Variable permalinks

I’m working on migrating a blog. The old one had a pretty good search engine footprint, so we’ve set up redirection to handle the transition to a new domain. I set up the permalink structure to match their old site; the structure is /article/[slug]. However, it seems that their old (custom) blogging platform served pages before a certain date without the “/article” in the front; now, clicking these links in search results are giving 404’s at the new blog.

I’d thought about changing the posts to pages (which would fix this problem), but they already have a nice page structure set up; so, I don’t think that’s an option.

What I think would work is, if WordPress looks for what it thinks is a page and can’t find it, it would try again with “/article” on the front of it. However, in digging into the code, it seems that the 404 status is determined even earlier, when it spins through rewrite rules from the database.

Would it be feasible to put a small hack in there to append “/article” to the preg_match target? I’m still not sure how I could do that for these posts without messing up pages, as the 404 is determined in the WP class, and not WP_Query. If I could make it find the post slug, the canonical redirect should handle actually redirecting to the new permalink format.

Any constructive suggestions would be appreciated. 🙂

Daniel