[Rd] problem with vignettes when S4 classes in packages overlap

Duncan Murdoch murdoch.duncan at gmail.com
Wed Sep 19 02:53:35 CEST 2012

On 12-09-18 7:50 PM, Spencer Graves wrote:
> On 9/18/2012 4:23 PM, Duncan Murdoch wrote:
>> On 12-09-18 5:40 PM, Paul Gilbert wrote:
>>> ( A similar problem is also reported by Sebastian P. Luque with
>>>      library(maptools)
>>>      library(trip)
>>> in the vignette as below ).
>>> I am writing a vignette which loads RMySQL and RPostgreSQL. This
>>> produces the warning:
>>> Loading required package: DBI
>>> Warning in .simpleDuplicateClass(def, prev) :
>>>      A specification for class “dbObjectId” in package ‘RPostgreSQL’
>>> seems
>>> equivalent to one from package ‘RMySQL’ and is not turning on duplicate
>>> class definitions for this class
>>> This can be reproduced by running
>>>      R CMD Sweave --pdf Atest.Stex
>>> where the file Atest.Stex has the lines
>>> \documentclass{article}
>>> \usepackage{Sweave}
>>> \begin{document}
>>> \begin{Scode}
>>> library("RMySQL")
>>> library("RPostgreSQL")
>>> \end{Scode}
>>> \end{document}
>>> These warnings only happen in a vignette. They are not produced if the
>>> lines are entered in an R session.
>>> (Using R version 2.15.1 (2012-06-22) -- "Roasted Marshmallows" on Ubunt
>> You'll get the warning in a regular session if you set
>> options(warn=1).  I think Sweave is probably doing this so that
>> warnings show up around the time of the chunk they correspond to. It
>> does it in the command line version, but not in the Sweave() function
>> (which would save them up to the end).
>> I don't know if the warning is something you should worry about or not.
>         On August 30, 2012, CRAN maintainers rejected the latest version
> of "fda", and I understood them to say it was rejected because the
> current CRAN policy did not accept packages reporting either "Notes" or
> "Warnings".  As part of my efforts to comply with this, I started the
> thread on [Rd] subject:  "if(--as-cran)?"  I added a function "CRAN" to
> "fda", and I thought someone had added a more general function to the
> development version of R. Unfortunately, I can't find documentation of
> that more general function now.

I don't remember for sure, but I don't think your warning or note was 
the same as Paul's.  Generally it's not a good idea to suppress 
warnings.  Someone should fix things so there's no warning.  I don't 
know if that should be RCore because the methods package is issuing a 
bogus warning, or the maintainer of one of the database packages, or 
Paul.   (From his example, it doesn't look like it should be Paul, 
unless docs somewhere say that RMySQL and RPostgreSQL can't be used 

In general, as a package user, I don't want people to be able to 
suppress checks on CRAN.  I want things fixed.

So I am pretty sure there won't ever be a reliable "CRAN-detector" put 
into R.  It would devalue the brand.

Duncan Murdoch

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