Saxon

The issue here is that the user-supplied configuration-level resolver delegates to the StandardURIResolver, which in turn delegates to the user-supplied configuration-level resolver.

I'm not sure how realistic this problem is, but on balance, I think it's probably better if the StandardURIResolver falls back to the DirectResourceResolver.

Note that the StandardURIResolver only really exists in 11.x for backwards compatibility, because user-written URIResolvers are likely to extend it or delegate to it.