How to filter terms from a custom taxonomy by a usermeta value on all screens and templates

Question

I have a custom taxonomy "q_client" - each time a new term is added to this tax the ID of the user is stored in user_meta.

So each user has an array of id of the terms they have added - a quick hack to get around the lack of a taxonomy_meta table.

So - I'd like to use pre_get_posts to only include the terms that this user has added on ALL views - admin and front-end.

Here is what I've got so far:

Add the action:

add_action( 'pre_get_posts', array ( $this, 'tax_query' ), 2 );

The method

public function tax_query( $query ) 
{

        // get our existing user meta - or an empty array ##
        $q_client_terms = $this->get_q_client_terms();

        wp_die(var_dump($query));

        if ( $query->is_tax( 'q_client' ) ) {

            wp_die(var_dump($q_client_terms));

            $taxquery = array(
                array(
                    'taxonomy'  => 'q_client',
                    'field'     => 'id',
                    'terms'     => $q_client_terms,
                    'operator'  => 'IN'
                )
            );

            $query->set( 'tax_query', $taxquery );
            return $query;

        }

}

The main problem is I can't get is_tax or any other query variable to catch correctly - var_dump($query) gives a boolean false on is_tax() - it does not even know which post type this is on when editing the taxonomy via the admin.

Any help would be much appreciated - thanks!

EDIT

Thanks to @Milo - here is the code I now use:

   function get_terms_args( $args, $taxonomies ) {

        global $pagenow; // required if you want to only filter on certain pages ##

        if( 
            //is_admin()
            //&& 'edit-tags.php' == $pagenow
            //&& 
            'q_client' == $taxonomies[0] 
        ) {

            // get our existing user meta - or array ( -1 ) to exclude all terms ##
            $q_client_terms = $this->get_q_client_terms();

            // add array of terms to the include key ##
            $args['include'] = $q_client_terms; 

        }

        // kick back args Array ##
        return $args;

    }

One thing to note is that if each user has not added any terms and your return an empty array or an array( 0 ) - they will be shown all the terms - so use array( -1 ) to ensure they are all hidden

I've used this filter on all requests to this taxonomy as I want to filter everywhere - not just the admin

Answer 1

The issue with a taxonomy screen on the admin side is that it isn't a taxonomy archive. An archive is a collection of posts, a taxonomy admin screen is a collection of terms. The terms on those screens are loaded via get_terms, and the filter to modify those arguments is get_terms_args. Something like this should be able to catch those queries, where you can set the include argument:

function wpa_filter_term_args( $args, $taxonomies ) {
    global $pagenow;
    if( is_admin()
        && 'edit-tags.php' == $pagenow
        && 'q_client' == $taxonomies[0] ){
            // assuming $q_client_terms is an array
            $args['include'] = $q_client_terms; 
    }
    return $args;
}
add_filter( 'get_terms_args', 'wpa_filter_term_args', 10, 2 );