Only return taxonomies that are linked to a category & product

Question

What's the best way, to return taxonomies, but only taxonomies that are linked to a product, within the category, I have a heirachial taxonomy, I want to get all the top level options, once an option is picked, I want to get all the children, but only the children that are linked to a product.

Is this possible?

Currently I'm just getting the immediate children of the first term picked, I don't know how to filter out the ones that have no matches.

This is the second request:

$terms = get_terms( 'tyre', array(
    'orderby'       => 'name',
    'child_of'      => $term_id,
    'hide_empty'    => $hide_empty
));

Is there a way to extend this to something like this:

$terms = get_terms( 'tyre', array(
    'orderby'       => 'name',
    'category'      => 'tyres',
    'only_linked_to_products' => true,
    'child_of'      => $term_id,
    'hide_empty'    => $hide_empty
));

Obviously I've just invented these two properties, but it would help illustrate what I'm trying to do

Answer 1

This will find all terms in custom taxonomy underkategorier and then will show terms with post from chosen category.

$taxonomies = get_taxonomies(array('name'=>'underkategorier'),'object'); 

foreach($taxonomies as $taxonomy) {
    $terms = get_terms( $taxonomy->name, 'orderby=count&hide_empty=0' );
    foreach($terms as $term) {
        $wpq = array ('taxonomy'=>'underkategorier','term'=>$term->slug, "cat"=>10);
        $myquery = new WP_Query ($wpq);
        $article_count = $myquery->post_count; 
        echo $term->name.' '.$article_count; //with empty ones
        if ($article_count){
            echo "<ul>";
            echo "<li>".$term->name.' '.$article_count."</li>";
            echo "</ul>";
        }
    }
}