R devel - Sep 2013 - Importing function that is previously imported by other package

Dear developeRs,

I encounter the following problem: in the current version of my package 
FrF2, certain calls to a functioni do not work when package combinat is 
loaded, because function combn from combinat masks the function from 
utils that my package uses.
I tried to solve this issue by importing function combn into the 
namespace of FrF2; I don't need to export it, I just want to use it 
internally in the package; I could of course find all occurrences and 
replace them with utils::combn, but I thought that the namespace 
solution would be more elegant, faster, and in the spirit of R 
programming. The fix was successful: the installed package works with 
combinat on the search path.

However, when installing or loading the modified FrF2, I now get the 
warning "replacing previous import by utils::combn when loading
'FrF2'"
(that's on R-devel, on production R the wording is slightly different, 
but there is also a warning). There is no warning from R CMD check, 
however. In case this is relevant: None of the packages in my
"Depends"
list mentions "utils" under depends, one of the packages FrF2 depends
on
also imports from utils, including utils::combn.

Shouldn't it be possible to have several packages IMport a function of 
the same name without a warning?

Best, Ulrike

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## Prof. Dr. Ulrike Groemping
## FB II
## Beuth University of Applied Sciences Berlin
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On 13-09-06 5:36 AM, Ulrike Gr?mping wrote:
> Dear developeRs,
>
> I encounter the following problem: in the current version of my package
> FrF2, certain calls to a functioni do not work when package combinat is
> loaded, because function combn from combinat masks the function from
> utils that my package uses.
> I tried to solve this issue by importing function combn into the
> namespace of FrF2; I don't need to export it, I just want to use it
> internally in the package; I could of course find all occurrences and
> replace them with utils::combn, but I thought that the namespace
> solution would be more elegant, faster, and in the spirit of R
> programming. The fix was successful: the installed package works with
> combinat on the search path.
>
> However, when installing or loading the modified FrF2, I now get the
> warning "replacing previous import by utils::combn when loading
'FrF2'"
> (that's on R-devel, on production R the wording is slightly different,
> but there is also a warning). There is no warning from R CMD check,
> however. In case this is relevant: None of the packages in my
"Depends"
> list mentions "utils" under depends, one of the packages FrF2
depends on
> also imports from utils, including utils::combn.
>
> Shouldn't it be possible to have several packages IMport a function of
> the same name without a warning?
>
> Best, Ulrike
>
I think we need to see the details.  I don't get those warnings with the 
version on CRAN.  Perhaps you are importing it twice, e.g.

import(combinat)
importFrom(utils, combn)

?

Duncan Murdoch