fixed regression in STL type caster RVPs (fixes #1561) (#1603)

.appveyor.yml

@@ -3,6 +3,7 @@ image:
 - Visual Studio 2017
 - Visual Studio 2015
 test: off
+skip_branch_with_pr: true
 build:
   parallel: true
 platform:

include/pybind11/cast.h

@@ -1614,7 +1614,8 @@ template <typename Return, typename SFINAE = void> struct return_value_policy_ov
 template <typename Return> struct return_value_policy_override<Return,
         detail::enable_if_t<std::is_base_of<type_caster_generic, make_caster<Return>>::value, void>> {
     static return_value_policy policy(return_value_policy p) {
-        return !std::is_lvalue_reference<Return>::value && !std::is_pointer<Return>::value
+        return !std::is_lvalue_reference<Return>::value &&
+               !std::is_pointer<Return>::value
                    ? return_value_policy::move : p;
     }
 };

include/pybind11/stl.h

@@ -83,6 +83,7 @@ template <typename Type, typename Key> struct set_caster {
 
     template <typename T>
     static handle cast(T &&src, return_value_policy policy, handle parent) {
+        if (!std::is_lvalue_reference<T>::value)
             policy = return_value_policy_override<Key>::policy(policy);
         pybind11::set s;
         for (auto &&value : src) {
@@ -119,8 +120,12 @@ template <typename Type, typename Key, typename Value> struct map_caster {
     template <typename T>
     static handle cast(T &&src, return_value_policy policy, handle parent) {
         dict d;
-        return_value_policy policy_key = return_value_policy_override<Key>::policy(policy);
-        return_value_policy policy_value = return_value_policy_override<Value>::policy(policy);
+        return_value_policy policy_key = policy;
+        return_value_policy policy_value = policy;
+        if (!std::is_lvalue_reference<T>::value) {
+            policy_key = return_value_policy_override<Key>::policy(policy_key);
+            policy_value = return_value_policy_override<Value>::policy(policy_value);
+        }
         for (auto &&kv : src) {
             auto key = reinterpret_steal<object>(key_conv::cast(forward_like<T>(kv.first), policy_key, parent));
             auto value = reinterpret_steal<object>(value_conv::cast(forward_like<T>(kv.second), policy_value, parent));
@@ -161,6 +166,7 @@ private:
 public:
     template <typename T>
     static handle cast(T &&src, return_value_policy policy, handle parent) {
+        if (!std::is_lvalue_reference<T>::value)
             policy = return_value_policy_override<Value>::policy(policy);
         list l(src.size());
         size_t index = 0;

tests/test_stl.cpp

@@ -265,4 +265,16 @@ TEST_SUBMODULE(stl, m) {
           py::return_value_policy::take_ownership);
 
     m.def("array_cast_sequence", [](std::array<int, 3> x) { return x; });
+
+    /// test_issue_1561
+    struct Issue1561Inner { std::string data; };
+    struct Issue1561Outer { std::vector<Issue1561Inner> list; };
+
+    py::class_<Issue1561Inner>(m, "Issue1561Inner")
+        .def(py::init<std::string>())
+        .def_readwrite("data", &Issue1561Inner::data);
+
+    py::class_<Issue1561Outer>(m, "Issue1561Outer")
+        .def(py::init<>())
+        .def_readwrite("list", &Issue1561Outer::list);
 }

tests/test_stl.py

@@ -220,3 +220,11 @@ def test_stl_ownership():
 
 def test_array_cast_sequence():
     assert m.array_cast_sequence((1, 2, 3)) == [1, 2, 3]
+
+
+def test_issue_1561():
+    """ check fix for issue #1561 """
+    bar = m.Issue1561Outer()
+    bar.list = [m.Issue1561Inner('bar')]
+    bar.list
+    assert bar.list[0].data == 'bar'