Re R CMD check checking in development version of R

Yes, Depends certainly has a role. The ability of one package to
automatically provide all the facilities of another package to the
user is important. There are many situations where the functionality
you want to provide to the user is split among multiple packages.

For example,

1. xts uses zoo and the user ought to be able to use all the
functionality of zoo when they issue a library(zoo) call.  The
alternatives are that the user must tediously issue library(zoo) every
time they issue library(xts) or else that the zoo code be copied or
partially replicated into xts which would be undesirable
maintenance-wise.

2. Another example is sqldf.  The user wants to be able to use fn$ and
other string manipulation functions in gsubfn when using sqldf in
order to perform string substitution on the SQL statement.  Also its
desirable to be able to directly access sqlite which means the user
needs access to RSQLite.

3. At one time one could just issue library(ggplot2) but now that
ggplot2 does not use Depends for scales one annoyingly needs to issue
library(scales) if one wants to specify a scale.   I use ggplot2
enough that I can remember it despite the ongoing annoyance but I
would hate to think that every package with split functionality
suddenly adds such onerous requirements onto all its users.  (I am not
really picking on ggplot2 which is a very nice package - just this one
aspect.)

I am not sure but there might be additional problems if the secondary
package defines an S3 generic that the primary package needs to use if
one does not use Depends.

Re R CMD check checking in development version of R

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