaintest/wp-
 content/themes/astra`
 CHILD THEME: `/home/emerson/sourcecode/subdomaintest/wp-content/themes
 /astra-child`

 2.) Latest WordPress 6.4 RC1 OUTPUT:

 PARENT THEME: `/home/emerson/sourcecode/subdomaintest/wp-
 content/themes/twentytwentythree`
 CHILD THEME: `/home/emerson/sourcecode/subdomaintest/wp-
 content/themes/twentytwentythree`

 **Test summary**:

 I expected to see the actual theme used in the subsite (blog ID: 2)
 instead I got the currently activated main site theme (incorrect).

 **Solution**

 I think the issue is that in WordPress 6.4, the result of these functions
 (`get_template_directory()` &
 `get_stylesheet_directory()`) are now stored into global variables for
 performance reasons. However the issue is that in multisite - these can be
 set first before the blog is switched thus preventing to return the
 correct value once the blog is switched.

 I think we can fix this by checking if the call is made in multisite and
 if the blog is already switched. Once switched, we unset these global
 variables so it will return the correct values.

 This is only my suggestion to fix this issue. Please attached patch.
 Thanks!

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Ticket URL: <https://core.trac.wordpress.org/ticket/59677>
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