Only show terms used by Post Type

I saw this post which was not resolved: https://www.ads-software.com/support/topic/hide-empty-terms-didnt-work-for-custom-taxonomy-in-multiple-custom-post-type

I don’t think it’s reasonable to suggest using taxonomies exclusively for a single post type…

My workaround solution is to include only terms assigned to published posts of a single type, via beautiful_filters_dropdown_categories filter.

In my case I used post type ‘product’ and taxonomy ‘mm’

function get_terms_id_by_post_type( $taxonomies, $post_types ) {
    global $wpdb;
    $query = $wpdb->get_col( "SELECT t.term_id from $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id INNER JOIN $wpdb->term_relationships AS r ON r.term_taxonomy_id = tt.term_taxonomy_id INNER JOIN $wpdb->posts AS p ON p.ID = r.object_id 
    	WHERE p.post_status = 'publish' 
    		AND p.post_type IN('" . join( "', '", $post_types ) . "') 
    		AND tt.taxonomy IN('" . join( "', '", $taxonomies ) . "') 
    	GROUP BY t.term_id");
    return $query;
}

function modify_categories_dropdown( $args, $taxonomy ) {
	$types = array('product');
	$tax = 'mm';
	if ( $taxonomy == $tax ) {
		$terms = get_terms_id_by_post_type( array($tax), $types );
		$term_list = ! empty($terms) ? implode(',', $terms) : false;
		if ( $term_list ) {
			$args['include'] = $term_list;
		}
	}
    return $args;
}
add_filter( 'beautiful_filters_dropdown_categories', 'modify_categories_dropdown', 10, 2 );