[wp-trac] [WordPress Trac] #21734: Completely remove global terms

[WordPress Trac]

#21734: Completely remove global terms
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 Reporter:  scribu                                |       Owner:  (none)
     Type:  enhancement                           |      Status:  reopened
 Priority:  normal                                |   Milestone:  6.1
Component:  Networks and Sites                    |     Version:
 Severity:  normal                                |  Resolution:
 Keywords:  has-patch 2nd-opinion needs-dev-note  |     Focuses:  multisite
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Changes (by desrosj):

 * keywords:  has-patch => has-patch 2nd-opinion needs-dev-note
 * milestone:  Future Release => 6.1


Comment:

 I think it's time to revisit this and follow through. A summary of some
 fact finding:

 - The UI was completely removed in [14854]. (WordPress 3.0)
 - The "on" switch was removed from Core in [14880]. A plugin was then
 required to trigger `install_global_terms()`. (WordPress 3.0)
 - The [https://wordpress.org/plugins/global-terms/ Global Terms plugin]
 that was created to push folks using the feature to does not work, and
 [https://wordpress.org/support/topic/wp-35-rc1-global-terms-10-not-work/
 appears to have been broken since WordPress 3.5].
 - After term splitting, there are lots of strange behaviors, problems, and
 broken-ness when changing terms that exist on multiple sites in my limited
 testing.
 - The concept of term meta now exists, but is not a thing in the context
 of global terms. There are likely lots of problems here as well.
 - Searches of the plugin directory confirm that
 [https://wpdirectory.net/search/01GA1N2136R48E66T71NVN0CVK no one] is
 [https://wpdirectory.net/search/01GA1HRPDEC5ZXDWJKHPN3BA1X actually]
 [https://wpdirectory.net/search/01GA1HQ4ZS72JAC3JP7V167NAN using] the
 [https://wpdirectory.net/search/01GA1HJPJD63VK95CXNND0DJEZ feature]. Most
 matches are plugins defensively using `global_terms_enabled()`, or false
 positives.

 I've created a PR to further deprecate and remove global terms. The PR:
 - Removes `global_terms_enabled()` calls within conditional logic making
 the assumption that global terms will never be enabled.
 - Moves all related functions to `ms-deprecated.php`.
 - Removes all default filter and action hooks calling these deprecated
 functions.
 - Introduces the concept of "old multisite global tables" mirroring "old
 tables" in WPDB and moves `sitecategories` into that list.

 One thing I was uncertain of was how to properly deprecate a pluggable
 function. I couldn't find any examples searching through the code base. If
 the function is moved to `ms-deprecated.php`, then I believe that it's
 technically no longer "pluggable" because of the file loading order (and
 the [https://github.com/WordPress/wordpress-
 develop/runs/7750333189?check_suite_focus=true#step:20:272 unit tests
 demonstrated this]). But leaving it in `pluggable.php` also felt wrong.

 If there's agreement this can happen, I'll close out global term related
 bug reports as `wontfix`. Also marking as `needs-dev-note`. One should be
 published as a courtesy to summarize this decision just in case there are
 sites still utilizing this.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/21734#comment:19>
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