While customizing LearnDash I came across an issue in the topic.php file where the $lesson_post variable was returning null even when there was a parent lesson for the topic.
So, after digging around at the LearnDash source code a bit I came up with this simple solution to grab the lesson whenever I needed using the topic post which is accessible via $post.
|$parent_lesson_id = learndash_get_setting( $post, 'lesson' );|
|$parent_lesson = get_post( $parent_lesson_id );|
Not sure if others will find this helpful, but there are not a ton of extensive docs or articles on developing for LearnDash so wanted to share 🙂