Export a list of functions with roxygen2

问题

Problem — I want to export a list of functions as part of an R package, ideally using roxygen2.

To be more precise, I want to export the functions in the list, rather than the list itself. For example, consider a list of functions that are generated as closures, like so:

addval <- 1:100
fns <- lapply(addval, function(y) {force(y); function(x) x + y})
names(fns) <- paste0("add_", addval)

Then the problem is to bind the functions (using the same names in fns, for instance) to the package environment, and then include them among the exported functions of the package.

Binding the functions to the package environment can be done easily enough; one way would be

for (nm in names(fns)) assign(nm, fns[[nm]])

But is it then possible to use roxygen2 tags to export the functions add_1, add_2, etc.?

More to the point: I would like roxygen2 to continue managing the NAMESPACE file for me, and would prefer not to have to write export() calls, directly. The only way I can see doing that is by writing code to generate boilerplate like

#' @export add_1
NULL

#' @export add_2
NULL

# ...

or better

#' @export
add_1 <- fns[["add_1"]]

#' @export
add_2 <- fns[["add_2"]]

# ...

(and forgo the above for-loop).

Does roxygen2 already have a facility equivalent to such boilerplate generation, or would I have to provide this facility myself?

I have in mind such a facility being expressed more succinctly as

#' @exportObjects names(fns)
NULL

where the tag @exportObjects would interpret its "argument" as a character vector of names of objects to export.

Update

roxygen2 6.0.1+ solves this problem with a new @evalNamespace tag, which allows you to insert literal entries in the NAMESPACE file:

ns_export <- function(nms)
  sprintf("export(%s)", paste(nms, collapse = ","))

#' @evalNamespace ns_export(names(fns))

Using the tag @evalNamespace is safer than using a exportPattern() directive, because in using the latter, one has to be vigilant against accidentally naming an object in the package namespace that matches the regex.

回答1:

You can use the @rawNamespace tag in recent roxygen2, this allows using arbitrary syntax valid in a NAMESPACE file, including exportPattern():

#' @rawNamespace exportPattern("^add_.*$")

来源：https://stackoverflow.com/questions/39917807/export-a-list-of-functions-with-roxygen2

标签

roxygen2

r-package