test_pytypes: Show failing auto conversion?

Author: EricCousineau-TRI

tests/test_pytypes.cpp

@@ -319,6 +319,13 @@ TEST_SUBMODULE(pytypes, m) {
         return a[py::slice(0, -1, 2)];
     });
 
+    m.def("test_str_with_cpp_default_none", []() {
+        auto my_func = [](py::str value = py::none()) {
+            return value;
+        };
+        return py::make_tuple(my_func(), my_func("Hello"));
+    });
+
     m.def("test_memoryview_object", [](py::buffer b) {
         return py::memoryview(b);
     });

tests/test_pytypes.py

@@ -281,6 +281,10 @@ def test_list_slicing():
     assert li[::2] == m.test_list_slicing(li)
 
 
+def test_str_with_cpp_default_none():
+    assert m.test_str_with_cpp_default_none() == (None, "Hello")
+
+
 @pytest.mark.parametrize('method, args, fmt, expected_view', [
     (m.test_memoryview_object, (b'red',), 'B', b'red'),
     (m.test_memoryview_buffer_info, (b'green',), 'B', b'green'),