named argument confusion in Rcpp-modules - r

Question

I want to create a package in R that uses cpp-code with the Rcpp package. In the cpp-code I need to use classes and member functions with named arguments.
After building the package, functions inside of Rcpp-modules seem to be ignoring named inputs and parse by position instead.
For example using the test package, as described below, I get the following output
# test the library
library(test)
# foo1 is a function outside of a module
foo1(a = "a", b = "b") # works as expected
#> a is a, b is b
foo1(b = "b", a = "a") # works as expected
#> a is a, b is b
# function within module "ABCMODULE"
foo2(a = "a", b = "b") # works as expected
#> a is a; b is b
foo2(b = "b", a = "a") # switches arguments <-------
#> a is b; b is a
abc <- new(ABC)
abc$foo3(a = "a", b = "b") # works as expected
#> a is a; b is b
abc$foo3(b = "b", a = "a") # switches arguments <-------
#> a is b; b is a
I have looked into the many Rcpp-vignettes but could find any solution to this. Have I overlooked something in the documents? Did I do a mistake somewhere? And how can I solve this or is this a feature/bug?
Edit
On a similar note, when I try to set default values, i.e., std::string b = "b" in all code (updated below), the Rcpp-module-versions do not work when trying to use the default value (foo1(a = "a") results in Error Expecting single string value and abc$foo3(a = "a") results in Error in ... could not find valid method)
test package
I have created the package with
Rcpp::Rcpp.package.skeleton("test", module = T)
then I added the two following files in test/
added src/foo1.cpp
#include <Rcpp.h>
using namespace Rcpp;
// [[Rcpp::export]]
void foo1(std::string a, std::string b = "b") {
Rprintf("a is %s, b is %s", a.c_str(), b.c_str());
}
added src/ABC.cpp
// -*- mode: C++; c-indent-level: 4; c-basic-offset: 4; indent-tabs-mode: nil; -*-
#include <Rcpp.h>
void foo2(std::string a, std::string b = "b") {
Rprintf("a is %s; b is %s\n", a.c_str(), b.c_str());
}
class ABC {
public:
ABC() {}
void foo3(std::string a, std::string b = "b");
};
void ABC::foo3(std::string a, std::string b) {
Rprintf("a is %s; b is %s\n", a.c_str(), b.c_str());
}
RCPP_MODULE(ABCMODULE){
using namespace Rcpp ;
function("foo2" , &foo2 , "documentation for foo2");
// with formal arguments specification
class_<ABC>("ABC")
// expose the default constructor
.constructor()
.method("foo3", &ABC::foo3 , "documentation for foo3")
;
}
modified R/zzz.R
I added the following line to the bottom of the file
loadModule("ABCMODULE", TRUE)