Fix push_back with named arguments

It should now work much more consistently than previously

Fixes #86

Author: jimhester

NEWS.md

@@ -1,5 +1,7 @@
 # cpp11 (development version)
 
+* `push_back()` now works more consistently with named arguments (#86)
+
 # cpp11 0.2.0
 
 ## New features

cpp11test/src/test-list.cpp

@@ -47,6 +47,64 @@ context("list-C++") {
     expect_true(fifth[2] == 'c');
   }
 
+  using namespace cpp11::literals;
+  test_that("unnamed_list.push_back(unnamed_arg)") {
+    cpp11::writable::list x(1);
+    x.push_back(cpp11::writable::integers(2));
+
+    expect_true(x.names() == R_NilValue);
+  }
+
+  test_that("unnamed_list.push_back(named_arg)") {
+    cpp11::writable::list x(1);
+    x.push_back("bar"_nm = 2);
+
+    cpp11::strings nms(x.names());
+
+    expect_true(nms.size() == 2);
+    expect_true(nms[0] == "");
+    expect_true(nms[1] == "bar");
+  }
+
+  test_that("named_list.push_back(unnamed_arg)") {
+    cpp11::writable::list x({"foo"_nm = 1});
+    x.push_back(cpp11::writable::integers(2));
+
+    cpp11::strings nms(x.names());
+
+    expect_true(nms.size() == 2);
+    expect_true(nms[0] == "foo");
+    expect_true(nms[1] == "");
+  }
+
+  test_that("named_list.push_back(named_arg)") {
+    cpp11::writable::list x({"foo"_nm = 1});
+    x.push_back({"bar"_nm = 2});
+
+    cpp11::strings nms(x.names());
+
+    expect_true(nms.size() == 2);
+    expect_true(nms[0] == "foo");
+    expect_true(nms[1] == "bar");
+  }
+
+  test_that("empty_list.push_back(unnamed_arg)") {
+    cpp11::writable::list x;
+    x.push_back(cpp11::writable::integers(2));
+
+    expect_true(x.names() == R_NilValue);
+  }
+
+  test_that("empty_list.push_back(named_arg)") {
+    cpp11::writable::list x;
+    x.push_back({"bar"_nm = 2});
+
+    cpp11::strings nms(x.names());
+
+    expect_true(nms.size() == 1);
+    expect_true(nms[0] == "bar");
+  }
+
   test_that("attribute setting works") {
     cpp11::writable::list x(
         {cpp11::writable::doubles({1, 2, 3}), cpp11::writable::strings({"x", "y", "z"})});

inst/include/cpp11/r_vector.hpp

@@ -330,6 +330,7 @@ class r_vector : public cpp11::r_vector<T> {
 
   using cpp11::r_vector<T>::cbegin;
   using cpp11::r_vector<T>::cend;
+  using cpp11::r_vector<T>::size;
 
   iterator find(const r_string& name) const;
 

inst/include/cpp11/strings.hpp

@@ -172,8 +172,12 @@ typedef r_vector<r_string> strings;
 template <typename T>
 inline void r_vector<T>::push_back(const named_arg& value) {
   push_back(value.value());
+  if (Rf_xlength(names()) == 0) {
+    cpp11::writable::strings new_nms(size());
+    names() = new_nms;
+  }
   cpp11::writable::strings nms(names());
-  nms.push_back(value.name());
+  nms[size() - 1] = value.name();
 }
 
 }  // namespace writable