Support for User taxonomies: Automatically add menu items and admin screens, add support for tax args to WP_User_Query

[helgatheviking]

Apparently it is possible to register a taxonomy for Users:

function create_user_tax() {
    register_taxonomy(
        'group',
        'user',
        array(
            'label' => __( 'Group' )
        )
    );
}
add_action('init', 'create_user_tax');

as described in [Justin Tadlock's tutorial](​http://justintadlock.com/archives/2011/10/20/custom-user-taxonomies-in-wordpress).

And wp_set_object_terms() and wp_get_object_terms() already work (though it *just* occurred to me there could be a slight issue if a user ID has the same ID as a post and they share a taxonomy), but as the tutorial describes you need to add your own Manage terms page *and* your own term count callback. I'd like to propose that those be added automatically just like any post type taxonomy.

I'd also like to propose WP_User_Query support tax_query args the same as posts. The query can already be modified via pre_get_users to support this, I think it'd just be cooler if it were in core.

function user_tax_query( $query ) { 
    global $wpdb;
    
    // fake a tax query
    if ( isset( $query->query_vars['tax_query'] ) && is_array( $query->query_vars['tax_query'] ) ) {
        
        $tax_args = $query->query_vars['tax_query'];

        if ( isset( $tax_args['taxonomy'] && isset( $tax_args['terms'] ) ) ) {
            $args = array(
        		array(
        			'taxonomy' => $tax_args['taxonomy'],
        			'field'    => 'slug', // eventually account for IDs
        			'terms'    => isset( $tax_args['terms'] ),
        		),
        	);
	        $sql = get_tax_sql( $args, $wpdb->prefix . 'users', 'ID' );
       
        
            if( isset( $sql['join'] ) ){
                $query->query_from .= $sql['join'];
            }
            
            
            if( isset( $sql['where'] ) ){
                $query->query_where .= $sql['where'];
            }
            
        }
    }

} 
add_action( 'pre_user_query', 'user_tax_query' );

With that filter in place a WP_User_Query can query the users in a specific taxonomy:

$args = array( 'tax_query' => array(
                    array(
                        'taxonomy' => 'group',
                        'field'    => 'slug',
                        'terms'    => 'blue-group',
                    ),
                )
            );


$users = new WP_User_Query( $args );

[boonebgorges]

Hi @helgatheviking ! Thanks for the ticket. The specific idea of supporting 'tax_query' in WP_User_Query is being discussed in #31383, in the more general context of better core support for user taxonomies. Please follow along there!