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fix: the types for return_value_policy_override in optional_caster (#3376)
* fix: the types for return_value_policy_override in optional_caster `return_value_policy_override` was not being applied correctly in `optional_caster` in two ways: - The `is_lvalue_reference` condition referenced `T`, which was the `optional<T>` type parameter from the class, when it should have used `T_`, which was the parameter to the `cast` function. `T_` can potentially be a reference type, but `T` will never be. - The type parameter passed to `return_value_policy_override` should be `T::value_type`, not `T`. This matches the way that the other STL container type casters work. The result of these issues was that a method/property definition which used a `reference` or `reference_internal` return value policy would create a Python value that's bound by reference to a temporary C++ object, resulting in undefined behavior. For reasons that I was not able to figure out fully, it seems like this causes problems when using old versions of `boost::optional`, but not with recent versions of `boost::optional` or the `libstdc++` implementation of `std::optional`. The issue (that the override to `return_value_policy::move` is never being applied) is present for all implementations, it just seems like that somehow doesn't result in problems for the some implementation of `optional`. This change includes a regression type with a custom optional-like type which was able to reproduce the issue. Part of the issue with using the wrong types may have stemmed from the type variables `T` and `T_` having very similar names. This also changes the type variables in `optional_caster` to use slightly more descriptive names, which also more closely follow the naming convention used by the other STL casters. Fixes #3330 * Fix clang-tidy complaints * Add missing NOLINT * Apply a couple more fixes * fix: support GCC 4.8 * tests: avoid warning about unknown compiler for compilers missing C++17 * Remove unneeded test module attribute * Change test enum to have more unique int values Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com> Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
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@ -245,17 +245,17 @@ template <typename Key, typename Value, typename Hash, typename Equal, typename
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: map_caster<std::unordered_map<Key, Value, Hash, Equal, Alloc>, Key, Value> { };
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// This type caster is intended to be used for std::optional and std::experimental::optional
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template<typename T> struct optional_caster {
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using value_conv = make_caster<typename T::value_type>;
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template<typename Type, typename Value = typename Type::value_type> struct optional_caster {
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using value_conv = make_caster<Value>;
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template <typename T_>
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static handle cast(T_ &&src, return_value_policy policy, handle parent) {
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template <typename T>
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static handle cast(T &&src, return_value_policy policy, handle parent) {
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if (!src)
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return none().inc_ref();
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if (!std::is_lvalue_reference<T>::value) {
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policy = return_value_policy_override<T>::policy(policy);
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policy = return_value_policy_override<Value>::policy(policy);
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}
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return value_conv::cast(*std::forward<T_>(src), policy, parent);
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return value_conv::cast(*std::forward<T>(src), policy, parent);
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}
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bool load(handle src, bool convert) {
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@ -269,11 +269,11 @@ template<typename T> struct optional_caster {
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if (!inner_caster.load(src, convert))
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return false;
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value.emplace(cast_op<typename T::value_type &&>(std::move(inner_caster)));
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value.emplace(cast_op<Value &&>(std::move(inner_caster)));
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return true;
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}
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PYBIND11_TYPE_CASTER(T, _("Optional[") + value_conv::name + _("]"));
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PYBIND11_TYPE_CASTER(Type, _("Optional[") + value_conv::name + _("]"));
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};
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#if defined(PYBIND11_HAS_OPTIONAL)
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@ -256,7 +256,9 @@ if(Boost_FOUND)
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endif()
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# Check if we need to add -lstdc++fs or -lc++fs or nothing
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if(MSVC)
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if(DEFINED CMAKE_CXX_STANDARD AND CMAKE_CXX_STANDARD LESS 17)
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set(STD_FS_NO_LIB_NEEDED TRUE)
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elseif(MSVC)
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set(STD_FS_NO_LIB_NEEDED TRUE)
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else()
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file(
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@ -286,7 +288,7 @@ elseif(${STD_FS_NEEDS_CXXFS})
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elseif(${STD_FS_NO_LIB_NEEDED})
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set(STD_FS_LIB "")
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else()
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message(WARNING "Unknown compiler - not passing -lstdc++fs")
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message(WARNING "Unknown C++17 compiler - not passing -lstdc++fs")
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set(STD_FS_LIB "")
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endif()
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@ -19,6 +19,18 @@
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#include <vector>
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#include <string>
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#if defined(PYBIND11_TEST_BOOST)
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#include <boost/optional.hpp>
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namespace pybind11 { namespace detail {
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template <typename T>
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struct type_caster<boost::optional<T>> : optional_caster<boost::optional<T>> {};
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template <>
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struct type_caster<boost::none_t> : void_caster<boost::none_t> {};
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}} // namespace pybind11::detail
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#endif
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// Test with `std::variant` in C++17 mode, or with `boost::variant` in C++11/14
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#if defined(PYBIND11_HAS_VARIANT)
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using std::variant;
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@ -59,7 +71,8 @@ namespace std {
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template <template <typename> class OptionalImpl, typename T>
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struct OptionalHolder
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{
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OptionalHolder() = default;
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// NOLINTNEXTLINE(modernize-use-equals-default): breaks GCC 4.8
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OptionalHolder() {};
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bool member_initialized() const {
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return member && member->initialized;
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}
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@ -67,6 +80,95 @@ struct OptionalHolder
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};
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enum class EnumType {
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kSet = 42,
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kUnset = 85,
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};
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// This is used to test that return-by-ref and return-by-copy policies are
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// handled properly for optional types. This is a regression test for a dangling
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// reference issue. The issue seemed to require the enum value type to
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// reproduce - it didn't seem to happen if the value type is just an integer.
