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

[Michael Chirico]

> I would assume that
>   library(Matrix, include.only="isDiagonal")
> implies that only `isDiagonal` ends up on the search path

This could also be a reasonable behavior, but neither does that happen
today.
> I think a far better approach to solve Michael's problem is simply to use
>   fac2sparse <- Matrix::fac2sparse

This does not fully simulate attachment, e.g. running package hooks &
resolving Depends.

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

This is the "quite hard to accomplish" I alluded to, admittedly I hadn't
forced myself to write it all out -- maybe it's not as bad as all that.
After some iterations, today I think we'd want to do...

modify_attach = function(pkg, new_names) {
  if (!startsWith(pkg, "package:")) pkg <- paste0("package:", pkg)
  old <- tryCatch(ls(pkg, all.names=TRUE), error=\(c) character())
  if (length(old)) detach(pkg)
  attachNamespace(.rmpkg(pkg), include.only=c(new_names, old))
}

Perhaps detach() could invisibly return the exported names to make this a
tiny bit easier (today it returns NULL):

modify_attach = function(pkg, new_names) {
  if (!startsWith(pkg, "package:")) pkg <- paste0("package:", pkg)
  old <- tryCatch(detach(pkg), error=\(c) character())
  attachNamespace(.rmpkg(pkg), include.only=c(new_names, old))
}

Regardless, I think your suggestion to just point to
detach()+attachNamespace() is reasonable enough, the rare users that care
about this are likely to be able to figure out the rest from there.

On Thu, Apr 11, 2024 at 7:37 AM <luke-tierney using uiowa.edu> wrote:

> 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
> >
> > ______________________________________________
> > R-devel using r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
>
> --
> 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
> Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu/

	[[alternative HTML version deleted]]