Disable core search query handling

disable_core_search.php

<?php

function disable_core_search_query_handling($query, $error = true) {
    if (is_search() && !is_admin()) {
        $query->is_search       = false;
        $query->query_vars['s'] = false;
        $query->query['s']      = false;

        // to error

        if ($error === true) {
            $query->is_404 = true;
        }
    }
}
add_action('parse_query', __NAMESPACE__ . '\disable_core_search_query_handling');