[Rd] R_GetCurrentEnv() not working as intended

[Lionel Henry]

Hello,

This function currently does not work when called from `.Call()`.
This is reported with a patch at
https://bugs.r-project.org/show_bug.cgi?id=17839

In the meantime, you can use this stopgap implementation:

https://github.com/tidyverse/purrr/blob/55c9a8ab8788d878ce9e8e80b867139e46d15395/src/conditions.c#L6-L34

Best,
Lionel

On 11/13/22, Charlie Gao via R-devel <r-devel using r-project.org> wrote:
> Perhaps my original question was too complicated, so I will just ask: is
> anyone using R_GetCurrentEnv() in their C code? If so, grateful if you could
> point me to an example where it is working for you.
>
> I have searched Github and only come across a couple of trivial uses as an
> argument to Rf_eval(), where it probably returns the global environment,
> with the result being indistinguishable in normal use.
>
> Thanks,
>
> Charlie
>
> October 22, 2022 12:52 AM, "Charlie Gao" <charlie.gao using shikokuchuo.net>
> wrote:
>
>> Dear all,
>>
>> I am attempting to use `R_GetCurrentEnv()` to return the current
>> environment within C code, but it
>> seems to always return the global environment.
>>
>> Specifically, I would like to use it as an argument to R_NewEnv() so it is
>> created with the correct
>> enclosing environment. I also have functions in the environment that
>> reference symbols in the
>> closure and I would also like to use `R_GetCurrentEnv()` as an argument to
>> `SET_CLOENV()`.
>>
>> My workaround at the moment is to pass `environment()` as one of the
>> arguments to the `.Call()`.
>> For the actual code I am referring to:
>>
>> https://github.com/shikokuchuo/nanonext/blob/main/src/aio.c#L516-L535
>>
>> where I am currently passing `environment()` as 'clo' whereas ideally I
>> would be able to use
>> `R_GetCurrentEnv()` instead.
>>
>> There is an open Bugzilla report from 2020 that says `R_GetCurrentEnv()`
>> only returns the base
>> namespace from within a `.Call()`, however I see that the proposed patch
>> has already been adopted
>> in the R source.
>>
>> It seems that the function was introduced (fairly) recently in R 3.6,
>> presumably for such uses. I
>> would like to know if this is not the case or else confirmation that this
>> is an outstanding bug.
>>
>> Thanks,
>>
>> Charlie
>
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