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

[Georgi Boshnakov]

One way to avoid burying the conditional deep into the code is to put it in .onLoad(). When the author of a dependency informed me that from v.2.0.0  "as.polylist would be renamed I put the following in .onLoad():

.onLoad <- function(libname, pkgname){
    if (utils::packageVersion("PolynomF") >= "2.0.0") {
        assign("as.polylist", PolynomF::as_polylist, envir = topenv())
    }
    ## add other renamed functions here

    NULL
}

This still raises a NOTE but is a change in a single place.


Georgi Boshnakov


-----Original Message-----
From: R-package-devel <r-package-devel-bounces using r-project.org> On Behalf Of Duncan Murdoch
Sent: 21 February 2021 19:43
To: Gábor Csárdi <csardi.gabor using gmail.com>
Cc: R Package Development <r-package-devel using r-project.org>
Subject: Re: [R-pkg-devel] Support for several versions of another package

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

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