From 819cb5533ed8e1654a11e2defc6cd1ea8254ab86 Mon Sep 17 00:00:00 2001
From: Dean Moldovan <dean0x7d@gmail.com>
Date: Wed, 15 Mar 2017 13:57:10 +0100
Subject: [PATCH] Fix nullptr to None conversion for builtin type casters

Fixes #731.

Generally, this applies to any caster made with PYBIND11_TYPE_CASTER().
---
 include/pybind11/cast.h     |  1 +
 tests/test_python_types.cpp |  6 ++++++
 tests/test_python_types.py  | 11 +++++++++++
 3 files changed, 18 insertions(+)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index b8638b9c2..94d3e03b5 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -469,6 +469,7 @@ public:
     public: \
         static PYBIND11_DESCR name() { return type_descr(py_name); } \
         static handle cast(const type *src, return_value_policy policy, handle parent) { \
+            if (!src) return none().release(); \
             return cast(*src, policy, parent); \
         } \
         operator type*() { return &value; } \
diff --git a/tests/test_python_types.cpp b/tests/test_python_types.cpp
index 6a0044ca3..399129fad 100644
--- a/tests/test_python_types.cpp
+++ b/tests/test_python_types.cpp
@@ -464,6 +464,12 @@ test_initializer python_types([](py::module &m) {
     m.def("ord_char16", [](char16_t c) -> uint16_t { return c; });
     m.def("ord_char32", [](char32_t c) -> uint32_t { return c; });
     m.def("ord_wchar", [](wchar_t c) -> int { return c; });
+
+    m.def("return_none_string", []() -> std::string * { return nullptr; });
+    m.def("return_none_char",   []() -> const char *  { return nullptr; });
+    m.def("return_none_bool",   []() -> bool *        { return nullptr; });
+    m.def("return_none_int",    []() -> int *         { return nullptr; });
+    m.def("return_none_float",  []() -> float *       { return nullptr; });
 });
 
 #if defined(_MSC_VER)
diff --git a/tests/test_python_types.py b/tests/test_python_types.py
index cf5412dfa..7ca020e89 100644
--- a/tests/test_python_types.py
+++ b/tests/test_python_types.py
@@ -501,3 +501,14 @@ def test_single_char_arguments():
     with pytest.raises(ValueError) as excinfo:
         assert ord_wchar(u'aa')
     assert str(excinfo.value) == toolong_message
+
+
+def test_builtins_cast_return_none():
+    """Casters produced with PYBIND11_TYPE_CASTER() should convert nullptr to None"""
+    import pybind11_tests as m
+
+    assert m.return_none_string() is None
+    assert m.return_none_char() is None
+    assert m.return_none_bool() is None
+    assert m.return_none_int() is None
+    assert m.return_none_float() is None