[R-pkg-devel] Accessing features in R4.0.

[brodie gaslam]

I don't know if this will work in your case (or even if it is a good
or bad thing to do), but backports conditionally exports the function
in question, e.g.:

https://github.com/r-lib/backports/blob/master/R/lengths.R

So in that example their implementation of a function not available
in R < 3.2.0 is presumably only exported for those versions of R.
You could try something similar, although I make no guarantees
on whether this is considered proper or not.  It _seems_ like
a clean solution to me, but I have no experience putting any
logic in the namespace file.

WRE does show something very similar, so this might be okay:

https://cran.r-project.org/doc/manuals/R-exts.html#Registering-S3-methods

Best,

B.



On Wednesday, December 16, 2020, 11:29:08 AM EST, Colin Gillespie <csgillespie using gmail.com> wrote: 





Hi,

I'm planning on using the tools::R_user_dir function in a package. But
for obvious reasons, I don't want to set the dependency on R 4.

My code is basically

if (as.numeric(R.version$major) < 4) # do something
else tools::R_user_dir("oysteR", which = "cache")

When checking on win-builder R3.6 I get the note

* checking dependencies in R code ... NOTE
Missing or unexported object: 'tools::R_user_dir'

## Question

Is my code correct and can I ignore this note?

Thanks

Colin


Dr Colin Gillespie
http://www.mas.ncl.ac.uk/~ncsg3/

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