I have a client running WPMU 2.9.1 who's recently starting using the Domain Mapping plugin to map a domain to one of their MU blogs. Overall it's been great. However, there's one weird bug we've run into, and I haven't been able to find guidance anywhere on how to fix it.
They have an old internally-developed plugin that uses WordPress' url_to_postid() function (part of WP_Rewrite, though apparently a fairly obscure part) to take a URL of a post from another of their MU blogs and fetch that post's ID.
The problem is url_to_postid seems not to like URLs that use the mapped domain. When it's passed one of these, it returns nothing, not even a zero/null value/error code/etc.
I've looked high and low to see if there's information anywhere on how the Domain Mapping plugin interacts with WP_Rewrite in general and url_to_postid in particular, but I haven't found anything. So I figured I'd ask the experts :D Any ideas on ways to teach url_to_postid to respect domain-mapped URLs, or, failing that, other approaches I should use to resolve a URL into a post ID?