>>>>> David Hugh-Jones <davidhughjo...@gmail.com>
>>>>> on Tue, 14 Mar 2017 02:46:35 +0000 writes:
>>>>> David Hugh-Jones <davidhughjo...@gmail.com>
>>>>> on Tue, 14 Mar 2017 02:46:35 +0000 writes:
> Hi,
> Cross-posted from SO:
>
http://stackoverflow.com/questions/42776058/extending-an-s3-generic-from-an-optional-package
((sent my answer there as well))
> I have a package which provides an as.FlexTable method for its objects,
> extending the S3 generic from the ReporteRs package. So, my NAMESPACE
file,
> generated by roxygen, has lines:
> importFrom(ReporteRs,as.FlexTable)
> ...
> S3method(as.FlexTable,huxtable)
> ...
> export(as.FlexTable)
> I don't much want to put ReporteRs in Imports: in the DESCRIPTION file,
> because it involves a big external dependency on Java. But, when I put it
> into Suggests:, R CMD check gives me errors like "Namespace dependency not
> required".
> Is there anyway I can extend the generic without making a hard dependency?
No. Importing is a hard dependency..
Some people do not import formally but use '<pkgNamespace>::<obj>'
instead, *and* conditionalize their code on the availability of
that namespace.
I don't recommend that at all, and particularly not for
extending a generic.
I recommend you talk with the maintainer of 'ReporteRs':
1) You could use a common (yet-to-create) very small package say
'flexS3generics'
which provides S3 generics (and S4 if ..) you want to use
both, and then both you and her/him import from that mini package.
You'd be both authors of that package.
2) If your package is much smaller (in its footprint, incl
dependencies) than 'ReporteRs' she/he may agree to import the
S3 generic from your package instead of the other way around.
Both are clean solutions,
and both need some time-coordination when releasing to CRAN,
'1)' being easier: Once the 'flexS3generics' is released to
CRAN, change (both) your package(s) to
importFrom(flexS3generics,*) but these changes and CRAN
submissions are then independent of each other.
> Cheers,
> David
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