[Rd] Namespace dependency not required

Patrick Giraudoux patrick.giraudoux at univ-fcomte.fr
Sun Mar 18 16:08:29 CET 2012

Le 18/03/2012 14:57, Uwe Ligges a écrit :
> On 18.03.2012 11:21, Patrick Giraudoux wrote:
>> Hi,
>> I am working at adding namespace to my packages, carefully following the
>> doc "Writing R extensions" and some threads on the web. However I cannot
>> find clear explanation about how to best deal with the import or
>> importFrom functions in the name space. To make it short:
>> To declare dependencies in the description file either after Depends:
>> (packages including functions that are called from a package function)
>> or after Suggests: (packages that are called eg from the doucmentation
>> examples), works well. In this case one does not need to declare import
>> in the namespace file.
>> However, declaring dependencies sometimes for using only one function in
>> a given package looks a bit over the top, and I though I could use
>> importFrom in the namespace to deal with that. So removing the
>> corresponding declaration in Depends (description file) and declaring
>> eg  importFrom(splancs, inout) in the namespace always led to:
>> * checking package dependencies ... ERROR
>> Namespace dependency not required: 'splancs'
>> Same thing with import(sp). I have the same trouble if I do not remove
>> the declarations in Depends.
>> So, I can hardly follow the meaning of the "Writing R extension" doc:
>> Packages implicitly import the base namespace. Variables exported from
>> other packages with namespaces need to be imported explicitly using the
>> directives |import| and |importFrom|. The |import| directive imports all
>> exported variables from the specified package(s). Thus the directives
>>        import(foo, bar)
>> specifies that all exported variables in the packages *foo* and *bar*
>> are to be imported. If only some of the exported variables from a
>> package are needed, then they can be imported using |importFrom|. The
>> directive
>>        importFrom(foo, f, g)
>> specifies that the exported variables |f| and |g| of the package *foo*
>> are to be imported.
>> Can anybody tell us the conditions for which import and importFrom
>> commands should be used in the NAMESPACE rather than in the Depends and
>> Suggests declarations of the description file, and the conditions of
>> their applicability (without error message... eg with a working 
>> example) ?
> If you import from another namespace (which is the recommended way 
> rather than just relying on search order), do not forget to declare it 
> as "Imports" in your DESCRIPTION file. Your package depends on the 
> other one: It could not be loaded without having the other one 
> installed now.
> Uwe Ligges

OK. got it (more or less).

With this in the description file:

Depends: boot (>= 1.3-4), nlme(>= 3.1-64), rgdal (>= 0.7-8), sp (>= 
0.9-97), spdep (>= 0.5-43), splancs (>= 2.01-31)

importFrom(splancs, inout) is accepted in the NAMESPACE file and I have 
no error message with rcmd check.

Irr works also with:

Depends: boot (>= 1.3-4), nlme(>= 3.1-64), rgdal (>= 0.7-8), sp (>= 
0.9-97), spdep (>= 0.5-43)
Imports: splancs (>= 2.01-31)

Practically, I a am safe (thanks a lot), but I am however still hungry 
to learn a bit more. I hardly understand what R does when reading the 
suggests and imports in the DESCRIPTION file compared to what it does 
reading the NAMESPACE (my mistake was to believe that one was a 
substitute for the other). From a practical point of view, why is it 
important to use import or importFrom in the NAMESPACE when everything 
looks like working well when declarations are done in the DESCRIPTION 
file only (eg in depends or imports)?  It is not crystal clear to me 
even reading carefully "Writing R extension". DESCRIPTION file is used 
to get the "list of packages that will be attached (...) before the 
current package" (indeed, now, I no longer needs to use 'require' within 
my package functions). In simple words, what may add the NAMESPACE to 
that ?

Apologize to be so poorly aware (= so much stupid) about the role of 
each of those declaration spaces.



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