Support nullable external_ptr<> (implement #312)

cpp11test/R/cpp11.R

@@ -236,6 +236,14 @@ rcpp_push_and_truncate_ <- function(size_sxp) {
   .Call(`_cpp11test_rcpp_push_and_truncate_`, size_sxp)
 }
 
+nullable_extptr_1 <- function() {
+  .Call(`_cpp11test_nullable_extptr_1`)
+}
+
+nullable_extptr_2 <- function() {
+  .Call(`_cpp11test_nullable_extptr_2`)
+}
+
 test_destruction_inner <- function() {
   invisible(.Call(`_cpp11test_test_destruction_inner`))
 }

cpp11test/src/cpp11.cpp

@@ -443,6 +443,20 @@ extern "C" SEXP _cpp11test_rcpp_push_and_truncate_(SEXP size_sxp) {
     return cpp11::as_sexp(rcpp_push_and_truncate_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(size_sxp)));
   END_CPP11
 }
+// test-external_pointer.cpp
+cpp11::external_pointer<int> nullable_extptr_1();
+extern "C" SEXP _cpp11test_nullable_extptr_1() {
+  BEGIN_CPP11
+    return cpp11::as_sexp(nullable_extptr_1());
+  END_CPP11
+}
+// test-external_pointer.cpp
+cpp11::external_pointer<int> nullable_extptr_2();
+extern "C" SEXP _cpp11test_nullable_extptr_2() {
+  BEGIN_CPP11
+    return cpp11::as_sexp(nullable_extptr_2());
+  END_CPP11
+}
 // test-protect-nested.cpp
 void test_destruction_inner();
 extern "C" SEXP _cpp11test_test_destruction_inner() {
@@ -500,6 +514,8 @@ static const R_CallMethodDef CallEntries[] = {
     {"_cpp11test_my_warning_n1",            (DL_FUNC) &_cpp11test_my_warning_n1,            1},
     {"_cpp11test_my_warning_n1fmt",         (DL_FUNC) &_cpp11test_my_warning_n1fmt,         1},
     {"_cpp11test_my_warning_n2fmt",         (DL_FUNC) &_cpp11test_my_warning_n2fmt,         2},
+    {"_cpp11test_nullable_extptr_1",        (DL_FUNC) &_cpp11test_nullable_extptr_1,        0},
+    {"_cpp11test_nullable_extptr_2",        (DL_FUNC) &_cpp11test_nullable_extptr_2,        0},
     {"_cpp11test_protect_many_",            (DL_FUNC) &_cpp11test_protect_many_,            1},
     {"_cpp11test_protect_many_cpp11_",      (DL_FUNC) &_cpp11test_protect_many_cpp11_,      1},
     {"_cpp11test_protect_many_preserve_",   (DL_FUNC) &_cpp11test_protect_many_preserve_,   1},

cpp11test/src/test-external_pointer.cpp

@@ -10,6 +10,15 @@ void deleter(int* ptr) {
   delete ptr;
 }
 
+// Pacha: Test nullable external_pointer (#312)
+[[cpp11::register]] cpp11::external_pointer<int> nullable_extptr_1() {
+  return cpp11::external_pointer<int>(nullptr);
+}
+
+[[cpp11::register]] cpp11::external_pointer<int> nullable_extptr_2() {
+  return cpp11::external_pointer<int>(R_NilValue);
+}
+
 context("external_pointer-C++") {
   test_that("external_pointer works") {
     std::vector<int>* v = new std::vector<int>;

cpp11test/tests/testthat/test-external-pointer.R

@@ -0,0 +1,11 @@
+# Pacha: test that nullable external pointer is consistent (#312)
+test_that("nullable external pointer is consistent", {
+
+  len <- 1e5
+  set.seed(42)
+  x <- rnorm(len)
+  sum_base <- sum(x)
+
+  expect_equal(nullable_extptr_1(), NULL)
+  expect_equal(nullable_extptr_2(), NULL)
+})

inst/include/cpp11/external_pointer.hpp

@@ -23,8 +23,9 @@ class external_pointer {
   sexp data_ = R_NilValue;
 
   static SEXP valid_type(SEXP data) {
-    if (data == nullptr) {
-      throw type_error(EXTPTRSXP, NILSXP);
+    // Pacha: Allow nullable external_pointer (#312)
+    if (data == R_NilValue) {
+      return data;
     }
     if (detail::r_typeof(data) != EXTPTRSXP) {
       throw type_error(EXTPTRSXP, detail::r_typeof(data));
@@ -120,7 +121,8 @@ class external_pointer {
     data_ = tmp;
   }
 
-  operator bool() noexcept { return data_ != nullptr; }
+  // Pacha: Support nullable external_pointer (#312)
+  operator bool() const noexcept { return data_ != R_NilValue; }
 };
 
 template <class T, void Deleter(T*)>