R devel - Nov 2020 - [External] exists, get and get0 accept silently inputs of length > 1

Dear R-devel,

The doc of exists, get and get0 is unambiguous, x should be an object given
as a character string. However these accept longer inputs. It can lead an
uncareful user to think these functions are vectorized when they're not,
and generally lets through bugs that one might have preferred to trigger
earlier failure.

``` r
exists("d")
#> [1] FALSE
exists(c("c", "d"))
#> [1] TRUE
get(c("c", "d"))
#> function (...)  .Primitive("c")
get0(c("c", "d"))
#> function (...)  .Primitive("c")
```

I believe these should either fail, or be vectorized, probably the former.

Thanks,

Antoine

	[[alternative HTML version deleted]]

Worth looking into. It would probably cause some check failures, so
would probably be a good idea to run a check across BIOC/CRAN.  At the
same time it would be worth allowing name objects (type "symbol") so
thee don't have to be converted to character for the call and then
back to names internally for the environment lookup.

Best,

luke

On Fri, 13 Nov 2020, Antoine Fabri wrote:
> Dear R-devel,
>
> The doc of exists, get and get0 is unambiguous, x should be an object given
> as a character string. However these accept longer inputs. It can lead an
> uncareful user to think these functions are vectorized when they're
not,
> and generally lets through bugs that one might have preferred to trigger
> earlier failure.
>
> ``` r
> exists("d")
> #> [1] FALSE
> exists(c("c", "d"))
> #> [1] TRUE
> get(c("c", "d"))
> #> function (...)  .Primitive("c")
> get0(c("c", "d"))
> #> function (...)  .Primitive("c")
> ```
>
> I believe these should either fail, or be vectorized, probably the former.
>
> Thanks,
>
> Antoine
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-devel at 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 at uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu

I noticed the recent commit to R-dev (r79434).  Is this wise? I've
often used get() in constructions like

for (j in ls()) if (is.numeric(x <- get(j))) ...

(and often interactively, rather than in a package)

Am I to understand that get(j) will now be equivalent to `j` even if j
is a string referring putatively to another object?

On Sat, 14 Nov 2020 at 01:34, <luke-tierney at uiowa.edu>
wrote:
>
> Worth looking into. It would probably cause some check failures, so
> would probably be a good idea to run a check across BIOC/CRAN.  At the
> same time it would be worth allowing name objects (type "symbol")
so
> thee don't have to be converted to character for the call and then
> back to names internally for the environment lookup.
>
> Best,
>
> luke
>
> On Fri, 13 Nov 2020, Antoine Fabri wrote:
>
> > Dear R-devel,
> >
> > The doc of exists, get and get0 is unambiguous, x should be an object
given
> > as a character string. However these accept longer inputs. It can lead
an
> > uncareful user to think these functions are vectorized when
they're not,
> > and generally lets through bugs that one might have preferred to
trigger
> > earlier failure.
> >
> > ``` r
> > exists("d")
> > #> [1] FALSE
> > exists(c("c", "d"))
> > #> [1] TRUE
> > get(c("c", "d"))
> > #> function (...)  .Primitive("c")
> > get0(c("c", "d"))
> > #> function (...)  .Primitive("c")
> > ```
> >
> > I believe these should either fail, or be vectorized, probably the
former.
> >
> > Thanks,
> >
> > Antoine
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-devel at 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 at uiowa.edu
> Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

Thanks for the suggestion.

In R-devel (as of r79474) exists(), get(), and get0() now signal an
error if the first argument has length > 1. This will cause about 30
CRAN packages and possibly a couple of Bioconductor packages to fail
under R-devel.

getS3method() now also signals an error if the class argument has
length > 1. Calls of the form getS2method(generic, class(x)) will now
fail if class(x) has length > 1. I believe most CRAN package issues
related to this change have already been resolved, but a few may
remain.

Best,

luke

On Fri, 13 Nov 2020, Antoine Fabri wrote:
> Dear R-devel,
>
> The doc of exists, get and get0 is unambiguous, x should be an object given
> as a character string. However these accept longer inputs. It can lead an
> uncareful user to think these functions are vectorized when they're
not,
> and generally lets through bugs that one might have preferred to trigger
> earlier failure.
>
> ``` r
> exists("d")
> #> [1] FALSE
> exists(c("c", "d"))
> #> [1] TRUE
> get(c("c", "d"))
> #> function (...)  .Primitive("c")
> get0(c("c", "d"))
> #> function (...)  .Primitive("c")
> ```
>
> I believe these should either fail, or be vectorized, probably the former.
>
> Thanks,
>
> Antoine
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-devel at 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 at uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu