[R-pkg-devel] Force namespace prefix for a loaded package function

http://www.keittlab.org/

On Mon, Jun 27, 2016 at 10:19 AM, Duncan Murdoch <murdoch.duncan at gmail.com

wrote:

On 27/06/2016 11:08 AM, Tim Keitt wrote:

http://www.keittlab.org/

On Mon, Jun 27, 2016 at 3:22 AM, Joris Meys <jorismeys at gmail.com> wrote:

If you want to call a non exported function, you need three colons

X:::f ()

And frankly, that is a bad idea.

I think you missed the point (and stated the obvious).

A well-designed namespace feature would give control of imports to the
code
user, not the code writer.

Right now, I have to avoid all the function names in base because I will
cause a collision. If I want to have an "options" function in my
package, I
have to make it "pkgname_options" rather than pkgname::options, which is
greatly preferable and would allow the user to decide whether they want
to
import it and then simply use "options" and "base::options".

I've always considered this all-or-nothing approach to imports a bug in
the
implementation of namespaces in R. I was trying to suggest that it be
fixed. (Probably should have sent this to r-devel actually.)

The base package is special, but for all other packages there's no
"all-or-nothing" approach to imports, so your statement about a function
named "options" doesn't really make sense.  If you want to do that, just do
it, and other packages that prefer your implementation to the base one can
import just that one function, or do the import at run time by calling it
as pkgname::options().

I know that. I mean for someone writing a script, not a package.

Its all good for package writers. Its quite simple to control imports
there. But not so much for someone using the package in R to write a
script. You either go with package_name::object for everything or you call
"library" and you get everything the packager exported.

It would be nice to 1) be able to hold back some functions from being
fully exported in a package and (maybe or) 2) extend the functionality of
the NAMESPACE file to the user session via a set of functions.

Does that make any more sense?

THK

Duncan Murdoch

THK

Cheers
Joris
On 26 Jun 2016 19:37, "Tim Keitt" <tkeitt at utexas.edu> wrote:

It would be rather nice if we could define functions in our packages

that

must be called with the namespace prefix.

I'd like to do

#' @protected (or some such)
f = function(...) list(...)

in package scope and then

library(x)
f(1)             # fails
x::f(1)         # succeeds

Currently unless I am missing something, a function is either

exported to

global scope or not available. This could be done if package loading

made

two environments, one in the path and another not in the path, and

then

have the namespace prefix search both in succession.

Yes, you could do

#' @export
x_f = function(...) list(...)

library(x)
x_f(1)

but I would prefer reusing the namespace prefix syntax.

This would also avoid name collisions between package, which ideally

is

the
purpose of a namespace.

I suppose also you could make two packages and list one in Imports:

but I

find that less satisfying because it requires a different namespace
prefix.

Or am I missing something obvious here.

THK

http://www.keittlab.org/

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