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template <template <typename> class OptionalImpl>
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class OptionalProperties {
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public:
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using OptionalEnumValue = OptionalImpl<EnumType>;
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OptionalProperties() : value(EnumType::kSet) {}
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~OptionalProperties() {
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// Reset value to detect use-after-destruction.
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// This is set to a specific value rather than nullopt to ensure that
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// the memory that contains the value gets re-written.
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value = EnumType::kUnset;
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}
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OptionalEnumValue& access_by_ref() { return value; }
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OptionalEnumValue access_by_copy() { return value; }
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private:
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OptionalEnumValue value;
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};
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// This type mimics aspects of boost::optional from old versions of Boost,
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// which exposed a dangling reference bug in Pybind11. Recent versions of
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// boost::optional, as well as libstdc++'s std::optional, don't seem to be
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// affected by the same issue. This is meant to be a minimal implementation
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// required to reproduce the issue, not fully standard-compliant.
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// See issue #3330 for more details.
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template <typename T>
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class ReferenceSensitiveOptional {
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public:
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using value_type = T;
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ReferenceSensitiveOptional() = default;
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// NOLINTNEXTLINE(google-explicit-constructor)
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ReferenceSensitiveOptional(const T& value) : storage{value} {}
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// NOLINTNEXTLINE(google-explicit-constructor)
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ReferenceSensitiveOptional(T&& value) : storage{std::move(value)} {}
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ReferenceSensitiveOptional& operator=(const T& value) {
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storage = {value};
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return *this;
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}
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ReferenceSensitiveOptional& operator=(T&& value) {
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storage = {std::move(value)};
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return *this;
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}
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template <typename... Args>
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T& emplace(Args&&... args) {
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storage.clear();
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storage.emplace_back(std::forward<Args>(args)...);
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return storage.back();
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}
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const T& value() const noexcept {
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assert(!storage.empty());
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return storage[0];
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}
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const T& operator*() const noexcept {
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return value();
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}
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const T* operator->() const noexcept {
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return &value();
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}
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explicit operator bool() const noexcept {
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return !storage.empty();
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}
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private:
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std::vector<T> storage;
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};
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namespace pybind11 { namespace detail {
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template <typename T>
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struct type_caster<ReferenceSensitiveOptional<T>> : optional_caster<ReferenceSensitiveOptional<T>> {};
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} // namespace detail
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} // namespace pybind11
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TEST_SUBMODULE(stl, m) {
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// test_vector
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m.def("cast_vector", []() { return std::vector<int>{1}; });
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@ -145,6 +247,10 @@ TEST_SUBMODULE(stl, m) {
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return v;
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});
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pybind11::enum_<EnumType>(m, "EnumType")
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.value("kSet", EnumType::kSet)
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.value("kUnset", EnumType::kUnset);
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// test_move_out_container
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struct MoveOutContainer {
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struct Value { int value; };
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@ -213,6 +319,12 @@ TEST_SUBMODULE(stl, m) {
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.def(py::init<>())
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.def_readonly("member", &opt_holder::member)
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.def("member_initialized", &opt_holder::member_initialized);
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using opt_props = OptionalProperties<std::optional>;
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pybind11::class_<opt_props>(m, "OptionalProperties")
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.def(pybind11::init<>())
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.def_property_readonly("access_by_ref", &opt_props::access_by_ref)
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.def_property_readonly("access_by_copy", &opt_props::access_by_copy);
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#endif
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#ifdef PYBIND11_HAS_EXP_OPTIONAL
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@ -239,8 +351,75 @@ TEST_SUBMODULE(stl, m) {
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.def(py::init<>())
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.def_readonly("member", &opt_exp_holder::member)
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.def("member_initialized", &opt_exp_holder::member_initialized);
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using opt_exp_props = OptionalProperties<std::experimental::optional>;
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pybind11::class_<opt_exp_props>(m, "OptionalExpProperties")
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.def(pybind11::init<>())
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.def_property_readonly("access_by_ref", &opt_exp_props::access_by_ref)
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.def_property_readonly("access_by_copy", &opt_exp_props::access_by_copy);
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#endif
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#if defined(PYBIND11_TEST_BOOST)
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// test_boost_optional
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m.attr("has_boost_optional") = true;
