Wow. This is interesting. I thought that absolute URL support was only for proxies, but the spec you quote says clearly it should be supported as a transition towards always specifying the full URL. I guess they want to get rid of the Host: header?

In any case I would worry (a bit) that this might cause security issues if implemented as naively as shown in your patch -- the other components of the URL should probably be validated against the configuration of the server. Also I am wondering whether specifying a different port or protocol (e.g. HTTPS) should be allowed or not, and what to do with extraneous parts of the path (in particular the "#fragment" identifier). You should probably also be careful with path-less domain names -- IIRC some URL parsers produce "" as the path for e.g. "http://python.org".

Finally, AFAIK the HTTP 1.1 standard is full of ideas that few server implementations support, for various reasons, and it's possible that a future standard actually rescinds (or discourages) some features. Have you asked for the status of this particular feature?