category_name not working (not showing up in sql query debug)

Question

My plugin has a shortcode and it retrieves animals. There are filters/arguments and they all work well except the category argument or parameter.

The category name(s) is/are well passed to my shortcode function but the WP_Query->request does not show any sign of category_name! I tried with cat and the ID, same, nothing shows up. Instead, it return an empty set of results.

    $filters    = array();
    $cat        = "";

    if( !empty($args['cat']) ) {
        $cat = trim($args['cat']);
    }

    $query = new WP_Query( array( 
        'post_type'         => 'animal',
        'category_name'     => 'rottweiler', /* ignored/breaks the sql query */
        'post_status'       => 'publish',
        'orderby'           => 'title',
        'order'             => 'asc',
        'numberposts'       => -1,
        'posts_per_page'    => -1,
        'meta_query'        => $filters
    ) );

    $animals = $query->get_posts();

    if( $animals ) {

        $columns = empty($args["columns"]) ? 2 : $args["columns"];

        $output .= '<div class="breedr"><ul class="columns '.number_to_words($columns).'">';

        foreach ( $animals as $animal ) {
            $output .= $this->breedr_template( plugin_dir_path( dirname( __FILE__ ) ) . 'public/partials/list-single-animal.php', $animal );
        }

        $output .= '</ul></div>';

    }
    else {
        $output .= "<span>No animal found.</span>";
    }

    return $output;

And this is what the debug sql returns - AND ( 0 = 1 ) is clearly posing problem here:

CAT: rottweiler
SELECT wp_2_posts.* FROM wp_2_posts WHERE 1=1 AND ( 0 = 1 ) AND wp_2_posts.post_type = 'animal' AND ((wp_2_posts.post_status = 'publish')) GROUP BY wp_2_posts.ID ORDER BY wp_2_posts.post_title ASC 

No animal found.

I am confused at what causes this problem. The category slug exists, every other parameter in this query works when I simply remove the category parameter.

Answer 1

If you're using custom taxonomy for your CPT, then you can't use params of WP_Query that are related with built-in categories - WP won't be able to guess what taxonomy should be queried.

So, let's say you have a custom taxonomy called animal_type, then your query should look something like this:

$query = new WP_Query( array( 
    'post_type'         => 'animal',
    'post_status'       => 'publish',
    'orderby'           => 'title',
    'order'             => 'asc',
    'posts_per_page'    => -1,
    'tax_query'         => array(
        array( 'taxonomy' => 'animal_type', 'field' => 'slug', 'terms' => 'rottweiler' )
    ),
    'meta_query'        => $filters
) );

Notice, that I've also deleted this part:

'numberposts'       => -1,

There is no such parameter for WP_Query. There was parameter called showposts, but it's deprecated.