support for boost;:optional

src/boost.h

@@ -0,0 +1,39 @@
+#include <boost/optional.hpp>
+
+namespace pybind11 {
+    namespace detail {
+template<typename T> struct boost_optional_caster {
+    using value_conv = make_caster<typename T::value_type>;
+
+    static handle cast(const T& src, return_value_policy policy, handle parent) {
+        if (!src)
+            return none().inc_ref();
+        return value_conv::cast(*src, policy, parent);
+    }
+
+    bool load(handle src, bool convert) {
+        if (!src) {
+            return false;
+        } else if (src.is_none()) {
+            value = boost::none;  // nullopt
+            return true;
+        }
+        value_conv inner_caster;
+        if (!inner_caster.load(src, convert))
+            return false;
+
+        value.emplace(cast_op<typename T::value_type>(inner_caster));
+        return true;
+    }
+
+    PYBIND11_TYPE_CASTER(T, _("Optional[") + value_conv::name() + _("]"));
+};
+
+template<typename T> struct type_caster<boost::optional<T>>
+    : public boost_optional_caster<boost::optional<T>> {};
+
+template<> struct type_caster<boost::none_t>
+    : public void_caster<boost::none_t> {};
+
+    }
+}

src/common.h

@@ -20,3 +20,5 @@ using namespace pybind11::literals;
 
 PYBIND11_DECLARE_HOLDER_TYPE(T, std::shared_ptr<T>)
 PYBIND11_DECLARE_HOLDER_TYPE(T, std::shared_ptr<T const>)
+
+#include "boost.h"