Plugin interferes with other plugins modifying robots.txt

Hello!

If you want to ensure adding anything to a filter, then you must use a higher priority. I think this slipped Jeff’s mind because TSF does not interfere with that.

This snippet will do — it basically makes the default 10-priority an 11. The init-action-wrapper is there to mitigate plugin-race-conditions, and the function-exists wrapper is there to prevent a PHP error when the Blackhole plugin is deactivated.

add_action( 'init', function() {
	if ( function_exists( 'blackhole_robots_wordpress' ) )
		add_filter( 'robots_txt', 'blackhole_robots_wordpress', 11, 2 );
} );

I explained the reasoning behind overwriting the robots.txt output here… mind it’s difficult to read: https://github.com/sybrew/the-seo-framework/issues/339#issuecomment-546684189.