There is another thread on here that discusses a workaround. Well… the familiar php workaround when a function does not provide a “get to variable” output actually… use ob_start: http://php.net/manual/en/function.ob-start.php to just capture the output and manipulate it before sending it on its way. Leads on stackoverflow: https://stackoverflow.com/search?q=%2Bwordpress+sidebar+%2Bob-start+
Edit 2: By suggest of @Mark Kaplun, the general solution should be this. We will do filtering after the page is generated, so we won’t care about which plugin we’re using. We need a hack here to get whole page: ob_start(); add_action(‘shutdown’, function() { $final=””; // We’ll need to get the number of ob levels … Read more
Thought this was a great question so I went digging. In default-filters.php on line 208 there’s add_action(‘wp_head’, ‘noindex’, 1); as of WordPress 4.1. The noindex() function in turn checks to see if you have set blog_public option to 0. If you have, it calls wp_no_robots() which is simply: function wp_no_robots() { echo “<meta name=”robots” content=”noindex,follow” … Read more