has_author() or by_author()

I’m looking for a has_author() conditional function. Yes, I’ve already read the other thread on this topic, but that solution isn’t sufficient for me, because I’m needing this to control widget visibility through Widget Logic (or something similar).

There’s an example on the conditional functions page that says that this will work:

is_single() && is_author(‘authorname’)

But that doesn’t work. In fact, I don’t see how it could ever possibly work, since is_author() looks for an author archive page.

This seems like such an obvious, useful and simple thing to add to core for multi-author blogs. I’m willing to make a small contribution to someone who can code it and contribute it to core.