On my Woocommerce category pages, I want to grab the existing query results and use it to populate the schema data for OfferCatalog.

This is the closest function I can find to what I need:

/**
 * Add structured data to the WooCommerce shop page.
 *
 * @param array $markup The structured data markup.
 * @param WP_Query $query The current WP_Query object.
 * @return array The modified structured data markup.
 */
function add_structured_data_to_shop_page( $markup, $query ) {
    if ( is_shop() || is_product_category() || is_product_tag() ) {
        $markup['@type'] = 'CollectionPage';
        $markup['mainEntity']['@type'] = 'OfferCatalog';
        $markup['mainEntity']['itemListElement'] = array();

        $products = $query->get_posts();
        foreach ( $products as $product ) {
            $markup['mainEntity']['itemListElement'][] = array(
                '@type' => 'Product',
                'name' => get_the_title( $product->ID ),
                'url' => get_permalink( $product->ID ),
                'image' => get_the_post_thumbnail_url( $product->ID, 'full' ),
                'description' => get_the_excerpt( $product->ID ),
                'offers' => array(
                    '@type' => 'Offer',
                    'price' => get_post_meta( $product->ID, '_price', true ),
                    'priceCurrency' => get_woocommerce_currency(),
                    'availability' => 'https://schema.org/InStock', // Adjust as needed
                ),
            );
        }
    }

    return $markup;
}
add_filter( 'woocommerce_structured_data', 'add_structured_data_to_shop_page', 10, 2 );

But nothing is output. I suspect the woocommerce_structured_data has been disabled or removed from the category pages. I’ve tried different hooks, but still see nothing output.

How can I make this work (without repeating the database query)?