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Add type_caster<std::monostate> (#3818)

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* Add type_caster<std::monostate> for std::variant

Add type_caster<std::monostate>, allowing std::variant<std::monostate, ...>

* Add  variant<std::monostate, ...> test methods

* Add std::monostate tests

* Update test_stl.py

Remove erroneous extra tests

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update test fn name

* And update the doc() test

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
This commit is contained in:
Laramie Leavitt 2022-03-21 22:58:04 -07:00 committed by GitHub
parent 67089cd3e6
commit b22ee64c73
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3 changed files with 37 additions and 2 deletions
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3
include/pybind11/stl.h
View File

@ -406,6 +406,9 @@ struct variant_caster<V<Ts...>> {
#if defined(PYBIND11_HAS_VARIANT)
template <typename... Ts>
struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> {};
template <>
struct type_caster<std::monostate> : public void_caster<std::monostate> {};
#endif
PYBIND11_NAMESPACE_END(detail)

20
tests/test_stl.cpp
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@ -37,9 +37,10 @@ struct type_caster<boost::none_t> : void_caster<boost::none_t> {};
// Test with `std::variant` in C++17 mode, or with `boost::variant` in C++11/14
#if defined(PYBIND11_HAS_VARIANT)
using std::variant;
# define PYBIND11_TEST_VARIANT 1
#elif defined(PYBIND11_TEST_BOOST)
# include <boost/variant.hpp>
# define PYBIND11_HAS_VARIANT 1
# define PYBIND11_TEST_VARIANT 1
using boost::variant;
namespace pybind11 {
@ -424,7 +425,7 @@ TEST_SUBMODULE(stl, m) {
m.def("parent_path", [](const std::filesystem::path &p) { return p.parent_path(); });
#endif
#ifdef PYBIND11_HAS_VARIANT
#ifdef PYBIND11_TEST_VARIANT
static_assert(std::is_same<py::detail::variant_caster_visitor::result_type, py::handle>::value,
"visitor::result_type is required by boost::variant in C++11 mode");
@ -435,6 +436,9 @@ TEST_SUBMODULE(stl, m) {
result_type operator()(const std::string &) { return "std::string"; }
result_type operator()(double) { return "double"; }
result_type operator()(std::nullptr_t) { return "std::nullptr_t"; }
# if defined(PYBIND11_HAS_VARIANT)
result_type operator()(std::monostate) { return "std::monostate"; }
# endif
};
// test_variant
@ -448,6 +452,18 @@ TEST_SUBMODULE(stl, m) {
using V = variant<int, std::string>;
return py::make_tuple(V(5), V("Hello"));
});
# if defined(PYBIND11_HAS_VARIANT)
// std::monostate tests.
m.def("load_monostate_variant",
[](const variant<std::monostate, int, std::string> &v) -> const char * {
return py::detail::visit_helper<variant>::call(visitor(), v);
});
m.def("cast_monostate_variant", []() {
using V = variant<std::monostate, int, std::string>;
return py::make_tuple(V{}, V(5), V("Hello"));
});
# endif
#endif
// #528: templated constructor

16
tests/test_stl.py
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@ -263,6 +263,22 @@ def test_variant(doc):
)
@pytest.mark.skipif(
not hasattr(m, "load_monostate_variant"), reason="no std::monostate"
)
def test_variant_monostate(doc):
assert m.load_monostate_variant(None) == "std::monostate"
assert m.load_monostate_variant(1) == "int"
assert m.load_monostate_variant("1") == "std::string"
assert m.cast_monostate_variant() == (None, 5, "Hello")
assert (
doc(m.load_monostate_variant)
== "load_monostate_variant(arg0: Union[None, int, str]) -> str"
)
def test_vec_of_reference_wrapper():
"""#171: Can't return reference wrappers (or STL structures containing them)"""
assert (