Adding methods to another package's R6 class: how to document?

[hongooi73]

R6 has a nifty feature where you can add new members to an existing class via set(). You can even do this to a class exported by a different package, which is very useful indeed.

For example, in package A:

#' @export
myclass <- R6::R6Class("myclass",
    public=list(
        f=function(x) { ... }
))

And in package B:

# modifying objects exported by another package must be done at runtime
.onLoad <- function(libname, pkgname)
{
    A::myclass$set("public", "g", overwrite=TRUE,
        function(y) { ... }
}

Now you can do something like

library(A)
library(B)
obj <- A::myclass$new(...)
obj$g(y=42)  # method defined by package B

How should we document the new method added by B?

[hadley]

Effectively a duplicate of #388, since we don't have any way to document any R6 class.