env argument not used to actually source the R code #851
Description
If you set the env variable in sourceCpp, Rcpp correctly makes the R functions and modules available in the specified environment. However, the R snippet in the /*** R block is not executed in this same environment. This causes unexpected errors.
Reproducible example
test.rcpp
#include <Rcpp.h>
using namespace Rcpp ;
// [[Rcpp::export]]
int answer(){
return 42 ;
}
/*** R
# call answer and check you get the right result
x <- answer()
x
*/Next, in R:
library(Rcpp)
testEnv <- new.env()
sourceCpp("test.cpp", env = testEnv)
ls(testEnv)Expected output:
> library(Rcpp)
> testEnv <- new.env()
> sourceCpp("test.cpp", env = testEnv)
> # call answer and check you get the right result
> x <- answer()
> x
[1] 42
> ls(testEnv)
[1] "answer" "x"
Actual output:
> library(Rcpp)
> testEnv <- new.env()
> sourceCpp("test.cpp", env = testEnv)
> # call answer and check you get the right result
> x <- answer()
Error in answer() : could not find function "answer"
> ls(testEnv)
[1] "answer"
Context
I work at DataCamp, where we're building a course on Rcpp together with Romain Francois. Our R execution backend heavily relies on the concept of environments: we run the solution code in a solution environment and the student code in a student environment, so that we can check the equality of objects. Because of the above, it is currently very hard for Rcpp exercise to do this. For even more context, you can check out this issue.
Potential solution
I think that passing local = env to the source() call here fixes this, as done here. Before doing a PR, I wanted to know whether the current behavior is intended and what the authors' take on it is.
cc @sumedh10