[Rd] [External] Re: Repeated library() of one package with different include.only= entries

[iuke-tier@ey m@iii@g oii uiow@@edu]

On Thu, 11 Apr 2024, Duncan Murdoch wrote:

> On 11/04/2024 7:04 a.m., Martin Maechler wrote:
>>>>>>> Michael Chirico
>>>>>>>      on Mon, 8 Apr 2024 10:19:29 -0700 writes:
>>
>>      > Right now, attaching the same package with different include.only= 
>> has no
>>      > effect:
>>
>>      > library(Matrix, include.only="fac2sparse")
>>      > library(Matrix)
>>      > ls("package:Matrix")
>>      > # [1] "fac2sparse"
>>
>>      > ?library does not cover this case -- what is covered is the 
>> _loading_
>>      > behavior of repeated calls:
>>
>>      >> [library and require] check and update the list of currently 
>> attached
>>      > packages and do not reload a namespace which is already loaded
>>
>>      > But here we're looking at the _attach_ behavior of repeated calls.
>>
>>      > I am particularly interested in allowing the exports of a package to 
>> be
>>      > built up gradually:
>>
>>      > library(Matrix, include.only="fac2sparse")
>>      > library(Matrix, include.only="isDiagonal") # want: 
>> ls("package:Matrix") -->
>>      > c("fac2sparse", "isDiagonal")
>>      > ...
>>
>>      > It seems quite hard to accomplish this at the moment. Is the 
>> behavior to
>>      > ignore new inclusions intentional? Could there be an argument to get
>>      > different behavior?
>> 
>> As you did not get an answer yet, ..., some remarks by an
>> R-corer who has tweaked library() behavior in the past :
>> 
>> - The `include.only = *` argument to library() has been a
>>    *relatively* recent addition {given the 25+ years of R history}:
>>
>>    It was part of the extensive new features by Luke Tierney for
>>    R 3.6.0  [r76248 | luke | 2019-03-18 17:29:35 +0100], with NEWS entry
>>
>>      • library() and require() now allow more control over handling
>>        search path conflicts when packages are attached. The policy is
>>        controlled by the new conflicts.policy option.
>> 
>> - I haven't seen these (then) new features been used much, unfortunately,
>>    also not from R-core members, but I'd be happy to be told a different 
>> story.
>> 
>> For the above reasons, it could well be that the current
>> implementation {of these features} has not been exercised a lot
>> yet, and limitations as you found them haven't been noticed yet,
>> or at least not noticed on the public R mailing lists, nor
>> otherwise by R-core (?).
>> 
>> Your implicitly proposed new feature (or even *changed*
>> default behavior) seems to make sense to me -- but as alluded
>> to, above, I haven't been a conscious user of any
>> 'library(.., include.only = *)' till now.
>
> I don't think it makes sense.  I would assume that
>
>  library(Matrix, include.only="isDiagonal")
>
> implies that only `isDiagonal` ends up on the search path, i.e. 
> "include.only" means "include only", not "include in addition to whatever 
> else has already been attached".
>
> I think a far better approach to solve Michael's problem is simply to use
>
>  fac2sparse <- Matrix::fac2sparse
>  isDiagonal <- Matrix::isDiagonal
>
> instead of messing around with the user's search list, which may have been 
> intentionally set to include only one of those.
>
> So I'd suggest changing the docs to say
>
> "[library and require] check and update the list of currently attached
> packages and do not reload a namespace which is already loaded.  If a package 
> is already attached, no change will be made."

?library could also mention using detach() followed by library() or
attachNamespace() with a new include.only specification.

Best,

luke

>
> Duncan Murdoch
>
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>

-- 
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:   luke-tierney using uiowa.edu
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