WooCommerce extend product search by custom product data field

I’m currently trying to extend the WooCommerce product search so that the search uses my custom field I’ve created within the general product data section:

add_action( 'woocommerce_product_options_general_product_data', 'woocommerce_product_options_general_product_data_action', 9999, 0 );
function woocommerce_product_options_general_product_data_action(): void {
    global $post;

    echo '<div class="options_group">';

    woocommerce_wp_text_input( [
        'id'            => '_pdc_notch',
        'wrapper_class' => '',
        'label'         => 'Notch',
        'desc_tip'      => true,
        'type'          => 'text',
        'description'   => 'Enter notch PDC',
        'value'         => get_post_meta( $post->ID, '_pdc_notch', true )
    ] );

    echo '</div>';
}

add_action( 'woocommerce_process_product_meta', 'woocommerce_process_product_meta_action', 10, 1 );
function woocommerce_process_product_meta_action( int $product_id ): void {
    $pdc_notch = sanitize_text_field( wp_unslash( $_POST['_pdc_notch'] ?? null ) );

    update_post_meta( $product_id, '_pdc_notch', $pdc_notch );
}

With the above code, I can add and save my custom field. Now I’ve extended the search with the below hook:

add_action( 'woocommerce_product_query', 'woocommerce_product_query_action', 10, 2 );
function woocommerce_product_query_action( WP_Query $q, object $instance ) {
    if ( ! is_admin() && $q->is_main_query() && $q->is_search() ) {
        $meta_query = $q->get( 'meta_query' );

        $meta_query[] = [
            'key'     => '_pdc_notch',
            'value'   => $q->query['s'],
            'compare' => 'LIKE'
        ];

        $q->set( 'meta_query', $meta_query );
    }
}

When I set a text like “Iamabigtestword” to my field and put it in the search, I’m still getting nothing. What am I missing? I really can’t find the issue here. Normally, the hook should work (regarding an answer from StackOverflow: Include custom fields value in woocommerce search)

Note

You can copy/paste the code directly in the functions.php file of your child theme to test it, since it has no dependencies and should add the field to the Products > Product > General tab at the end.

Answer

I think I have found a way after some testing. First, I’ve debugged the WC function where the action gets applied, but changed my approach since I was making no progress. I’ve now extended the post search via the given WordPress filter:

add_filter( 'posts_search', 'filter_posts_search', 10, 2 );
/**
 * Extend product search to use the new custom field within search
 *
 * @param string $search
 * @param WP_Query $query
 *
 * @return string
 */
function filter_posts_search( string $search, WP_Query $query ): string {
    global $wpdb;

    if ( empty( $search ) || ! ( isset( $query->query_vars['s'], $query->query_vars['post_type'] ) && ! empty( $query->query_vars['s'] ) && $query->query_vars['post_type'] === 'product' ) || is_admin() || ! is_search() || ! is_main_query() ) {
        return $search;
    }

    $product_ids = [];

    $products = wc_get_products( [
        'post_type'    => 'product',
        'limit'        => - 1,
        'meta_key'     => '_pdc_notch',
        'meta_value'   => esc_attr( $query->query_vars['s'] ),
        'meta_compare' => 'LIKE' // or '='
    ] );

    /**
     * @var WC_Product $product
     */
    foreach ( $products as $product ) {
        $product_ids[] = $product->get_id();
    }

    $product_ids = array_unique( $product_ids );

    if ( count( $product_ids ) > 0 ) {
        $search = str_replace( 'AND (((', "AND ((({$wpdb->posts}.ID IN (" . implode( ',', $product_ids ) . ")) OR (", $search );
    }

    return $search;
}

I hope it helps someone! If someone finds a better approach, I can test it for you.