Why save_post_$(custom_post_type) is fired even if I am not already saving a post?
When you choose “Your CPT > Add New”, WP calls get_default_post_to_edit(), which actually creates an “empty” post (with ‘post_status’ => ‘auto-draft’) and then calls wp_insert_post(). This is what is causing your save_datasheet_meta() function to be called before you think it should. Hence, generally you should add some additional sanity checks to the beginning of any … Read more