[R-pkg-devel] Support for several versions of another package

[Duncan Murdoch]

On 21/02/2021 12:17 p.m., Gábor Csárdi wrote:
> On Sun, Feb 21, 2021 at 6:05 PM Duncan Murdoch <murdoch.duncan using gmail.com> wrote:
>>
>> On 21/02/2021 9:47 a.m., Iñaki Ucar wrote:
>>> Hi,
>>>
>>> Let's say that pkgA uses pkgB::function1. Then, version 2 of pkgB
>>> removes function1 and exports function2 for the same functionality. So
>>> pkgA does something along these lines:
>>>
>>> if (utils::packageVersion("pkgB") < 2) {
>>>     pkgB::function1()
>>> } else {
>>>     pkgB::function2()
>>> }
>>>
>>> I'd say that there's nothing wrong with this code, and yet checks will
>>> complain about "missing o unexported object" in pkgB, for either
>>> function1 or function2 depending on the version of pkgB that is
>>> available.
>>>
>>> Isn't this a false positive? Or is there a better way of doing this?
>>
>> I'd agree it's a false positive, but I wouldn't expect the check code to
>> be able to interpret the logic.
>>
>> A better way could be to handle it in your NAMESPACE file.  For example,
>> this is legal (if nonsense):
>>
>> if (utils::packageVersion("rgl") < "0.99.0") {
>>          importFrom(rgl, bar = somethingNonexistent)
>> } else
>>          importFrom(rgl, bar = persp3d)
> 
> Isn't this evaluated at install time? I think it is, and then you
> would need to potentially reinstall the package when you update rgl,
> which is not quite ideal, because it is easy to miss it, and then
> you'll get runtime errors.

Yes, you're right, I didn't know that.  That's not as useful.

Duncan Murdoch