".

/**
 * 1) Ignore bogus product_cat=0 some search forms submit
 *    and force search to products (optional).
 */
add_action('pre_get_posts', 'd10_fix_search_product_cat_zero', 5);
function d10_fix_search_product_cat_zero( $q ){
    if ( is_admin() ) return;
    if ( ! ($q instanceof WP_Query) ) return;
    if ( ! $q->is_main_query() ) return;
    if ( ! $q->is_search() ) return;

    // If the form sent product_cat=0, remove it
    $pc = $q->get('product_cat');
    if ( $pc === '0' || $pc === 0 ) {
        $q->set('product_cat', '' );

        // Also scrub tax_query clauses that target product_cat=0
        $tax_query = (array) $q->get('tax_query');
        if ( $tax_query ) {
            $new = array();
            foreach ( $tax_query as $clause ) {
                if ( is_array($clause)
                     && isset($clause['taxonomy']) && $clause['taxonomy'] === 'product_cat'
                     && isset($clause['terms'])
                     && ( $clause['terms'] === 0 || $clause['terms'] === '0'
                           $clause['terms'] === array(0)  $clause['terms'] === array('0') ) ) {
                    // skip this clause
                    continue;
                }
                $new[] = $clause;
            }
            $q->set('tax_query', $new);
        }
    }

    // Optional: keep search limited to products
    $q->set('post_type', array('product'));
}

/**
 * 2) Join tag tables so search can match product_tag name/slug
 */
add_filter('posts_join', 'd10_search_join_tags', 10, 2);
function d10_search_join_tags( $join, $q ){
    if ( is_admin()  ! $q->is_main_query()  ! $q->is_search() ) return $join;
    global $wpdb;

    if ( strpos($join, "{$wpdb->term_relationships}") === false ) {
        $join .= " LEFT JOIN {$wpdb->term_relationships} tr ON (tr.object_id = {$wpdb->posts}.ID)";
    }
    if ( strpos($join, "{$wpdb->term_taxonomy}") === false ) {
        $join .= " LEFT JOIN {$wpdb->term_taxonomy} tt ON (tt.term_taxonomy_id = tr.term_taxonomy_id AND tt.taxonomy='product_tag')";
    }
    if ( strpos($join, "{$wpdb->terms}") === false ) {
        $join .= " LEFT JOIN {$wpdb->terms} t ON (t.term_id = tt.term_id)";
    }
    return $join;
}

/**
 * 3) Extend WHERE to include tag name/slug LIKE the search term
 */
add_filter('posts_where', 'd10_search_where_tags', 10, 2);
function d10_search_where_tags( $where, $q ){
    if ( is_admin()  ! $q->is_main_query()  ! $q->is_search() ) return $where;
    global $wpdb;
    $term = $q->get('s');
    if ( ! $term ) return $where;

    $like = '%' . $wpdb->esc_like($term) . '%';
    $where .= $wpdb->prepare(
        " OR (tt.taxonomy='product_tag' AND (t.name LIKE %s OR t.slug LIKE %s))",
        $like, $like
    );
    return $where;
}

/**
 * 4) Avoid duplicates when multiple tags match
 */
add_filter('posts_distinct', 'd10_search_distinct', 10, 2);
function d10_search_distinct( $distinct, $q ){
    if ( is_admin()  ! $q->is_main_query()  ! $q->is_search() ) return $distinct;
    return 'DISTINCT';
}