[R-pkg-devel] Dependency needs to be loaded manually even its specified in the package

[Duncan Murdoch]

On 18/09/2020 12:38 p.m., Nuria Perez-Zanon wrote:
> Dear all,
> 
> I am maintaining a package call CSTools which is aimed for
> post-processing climate simulations.
> 
> The package is already published on CRAN with all dependencies correctly
> state in DESCRIPTION, NAMESPACE and roxygen2 headers.
> 
> However, when using one specific function which depends on 'qmap'
> package, I should loaded both packages by executing:
> 
>       library(CSTools)
>       library(qmap)
> 
> In case I don't load the second library, I get the error
> 
> Error in doQmap(x = sample_cor, fobj = adjust, ...) :
>     doQmap not defined for class(fobj) ==fitQmapQUANT
> 
> Has anyone an idea for needing to manually load a dependency? I provide
> a code below if someone wants to test it.
> 
> Thanks in advace,
> 
> Núria
> 
> P.S.: Here is the code: library(CSTools) exp <- lonlat_data$exp
> obs <- lonlat_data$obs
> res <- CST_QuantileMapping(exp, obs)
> 
> 

That's a design flaw in the doQmap function.  It looks like this:

function (x, fobj, ...)
{
     cc <- class(fobj)
     ffun <- substring(cc, 4, nchar(cc))
     ffun <- paste("do", ffun, sep = "")
     test <- sapply(ffun, exists, mode = "function")
     if (all(test)) {
         ffun <- match.fun(ffun)
     }
     else {
         stop("doQmap not defined for class(fobj) ==", class(fobj))
     }
     ffun(x, fobj, ...)
}

There are at least a couple of errors there:

- It appears to assume class(fobj) is a single element character string. 
  This wouldn't have caused your problem, but it will probably cause 
problems sometime..

- It tries to do something like S3 methods dispatch without using S3, by 
looking up "doQmapQUANT" in that line producing "test", but not saying 
where to look for it.  You could probably fix this by adding the envir 
argument to exists() in that call, e.g.

   test <- sapply(ffun, exists, mode = "function", envir = 
parent.env(environment()))

but it would be better to not try to invent a new object system.

Duncan Murdoch