Omit 404 pages from front-end search results

[joemaller]

Pages assigned the 404 template should not be appearing in front-end search results.

[joemaller]

Something like this:

function omit404s($query)
{
    if ($query->is_search && !is_admin()) {
        $args = [
            "posts_per_page" => -1,
            "post_type" => "page",
            "meta_query" => [
                [
                    "key" => "_wp_page_template",
                    "value" => "404.php",
                ],
            ],
        ];
        $templateQuery = new \WP_Query($args);
        $omitIDs = wp_list_pluck($templateQuery->posts, "ID");
        $query->set("post__not_in", $omitIDs);
    }
    return $query;
}
add_filter("pre_get_posts", "omit404s");

Does the name of a plugin-injected template match the file in the plugin or is that something we get to set? ref: #16