[R-pkg-devel] [FWD] [CRAN-pretest-archived] CRAN submission JuliaConnectoR 0.5.0

On 06/04/2020 11:25 a.m., Stefan Lenz IMBI wrote:

Yes, as I wrote earlier, I would like to imitate the behaviour of

loading an R package

  juliaUsing("SomeJuliaPackage") # exports myJuliaFunction
  myJuliaFunction()

like R:

  library("MyRPackage") # exports myRFunction
  myRFunction()

I could return an environment, such that the call becomes

  attach(juliaUsing("SomeJuliaPackage"))
  myJuliaFunction()

I wouldn't use it that way.  I'd write it as

    sjp <- juliaUsing("SomeJuliaPackage")
    sjp$myJuliaFunction()

This is similar to the advice to use pkg::foo() rather than
library(pkg) 
followed by plain foo() in the code.

Duncan Murdoch

But calling juliaUsing(), as it is now, takes care that if a package

is imported a second time,

the first data base is removed via detach().
This way, users do not have to worry about calling juliaUsing()

mutliple times in a script, same

as R users don't have to worry about calling library() multiple

times.

If you call the code with attach() multiple times and do not detach,

you get your screen cluttered with

warnings "xxx is masked by xxx".
So I would say it would decrease user-friendliness to return an

environment.

I also want to make explicit, that the call to attach
occurs only once in my code, after creating the environment:

  envName <- paste0("JuliaConnectoR:", absoluteModulePath)
  if (envName %in% search()) {
  detach(envName, character.only = TRUE)
  }
  attach(funenv, name = envName)

This code is only called by juliaImport() and juliaUsing(), which

aren't called by any other function of

the package
and are supposed to be called directly by the user.

Stefan
  
----------------urspr?ngliche Nachricht-----------------
Von: Duncan Murdoch [murdoch.duncan at gmail.com]
An: Dirk Eddelbuettel [edd at debian.org], Ben Bolker

[bbolker at gmail.com]

Kopie: List r-package-devel [r-package-devel at r-project.org]
Datum: Mon, 6 Apr 2020 11:00:09 -0400
-------------------------------------------------
  
  

On 06/04/2020 10:49 a.m., Dirk Eddelbuettel wrote:

On 6 April 2020 at 08:38, Ben Bolker wrote:
| Just reply to the CRAN maintainers and explain this situation.

It?s

| slightly buried, but the e-mail you received does say:
|
| > If you are fairly certain the rejection is a false positive,

please reply-all to this

| > message and explain.

True, but this misses the "Letter of the law" versus the "Spirit of

the law".

It might be worth mentioning that use of attach() is seen, to find

one poor

analogy, pretty much like use of global variables these days. "Just

because

you could does not mean you should".

See e.g. one of the first google hits for 'r do not use attach'

here:

https://stackoverflow.com/questions/10067680/why-is-it-not-advisable-to-use-attach-in-r-and-what-should-i-use-instead

I don't have a strong opinion on this: the proposed use seems to be

no

worse than library() or require(). Those are fine for users to use,

but

are discouraged in a package. If the attach() never happens without

an

explicit request from the user (and that's what it sounds like), I'd

say

it's probably okay.

However, there is an easy workaround: just return the environment
without attaching it. Then the user has the choice of attaching it,

or

using it as a prefix when they call the functions in it. So it's not

as

though this will destroy the utility of the package if Stefan isn't
allowed to call attach().

Duncan Murdoch