Trying to get both custom post type and posts to show up in tag and category pages - wordpress

Question

I've built a custom post type, that is set to use the out-of-the-box tags and categories that posts use. However, if I click on a tag or category link, the archive only shows posts with that tag, not my custom post type. I've tried a few ways to fix it but they don't seem to be working. My code is:
// Add Resource Post Type
add_action('init', 'hallam_init');
function hallam_init() {
// set up the labels
$labels = array(
'name' => _x('Resources', 'post type general name'),
'singular_name' => _x('Resource', 'post type singular name'),
'add_new' => _x('Add New', 'resource'),
'add_new_item' => __( 'Add New Resource' ),
'edit_item' => __( 'Edit Resource' ),
'new_item' => __( 'New Resource' ),
'view_item' => __( 'View Resource' ),
'search_items' => __( 'Search Resources' ),
'not_found' => __( 'No resources found' ),
'not_found_in_trash' => __( 'No respources found in Trash' ),
'parent_item_colon' => ''
);
// set up the args
$args = array (
'labels' => $labels,
'public' => true,
'publicly_queryable' => true,
'show_ui' => true,
'query_var' => true,
'rewrite' => array (
'slug' => 'resources'
),
'capability_type' => 'post',
'hierarchical' => false,
'menu_position' => 5,
'supports' => array(
'title',
'editor',
'author',
'thumbnail',
'excerpt',
'comments'
),
'taxonomies' => array(
'collection',
'category',
'post_tag'
),
'has_archive' => true
);
register_post_type('ht_resource', $args);
}
// Add Taxonomy
register_taxonomy('collection', 'ht_resource', array(
'hierarchical' => true,
'label' => 'Collections',
'query_var' => true,
'rewrite' => true
));
// Fix the archives
add_filter( 'pre_get_posts', 'add_to_query' );
function add_to_query( $query ) {
// if ( is_home() ) {
if( $query->query_vars['suppress_filters'] ) // TODO check if necessary
return $query;
$supported = $query->get( 'post_type' );
if ( !$supported || $supported == 'post' )
$supported = array( 'post', 'ht_resource' );
elseif ( is_array( $supported ) )
array_push( $supported, 'ht_resource' );
$query->set( 'post_type', $supported );
return $query;
//}
}
Am I missing something obvious?

Answer 1

Can you plz try this by adding on your theme's functions.php? Hope it will work
function query_post_type($query) {
if(is_tag()) {
$query->set('post_type',$post_types=get_post_types('','names'));
return $query;
}
}
add_filter('pre_get_posts', 'query_post_type');
thnx