R package dependency issues when namespace is not attached

On Sun, May 13, 2012 at 10:14 AM, Uwe Ligges

I do not see any problem in R. If someone is going to import a Namespace, he
or she has to do that via import directives in the NAMESPACE file. If
someone is going to have a package on the search path, he or she has to
require() it. The DESCRIPTION file is used to derive the dependency
structures among packages for installation order, check order etc.

I am not sure everyone is aware of this. Many package authors seem to
be assuming that having a package in the Depends field of the
DESCRIPTION is a sufficient condition for having the dependency
package available at runtime, regardless of how the function is
invoked by the user. I think this is the usual meaning of a
dependency. There are a lot of packages on CRAN that use Depends and
are not explicitly importing anything. Among others, this holds for
any package without a NAMESPACE file.

Also looking at the definition of the 'Depends' field in the 'writing
r extensions' manual there is not a single hint that Depends is not
sufficient for having the package available at runtime, and any
function that is used should still be manually imported or required()
as you suggest.