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

[Sebastian Meyer]

Am 16.12.20 um 18:00 schrieb Neal Fultz:
> IIRC some packages use get() instead of double-colon to suppress the NOTE.

I'd discourage from using get() because you could (accidentally) access
even unexported objects from another namespace. There is

getExportedValue(ns, name)

to avoid that. However, its help page describes it as an internal
function, so I'm not sure if that would be any better. "::" access is
also faster, especially as of the next version of R.

Of course, such workarounds should be used with great care as these
checks are usually very valuable to guard against coding errors or warn
about potential changes in the other package's API.

> I would probably ignore it myself.

Yes. FWIW, conditional use of tools::R_user_dir() is allowed according
to the CRAN repository policy:

> For R version 4.0 or later (hence a version dependency is required or only conditional use is possible), packages may store user-specific data, configuration and cache files in their respective user directories obtained from tools::R_user_dir(), provided that by default sizes are kept as small as possible and the contents are actively managed (including removing outdated material). 

Best regards,

	Sebastian Meyer


> 
> On Wed, Dec 16, 2020 at 8:29 AM 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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