Add a `pre_set_object_terms` action

[davidbaumwald]

Working with some custom terms & taxonomies, and it looks like there's no way to hook in to wp_set_object_terms _before_ the terms are updated.

In the end, the $old_tt_ids is passed to the set_object_terms action(added in r12261). But, these are the term_taxonomy_ids and a a bit harder to work with than the plain terms. Also, these are provided _after_ the terms are updated. So, there's no way to short-circuit the updating.

However, I think it would be useful to have a pre_ action that can work on the current terms before commiting the changes.

[sagarsavani7979]

This commit adds a new action hook, 'pre_set_object_terms', to the wp_set_object_terms function. This hook fires before an object's terms are set, allowing developers to perform operations or modifications on the terms array before the changes are committed.

This PR introduces a new pre_set_object_terms action that triggers before terms are assigned to an object in wp_set_object_terms. Currently, it is only possible to access term taxonomy IDs ($old_tt_ids) after terms have already been updated, which limits the ability to make adjustments prior to committing changes.

Trac ticket: https://core.trac.wordpress.org/ticket/60532

[geekofshire]

@sagarsavani7979 @davidbaumwald I have raised a PR, please do give it a look

[apermo]

@geekofshire @sagarsavani7979 Imho the position of the filter is broken as it is in the patch and PR. The position is too low, $object_id is already used before to fill $old_tt_ids. So under normal conditions $old_tt_ids will have the wrong content if $append is false

Also see: ​https://github.com/WordPress/wordpress-develop/pull/7660#discussion_r1820132363

[geekofshire]

Replying to apermo:

@geekofshire @sagarsavani7979 Imho the position of the filter is broken as it is in the patch and PR. The position is too low, $object_id is already used before to fill $old_tt_ids. So under normal conditions $old_tt_ids will have the wrong content if $append is false

Also see: ​https://github.com/WordPress/wordpress-develop/pull/7660#discussion_r1820132363

Thank you for the feedback! I’ve made adjustments based on your comments.