Using un-exported function from another R package?

Question

I often use utility type functions from other packages that are un-exported: pkg:::fun(). I am wondering if I can use such a function within new functionality/s

Answer 1

• Summarising comments from @baptise, and etc...:

• ::: not allowed on CRAN, so options:

  1. ask author to export it so you can use it in your package via standard imports or suggests.
  2. copy / lift a version of it and clearly cite within your package.

Answer 2

Another trick is using getFromNamespace():

fun <- utils::getFromNamespace("fun", "pkg")

The only advantage over ::: is that you don't get any NOTEs and it's allowed on CRAN. Of course, this is not good practice as a hidden change in pkg can break your package.

Note: With roxygen2 you have to add the utils package to the Imports field of your DESCRIPTION file to fulfill CRAN's requirements. Alternatively, you can put it in your NAMESPACE manually.