WordPress admin: show draft pages in page attributes parent page dropdown

Question

For clarity - here is a picture of the box I am talking about in this question:

Background: I have built a relatively complex WP site for a client which is more of a CMS than a blog and relies on a hierarchy of pages being built. (Well, they're actually custom post types with 'hierarchical' => true set)

My question: is it possible to show draft (or pending review) pages in the page attributes 'Parent page' dropdown list? Without this, it means making each page live before the whole section is ready - and that's not a suitable solution.

What I've tried:

• Looking for an action which gets called to build the list (can't find one)
• Looking in the source code for where the list is created (it's built with wp_dropdown_pages which doesn't appear to let you choose the post status)
• Looking for plugins which provide this functionality

Answer 1

Very nice question!

The following does it. One filter is for the edit page screen and the other for the Quick Edit menu.
Tested with a hierarchical custom post type.

add_filter( 'page_attributes_dropdown_pages_args', 'so_3538267_enable_drafts_parents' );
add_filter( 'quick_edit_dropdown_pages_args', 'so_3538267_enable_drafts_parents' );

function so_3538267_enable_drafts_parents( $args )
{
    $args['post_status'] = 'draft,publish,pending';
    return $args;
}