我正在尝试改变WooCommerce商店的搜索功能，以便当用户进行匹配product_tag slug返回未指定产品标签的产品。

这背后的逻辑是向搜索“面筋”的用户显示所有不含面筋的产品。

除了操作符参数外，我的代码几乎正常工作。

我正在抛出此查询：

http://example.com/?s=gluten

This function returns all the products tagged as the search query:

function menta_pre_get_posts( $query ) {
if ( !is_admin() && $query->is_search() && $query->is_main_query() ) {
    $term = get_term_by(\'slug\', get_query_var(\'s\'), \'product_tag\');
    if ( $term && !is_wp_error( $term ) ) {
        $tax_query = array(
                \'taxonomy\'  => \'product_tag\',
                \'field\'     => \'slug\',
                \'terms\'     => $term->slug,
                \'operator\'  => \'IN\'
        );
        $query->tax_query->queries[] = $tax_query;
        $query->query_vars[\'tax_query\'] = $query->tax_query->queries;
     }
}}
add_action( \'pre_get_posts\', \'menta_pre_get_posts\', 1 );

But if I change the operator to NOT IN, I get no results:

function menta_pre_get_posts( $query ) {
if ( !is_admin() && $query->is_search() && $query->is_main_query() ) {
    $term = get_term_by(\'slug\', get_query_var(\'s\'), \'product_tag\');
    if ( $term && !is_wp_error( $term ) ) {
        $tax_query = array(
                \'taxonomy\'  => \'product_tag\',
                \'field\'     => \'slug\',
                \'terms\'     => $term->slug,
                \'operator\'  => \'NOT IN\'
        );
        $query->tax_query->queries[] = $tax_query;
        $query->query_vars[\'tax_query\'] = $query->tax_query->queries;
     }
}}
add_action( \'pre_get_posts\', \'menta_pre_get_posts\', 1 );