[R-pkg-devel] cross-ref possible ext.pkg's --not mentioned in DESCRIPTION file-- in non-code sections in .Rd files

[Andrew Simmons]

Packages in Suggests and Enhances do not create a circular dependency, only
the packages in the Depends and Imports need to be installed at INSTALL and
loaded at load time. Packages in Suggests and Enhances are only needed at
check time, and even then it's more of a desire to be loaded than actually
needing to be loaded.

I would just put them in Suggests or Enhances

On Mon, Nov 7, 2022, 11:10 Peter Ruckdeschel <peter.ruckdeschel using web.de>
wrote:

> Hi,
>
> triggered by some new NOTEs uncovering infallacities in my packages on
> CRAN, I stumbled upon
>
> Result: NOTE     Undeclared packages ‘distrMod’, ‘RobAStBase’ in Rd xrefs
>
> which is issued in R-devel-linux-x86_64-fedora-clang (but not otherwise).
>
> Digging into it, this comes from a text in a \seealso section where
> through something like
>
> \code{\{link}[<ext.pkg>]{<generic>}
>
> we want to link to a method provided in some extension package <ext.pkg>
> for a generic
> <generic> documented in Rd-file of the current package.
>
> In this case, we intentionally do not have <ext.pkg> in any of the entries
> "Depends", "Suggests",
> "Imports", "Enhances" in the DESCRIPTION file, as <ext.pkg> is neither
> needed visible for the
> user, nor for the code in the current package nor for testing code nor for
> example code and vignettes
> of the current package, and because having it in "Suggests" would produce
> a circular dependence
> as <ext.pkg> has the current package in its "Imports" section.
>
> Of course, in "Writing R extesions" we find that
>
> "Packages referred to by these ‘other forms’ should be declared in the
> DESCRIPTION file, in
>    the ‘Depends’, ‘Imports’, ‘Suggests’ or ‘Enhances’ fields. "
>
> so I am aware that this is my fault, as I use these 'other forms'  without
> declaration in the DESCRIPTION file.
> Now I guess I could wrap my conditional cross-ref into some R-code,
> testing whether <ext.pkg> is available,
> i.e., something like
>
> \Sexpr[eval=TRUE,stage=render,results=text]{if("<ext.pkg>" %in%
> installed.packages()[,1] )
>   cat("\\code{\\{link}[<ext.pkg>]{<generic>}") else cat("<generic> from
> package \\pkg{<ext.pkg>})
>
> and so produce the link only if <ext.pkg> is installed at rendering time,
> but I would guess such a
> conditional linkage would be something which could be of interest to a
> broader scope of R-package
> developers and hence could and should be implemented in a less cumbersome,
> and more
> efficient way.
>
> Any suggestions welcome,
> best, Peter
>
> --
> %******************************************************************
> % Prof. Dr. Peter Ruckdeschel
> % Institut fuer Mathematik, Fakultaet V - Mathematik und
> Naturwissenschaften
> % Carl von Ossietzky Universitaet Oldenburg,
> % Postfach 5634,  26111 Oldenburg
> % Office: Wechloy W1 02-227 Tel: +49 (0)441 798-3240  Fax: +49 (0)441
> 798-193240
> %peter.ruckdeschel using uni-oldenburg.de
> %http://www.uni-oldenburg.de/peter-ruckdeschel
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