[R-pkg-devel] Extending an S3 method, but putting the package in Suggests?

[David Hugh-Jones]

Hi Martin,

Thanks. I figured that out after trying it myself, so I didn't do that.
OTOH, a whole new package just so I can extend a method... I feel that life
is too short. So, I cut the Gordian knot and just wrote as_FlexTable
instead of as.FlexTable, and skipped the whole inheritance issue.

Cheers,

David


On 14 March 2017 at 16:35, Martin Maechler <maechler at stat.math.ethz.ch>
wrote:

> >>>>> David Hugh-Jones <davidhughjones at gmail.com>
> >>>>>     on Tue, 14 Mar 2017 09:26:49 +0000 writes:
>
>     > Just out of interest, what would happen if I used the hacky solution
> of
>     > simply  exporting my own method like:
>
>     > as.FlexTable <- function(x, ...) UseMethod("as.FlexTable")
>
>     > I am fairly sure you will tell me that fire and brimstone will rain
> down…
>     > But it sure seems simple  compared to writing another package and
> getting
>     > it on CRAN...
>
> no fire etc, but pretty close ;-)
>
> You will have two (internal) methods tables for as.FlexTable,
> one in ReporteRs, one in your package, and from a user point of
> view there's a deep abyss in functionality between working with
>
>   require(ReporteRs); require(huxtable)
>
> and working with
>
>   require(huxtable); require(ReporteRs)
>
> This is undesirable and error prone and can be resolved by
> correct imports as those mentioned.
>
> Martin
>
>     > David
>
>     > On Tue, 14 Mar 2017 at 09:06, Martin Maechler <
> maechler at stat.math.ethz.ch>
>     > wrote:
>
>     >> >>>>> David Hugh-Jones <davidhughjones at gmail.com>
>     >> >>>>>     on Tue, 14 Mar 2017 02:46:35 +0000 writes:
>     >> >>>>> David Hugh-Jones <davidhughjones at 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
>     >>
>     >> --
>     > Sent from Gmail Mobile
>
>     > [[alternative HTML version deleted]]
>
>

	[[alternative HTML version deleted]]