Wrong cache created in WP_Term_Query class

[kubiq]

When you call the same get_terms( $args ) multiple times, then the second (or every other call) will return wrong results - they will contain also empty terms

You can easily test this on any taxonomy with some empty term

<?php
echo '1. call:';
echo '<pre>' . print_r( get_terms(array( 'taxonomy' => 'product_cat', 'parent' => 0 )), 1 ) . '</pre>';
echo '2. call:';
echo '<pre>' . print_r( get_terms(array( 'taxonomy' => 'product_cat', 'parent' => 0 )), 1 ) . '</pre>';

logically the output should be same in the 1.call and also in 2. call, but it's not

SOLUTION:

In get_terms function inside WP_Term_Query class at the end there is
wp_cache_add( $cache_key, $terms, 'terms' );
but $terms variable contains all terms even if you have hide_empty set to TRUE

*$term_objects is the correct variable that contains correct terms and it is also used in next lines

it can be fixed by getting terms ids from $term_objects variable eg.

<?php
$correct_terms = array_map(function( $term ){ return (object)array( 'term_id' => $term->term_id ); }, $term_objects);

and replace it in cache function

<?php
wp_cache_add( $cache_key, $correct_terms, 'terms' );

[audrasjb]

Thanks for finding this @kubiq!

The proposed solution looks good to me. Now we'll need a patch or a PR for this ticket :)

As per today's bug scrub, let's move this ticket to WP 6.0.1 as it appears it was introduced in 6.0.

[audrasjb]

Ah, it looks like it's probably a duplicate of #55837.

as per today's bug scrub, @kubiq is testing the issue on 6.1 alpha.

[audrasjb]

Removing close keyword as it appears that the issue is still valid on 6.1-alpha.

Related: #55837

[kubiq]

actually, it is solved in 6.1-alpha-53556
I tested it on 6.0.1-alpha-53446 previously
sorry for that - wrong settings in Beta tester plugin...

[SergeyBiryukov]

Great! Thanks for the follow-up.

#55837 will be backported to the 6.0 branch soon.