If a term is '0' clicking on its "Count" value displays all posts

[jesin]

To replicate:

• Create a post category named "0" (just the number without quotes).
• Assign a few posts to this category.
• Go to WP-Admin > Categories and the "Count" column in the "0" row will display the number of posts assigned to this category. Click on this number.

Now instead of displaying posts with the category "0", all posts are displayed irrespective of the category.

This issue isn't unique to post categories. It happens with custom taxonomies too.

[desrosj]

Thanks for opening this, @jesin!

This is most likely being caused by a loose comparison or two somewhere. The first part of the problem looks to be

I tracked part of the issue to this conditional (introduced in [15860]). But, in my initial testing, there is still another loose comparison somewhere.

[jesin]

I tracked down this issue to this array_filter function. Before being passed through this function the $query variable contains the following data:

Array
(
    [taxonomy] => category
    [terms] => Array
        (
            [0] => 0
        )

    [field] => name
    [operator] => IN
    [include_children] => 1
)

The array in the terms index is removed by array_filter().

How about replacing it with

$terms = array_filter( $query['terms'], function( $term ) { return ( 0 !== strlen( trim( $term ) ) ); } );

Also this issue occurs even when programmically retrieving posts using tax_query. The following code returns an empty array even if there are posts assigned to the "0" category.

get_posts( array( 'posts_per_page' => -1, 'fields' => 'ids', 'tax_query' => array( array( 'taxonomy' => 'category', 'field' => 'name', 'terms' => '0' ) ) ) )

[clescuyer]

A very similar issue happens with tags. To replicate:

• Create a post tag named "0" (just the number without quotes).
• Add this tag to a few posts
• Go to WP-Admin > Tags and the "Count" column in the "0" row will display the number of posts with this tag. Click on this number.

Now instead of displaying posts with the category "0", no posts are displayed.

For the categories, I used the array_filter() with the callback @jesin suggested. For the tags I suggest an enhanced test instead of ! empty( $q[ $t->query_var ] ).

Issue analyzed and solved during WordCamp Paris 2019 Contributor day.