Why does comments_open() return false when publishing a scheduled post?

Question

My plugin does stuff whenever a post is published and comments are enabled for that post. It works fine when publishing a post as normal, but if a scheduled post is published, it doesn't.

Here's what my code looks like:

function do_stuff( $new_status, $old_status, $post ) {
    global $post;

    if ( !comments_open( $post->ID ) ) {
        return;
    }

    /* do stuff */
}
add_action( 'transition_post_status', 'do_stuff', 10, 3 );

After some debugging, I was surprised to find the problem was comments_open() returning FALSE, every single time a scheduled post was published, regardless of the "Allow Comments" setting.

Why is this happening?

Answer 1

The problem was caused by referencing the global $post object. The global $post has not yet been initialized with the new post's details, so checking to see whether or not its comments are open will always return false at the transition_post_status hook.

The $post variable passed to my do_stuff() function does contain all the correct information about my new post, so I work with it instead. I eventually ended up with something like the following, which functions correctly with both regular and scheduled posts:

function do_stuff( $new_status, $old_status, $post ) {
   if ( $post->comment_status == 'closed' ) {
     return;
   }

   /* do stuff */
}
add_action( 'transition_post_status', 'do_stuff', 10, 3 );