On Thu, 5 Nov 2015 08:32:41 +0100, Sönke Ludwig wrote:

A trick that is usually possible is to make the session argument have a
default value (= Session.init) and put it in the interface like that.
The catch is that default and Nullable parameters are not properly
handled by the JS client, yet. I'll open a ticket for that.

https://github.com/rejectedsoftware/vibe.d/issues/1320