Disallow page from being its own parent

[mtekk]

I noticed this in the 2.7-hemorrhage branch that the dashboard page editor allows you to set the current page as its own parent. If this happens, many things break as PHP enters an infinite query loop. Two things should be done, not show it in the edit page. Additionally, when reading the parent_id, it should be checked to make sure it is not the same as the current page's ID this prevents the infinite loop from ever occurring from this condition. This was observed in r8822.

Looks like categories have this same problem in r8841. I'm going to make some patches for this.

Ok for the page problem it looks like wp_dropdown_pages() is being called now instead of using parent_dropdown() and some surrounding code. If parent_dropdown is being depreciated, then wp_dropdown_pages() is going to need to be passed the excluded pages (which will have to be determined before calling it). It looks like even though it is supposed to be passed $post, $post ends up being NULL (so it does not even select the current parent page if there is one).

I'm opening a new ticket for a similar problem with categories as I found the problem exists in 2.6.1.

wp_dropdown_pages() is more efficient than parent_dropdown() so 2.7 switched to it. parent_dropdown() will be deprecated. This definitely hasn't had enough testing since the switch. Thanks for looking into it.

As of [9188] this seems to be fixed.