Devin Price

Okay, tested a few more things. Try this one:

function prefix_transition_post_status( $new_status, $old_status, $post ) {

	$stickies = get_option( 'sticky_posts', array() );
	$new_sticky = isset($_POST['sticky']) && $_POST['sticky'] == 'sticky';

	if ( 'publish' == $new_status && ( in_array( $post->ID, $stickies ) || $new_sticky ) ) {
		update_option( 'sticky_posts', array( $post->ID ) );
	}

}
add_action( 'transition_post_status', 'prefix_transition_post_status', 10, 3 );

This will catch when a new post is published or a scheduled post is published.

However, if you have other scheduled posts that are also marked sticky, it will remove the sticky marking from those. Very annoying that WordPress puts this in an option table rather than just post meta.

The only workaround I can think of for that is:

1) Check if there are any posts in the $stickies array.
2) If so, remove the current $post->ID from that array if it exists
3) Query all the remaining sticky posts
4) If remaining sticky posts are not published, add them to a clean $new_stickies array
5) Add the current post to the $new_stickies array
6) update_option( ‘sticky_posts’, $new_stickies );

Make sure that is all wrapped inside the “if” conditional, so it only gets run when a new sitcky is being published.