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

[Duncan Murdoch]

On 27/06/2016 5:46 PM, Tim Keitt wrote:



http://www.keittlab.org/

On Mon, Jun 27, 2016 at 10:19 AM, Duncan Murdoch
> 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 > 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?


It makes a little more sense, but it's still not correct.  If you want 
to do the equivalent of importing foo::options, just add the line


options <- foo::options

at the start of your script.  This "imports" that one function, and 
nothing else from the foo namespace.


It has the side effect of leaving the options object in the current 
workspace afterwards.  If that concerns you, use local():


local( {
  options <- foo::options
  # Lots of calculations, computing result
  result
})

Duncan Murdoch




THK



Duncan Murdoch


THK



> Cheers
> Joris
> On 26 Jun 2016 19:37, "Tim Keitt" > 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/
>>
>> [[alternative HTML version deleted]]
>>
>> __
>> R-package-devel@r-project.org
 mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-package-devel
>>
>

[[alternative 

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

[Tim Keitt]

http://www.keittlab.org/

On Mon, Jun 27, 2016 at 3:22 AM, Joris Meys  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.)

THK



> Cheers
> Joris
> On 26 Jun 2016 19:37, "Tim Keitt"  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/
>>
>> [[alternative HTML version deleted]]
>>
>> __
>> R-package-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-package-devel
>>
>

[[alternative HTML version deleted]]

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

[Tim Keitt]

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/

[[alternative HTML version deleted]]

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