Use rvalue subcasting when casting an rvalue container
This updates the std::tuple, std::pair and `stl.h` type casters to
forward their contained value according to whether the container being
cast is an lvalue or rvalue reference. This fixes an issue where
subcaster casts were always called with a const lvalue which meant
nested type casters didn't have the desired `cast()` overload invoked.
For example, this caused Eigen values in a tuple to end up with a
readonly flag (issue #935) and made it impossible to return a container
of move-only types (issue #853).
This fixes both issues by adding templated universal reference `cast()`
methods to the various container types that forward container elements
according to the container reference type.
diff --git a/tests/test_stl.py b/tests/test_stl.py
index fdbca0d..0f01982 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -58,6 +58,25 @@
assert doc(m.load_set) == "load_set(arg0: Set[str]) -> bool"
+def test_recursive_casting():
+ """Tests that stl casters preserve lvalue/rvalue context for container values"""
+ assert m.cast_rv_vector() == ["rvalue", "rvalue"]
+ assert m.cast_lv_vector() == ["lvalue", "lvalue"]
+ assert m.cast_rv_array() == ["rvalue", "rvalue", "rvalue"]
+ assert m.cast_lv_array() == ["lvalue", "lvalue"]
+ assert m.cast_rv_map() == {"a": "rvalue"}
+ assert m.cast_lv_map() == {"a": "lvalue", "b": "lvalue"}
+ assert m.cast_rv_nested() == [[[{"b": "rvalue", "c": "rvalue"}], [{"a": "rvalue"}]]]
+ assert m.cast_lv_nested() == {
+ "a": [[["lvalue", "lvalue"]], [["lvalue", "lvalue"]]],
+ "b": [[["lvalue", "lvalue"], ["lvalue", "lvalue"]]]
+ }
+
+ # Issue #853 test case:
+ z = m.cast_unique_ptr_vector()
+ assert z[0].value == 7 and z[1].value == 42
+
+
def test_move_out_container():
"""Properties use the `reference_internal` policy by default. If the underlying function
returns an rvalue, the policy is automatically changed to `move` to avoid referencing