py_to_r does not unwrap external pointer

[llaniewski]

Currently the py_to_r function does not unwrap an external pointer from a capsule. Namely py_to_r(r_to_py(x)) is not x if x is a R external pointer.

Code to reproduce:

library(reticulate)
library(Rcpp)

cppFunction("
SEXP fun() {
  static int k = 17;
  Rcpp::XPtr< int > ret(&k);
  return ret;
} 
")

x = fun()

identical( py_to_r(r_to_py(x)), x )

I'm open to writing a pull request with the correct the behaviour of py_to_r() function in src/python.cpp.

[t-kalinowski]

Hello, thanks for reporting! I agree this should work. A PR would be most welcome!

(If I recall correctly, this does touch a somewhat gnarly part of the codebase, not a fix I'd expect from a first-time contributor :).

We'll certainly want to fix before the next release.

[llaniewski]

@t-kalinowski I solved the immediate problem in my code using reticulate:::py_capsule and did not have time to address this more general issue in reticulate itself. But now I had finally a minute and made the necessary changes in a PR (#1519). Please write if you would want me to add some tests to that.