[R] Missing link(s) in documentation object

[Jon Olav Skoien]

Hi,

I want to cross-reference from the documentation of pkg1 to pkg2, which 
is imported in the NAMESPACE of pkg1, and under Depends in DESCRIPTION 
of pkg1. According to "Writing R extensions", this can be done by:
\code{\link{foo}}
when foo is an aliased function in the documentation of pkg2. This works 
as it should when I install the package, but when I run R CMD check 
pgk1, I get a warning:

* checking Rd cross-references ... WARNING
Missing link(s) in documentation object 'fooPkg1.Rd'
  foo

I have tried to change the link to
\code{\link[pkg2]{foo}}
\code{\link[pkg:pkg2]{foo}}
None of these works, the first gives a link that leads to an error page, 
and the second one gives a link that does not work at all. I assume this 
is as it should be; foo.Rd does not exist. However, R CMD check does not 
complain about any of these links...

Why does R CMD check warn me against links that work? I think pkg2 is 
not on the search path when looking for cross-references, but why? R CMD 
check continues to run after the warning without any complaints, and all 
tests rely on pkg2. I am quite sure there is something simple that I 
have overlooked, but cannot figure out what it is.

Best wishes,
Jon

Platform etc:
XP SP3, R 2.9-2, Rtools210 (the problem was also there before upgrading 
from R 2.9-1 and Rtools29 )