[R-pkg-devel] Three-argument S3method declaration does not seem to affect dispatching from inside the package.
Hi, Inaki,
On Tue, 2019-05-14 at 12:50 +0200, I?aki Ucar wrote:
The thing is that, in R, "nearer" means "the calling environment" (and then, other things). When you call test_me(), the calling environment for gen() is the package namespace. When you call gen() directly, thenthe calling environment is the global environment. So what happens here follows the principle of least astonishment.
I don't think that we disagree about which environment takes precedence. The issue is whether *within a a given environment*, registration or function naming should take precedence.
The issue here is that you are registering a non-standard name (.gen.formula) for that generic and then defining what would be the standard name (gen.formula) for... what purpose? IMHO, this is a bad practice and should be avoided.
The situation initially arose when I wanted to soft-deprecate calling a particular method by its full name in order to clean up the package's namespace. To use our working example, I wanted calls to gen.formula() to issue a deprecation warning, but calls to gen(formula) not to. The simplest way to do that that I could find was to create a function, say, .gen.formula() that would implement the method and declare it as the S3 export, and modify gen.formula() to issue the warning before passing on to .gen.formula(). Then, direct calls to gen.formula() would produce a warning, but gen(formula) would by pass it.
That is, for a call from inside a package, the order of precedence
would be as follows:
1. S3method() in that package's NAMESPACE.
2. Appropriately named function in that package (exported or
not).
3. Appropriately named function in calling environment (which
may be
GlobalEnv).
4. S3method() in other loaded packages' NAMESPACEs.
5. Appropriately named functions exported by other loaded
packages'
NAMESPACEs.
For a call from outside a package, the precedence is the same, but
1 and 2 are not relevant.
As far as I can tell, this is the current behaviour except for the
relative ordering of 1 and 2.
Nope. Current behaviour (see details in ?UseMethod) is: "To support this, UseMethod and NextMethod search for methods in two places: in the environment in which the generic function is called, and in the registration data base for the environment in which the generic is defined".
Can you be more specific where the sequence above contradicts the current implementation (except for swapping 1 and 2)? As far as I can tell, it's just a more concrete description of what's in the documentation. Best Regards, Pavel
Pavel Krivitsky Lecturer in Statistics National Institute of Applied Statistics Research Australia (NIASRA) School of Mathematics and Applied Statistics | Building 39C Room 154 University of Wollongong NSW 2522 Australia T +61 2 4221 3713 Web (NIASRA): http://niasra.uow.edu.au/index.html Web (Personal): http://www.krivitsky.net/research ORCID: 0000-0002-9101-3362 NOTICE: This email is intended for the addressee named and may contain confidential information. If you are not the intended recipient, please delete it and notify the sender. Please consider the environment before printing this email.