[External] exists, get and get0 accept silently inputs of length > 1

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

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Luke Tierney
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