Error when deleting media if default taxonomies have been removed

[imatoni]

Hello,

I recently had a problem with deleting media from the media library.

I received the following error message:

2151#0: *203114 FastCGI sent in stderr: "PHP message: UM_TEST_ERROR_LOG
PHP message: 63870
PHP message: "category"
PHP message: UM_TEST_ERROR_LOG
PHP message: 63870
PHP message: "post_tag"
PHP message: PHP Fatal error: Uncaught TypeError: array_map(): Argument #2 ($array) must be of type array, WP_Error given in /var/www/vhosts/fis-gmbh.de/stage.fis-gmbh.de/wp-includes/taxonomy.php:1964
Stack trace:
#0 /var/www/vhosts/fis-gmbh.de/stage.fis-gmbh.de/wp-includes/taxonomy.php(1964): array_map()
#1 /var/www/vhosts/fis-gmbh.de/stage.fis-gmbh.de/wp-includes/post.php(6304): wp_delete_object_term_relationships()
#2 /var/www/vhosts/fis-gmbh.de/stage.fis-gmbh.de/wp-includes/post.php(3416): wp_delete_attachment()
#3 /var/www/vhosts/fis-gmbh.de/stage.fis-gmbh.de/wp-admin/includes/ajax-actions.php(886): wp_delete_post()
#4 /var/www/vhosts/fis-gmbh.de/stage.fis-gmbh.de/wp-includes/class-wp-hook.php(324): wp_ajax_delete_post()
#5 /var/www/vhosts/fis-gmbh.de/stage.fis-gmbh.de/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()
#6 /var/www/vhosts/fis-gmbh.de/stage.fis-gmbh.de/wp-includes/plugin.php(517): WP_Hook->do_action()
#7 /var/www/vhosts/fis-gmbh.de/stage.fis-gmbh.de/wp-admin/admin-ajax.php(1" while reading response header from upstream

This happened because we had used the following code elsewhere:
add_action( 'init', 'deregister_tag' );
function deregister_tag() {
global $wp_taxonomies;
$tax = 'post_tag';
if ( taxonomy_exists( $tax ) ) {
unset( $wp_taxonomies[ $tax ] );
}
}

This code ensures that the standard WordPress taxonomy 'post_tag' is no longer present (this was not necessary for this project).

In wp-includes/post.php there is the following call:
wp_delete_object_term_relationships( $post_id, array( 'category', 'post_tag' ) );
This call causes an error to occur if the taxonomy 'post_tag' is not present.

I am of the opinion that this error should be caught in the WordPress core.

This issue is also being discussed here at WPML:
​https://wpml.org/forums/topic/fatal-error-when-deleting-a-media/

Thank you.

[imatoni]

oops, the first lines in the error message came from my error log. Of course, they do not come from the core.

This comes from my error_log():

UM_TEST_ERROR_LOG
PHP message: 63870
PHP message: "category"
PHP message: UM_TEST_ERROR_LOG
PHP message: 63870
PHP message: "post_tag"

https://core.trac.wordpress.org/ticket/60052#no0

that causes crit errors if default taxonomies catergory / post_tag have been removed or disabled.

The following line is a more generic check that would check category and post tag if they existed.

Deleted: wp_delete_object_term_relationships( $post_id, array( 'category', 'post_tag' ) );

This following line does the same thing but doesn't fail if empty, and covers any custom taxonomies.

Following line:

wp_delete_object_term_relationships( $post_id, get_object_taxonomies( $post->post_type ) );

[jeremyprentice]

​https://github.com/WordPress/wordpress-develop/pull/6230

has patch

[jeremyprentice]

​https://github.com/WordPress/wordpress-develop/pull/6230

Instead of removing the line, checks added.

Needs unit tests

[anthonythorne]

Testing Criteria & Summary of Unit Test

Testing Criteria:
Ensure that an attachment can be deleted even when the post_tag taxonomy has been unregistered.
Verify that wp_delete_attachment() correctly handles the absence of post_tag without errors.
Simulate real-world conditions by unregistering both category and post_tag taxonomies before deleting the attachment.
Confirm that the function returns a valid WP_Post object upon successful deletion.

Unit Test Summary:
This unit test creates a test attachment, unregisters the category and post_tag taxonomies, and then attempts to delete the attachment using wp_delete_attachment(). In previous versions, deleting an attachment after unregistering post_tag could cause a failure (#60052). The test ensures that after the core patch, the function correctly handles missing taxonomies and successfully deletes the attachment. The test also explicitly removes taxonomy entries from $wp_taxonomies to fully replicate the missing taxonomy scenario.

Let me know if you'd like any refinements!

[jeremyprentice]

​https://github.com/WordPress/wordpress-develop/pull/6230

@anthonythorne credit for completing the PHPUnit testing.

@jamespayne credit for removing the duplicate calls