S4 NAMESPACE method imports and exports do not include (promoted?) generics
tar of Pkgs A, B, C attached. Martin
On 12/15/2011 03:34 PM, Martin Morgan wrote:
In
> R.version.string
[1] "R Under development (unstable) (2011-12-15 r57901)"
section 1.6.6 of 'Writing R Extensions' says
Note that exporting methods on a generic in the namespace will
also export the generic, and exporting a generic in the
namespace will also export its methods.
and
Note that importMethodsFrom will also import any generics defined in
the namespace on those methods
However, if PkgA promotes 'unique' to a generic and exports that
DESCRIPTION:
Imports: methods
R/f.R:
setGeneric("unique")
NAMESPACE:
export(unique)
and PkgB creates and exports a method on unique
DESCRIPTION
Imports: methods, PkgA
R/f.R:
setClass("B", representation(b="numeric"))
setMethod(unique, "B",
function(x, incomparables=FALSE, ...) unique(x at b))
NAMESPACE:
importFrom(PkgA, unique)
exportClasses(B)
exportMethods(unique)
and PkgC wants to import PkgB's classes and methods
DESCRIPTION
Imports: methods, PkgB
R/f.R
cunique <- function(x) unique(x)
NAMESPACE
importMethodsFrom(PkgB, unique)
export(cunique)
then
(a) the 'unique' generic is not available to the user of PkgB
> library(PkgB)
> unique(new("B", b=1:5))
Error in unique.default(new("B", b = 1:5)) :
unique() applies only to vectors
and (b) the generic has not been imported to PkgC's namespace
> cunique(new("B", b=1:5))
Error in unique.default(b) : unique() applies only to vectors A workaround is for PkgB to also export(unique), and for PkgC to also importFrom(PkgA, unique), but is this the intention? This is arising from Bioconductor efforts to place commonly promoted functions and S3 classes into a single package, to avoid conflicts when the same function is promoted independently by several packages. Martin
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