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using boost_opt_int = boost::optional<int>;
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using boost_opt_no_assign = boost::optional<NoAssign>;
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m.def("double_or_zero_boost", [](const boost_opt_int& x) -> int {
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return x.value_or(0) * 2;
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});
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m.def("half_or_none_boost", [](int x) -> boost_opt_int {
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return x != 0 ? boost_opt_int(x / 2) : boost_opt_int();
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});
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m.def("test_nullopt_boost", [](boost_opt_int x) {
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return x.value_or(42);
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}, py::arg_v("x", boost::none, "None"));
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m.def("test_no_assign_boost", [](const boost_opt_no_assign &x) {
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return x ? x->value : 42;
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}, py::arg_v("x", boost::none, "None"));
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using opt_boost_holder = OptionalHolder<boost::optional, MoveOutDetector>;
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py::class_<opt_boost_holder>(m, "OptionalBoostHolder", "Class with optional member")
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.def(py::init<>())
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.def_readonly("member", &opt_boost_holder::member)
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.def("member_initialized", &opt_boost_holder::member_initialized);
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using opt_boost_props = OptionalProperties<boost::optional>;
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pybind11::class_<opt_boost_props>(m, "OptionalBoostProperties")
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.def(pybind11::init<>())
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.def_property_readonly("access_by_ref", &opt_boost_props::access_by_ref)
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.def_property_readonly("access_by_copy", &opt_boost_props::access_by_copy);
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#endif
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// test_refsensitive_optional
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using refsensitive_opt_int = ReferenceSensitiveOptional<int>;
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using refsensitive_opt_no_assign = ReferenceSensitiveOptional<NoAssign>;
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m.def("double_or_zero_refsensitive", [](const refsensitive_opt_int& x) -> int {
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return (x ? x.value() : 0) * 2;
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});
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m.def("half_or_none_refsensitive", [](int x) -> refsensitive_opt_int {
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return x != 0 ? refsensitive_opt_int(x / 2) : refsensitive_opt_int();
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});
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// NOLINTNEXTLINE(performance-unnecessary-value-param)
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m.def("test_nullopt_refsensitive", [](refsensitive_opt_int x) {
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return x ? x.value() : 42;
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}, py::arg_v("x", refsensitive_opt_int(), "None"));
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m.def("test_no_assign_refsensitive", [](const refsensitive_opt_no_assign &x) {
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return x ? x->value : 42;
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}, py::arg_v("x", refsensitive_opt_no_assign(), "None"));
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using opt_refsensitive_holder = OptionalHolder<ReferenceSensitiveOptional, MoveOutDetector>;
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py::class_<opt_refsensitive_holder>(m, "OptionalRefSensitiveHolder", "Class with optional member")
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.def(py::init<>())
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.def_readonly("member", &opt_refsensitive_holder::member)
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.def("member_initialized", &opt_refsensitive_holder::member_initialized);
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using opt_refsensitive_props = OptionalProperties<ReferenceSensitiveOptional>;
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pybind11::class_<opt_refsensitive_props>(m, "OptionalRefSensitiveProperties")
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.def(pybind11::init<>())
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.def_property_readonly("access_by_ref", &opt_refsensitive_props::access_by_ref)
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.def_property_readonly("access_by_copy", &opt_refsensitive_props::access_by_copy);
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#ifdef PYBIND11_HAS_FILESYSTEM
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// test_fs_path
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m.attr("has_filesystem") = true;
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@ -280,8 +459,12 @@ TEST_SUBMODULE(stl, m) {
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m.def("tpl_ctor_set", [](std::unordered_set<TplCtorClass> &) {});
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#if defined(PYBIND11_HAS_OPTIONAL)
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m.def("tpl_constr_optional", [](std::optional<TplCtorClass> &) {});
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#elif defined(PYBIND11_HAS_EXP_OPTIONAL)
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m.def("tpl_constr_optional", [](std::experimental::optional<TplCtorClass> &) {});
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#endif
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#if defined(PYBIND11_HAS_EXP_OPTIONAL)
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m.def("tpl_constr_optional_exp", [](std::experimental::optional<TplCtorClass> &) {});
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#endif
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#if defined(PYBIND11_TEST_BOOST)
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m.def("tpl_constr_optional_boost", [](boost::optional<TplCtorClass> &) {});
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#endif
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// test_vec_of_reference_wrapper
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@ -132,6 +132,10 @@ def test_optional():
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assert mvalue.initialized
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assert holder.member_initialized()
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props = m.OptionalProperties()
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assert int(props.access_by_ref) == 42
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assert int(props.access_by_copy) == 42
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@pytest.mark.skipif(
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not hasattr(m, "has_exp_optional"), reason="no <experimental/optional>"
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@ -160,6 +164,69 @@ def test_exp_optional():
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assert mvalue.initialized
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assert holder.member_initialized()
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props = m.OptionalExpProperties()
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assert int(props.access_by_ref) == 42
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assert int(props.access_by_copy) == 42
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@pytest.mark.skipif(not hasattr(m, "has_boost_optional"), reason="no <boost/optional>")
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def test_boost_optional():
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assert m.double_or_zero_boost(None) == 0
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assert m.double_or_zero_boost(42) == 84
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pytest.raises(TypeError, m.double_or_zero_boost, "foo")
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assert m.half_or_none_boost(0) is None
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assert m.half_or_none_boost(42) == 21
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pytest.raises(TypeError, m.half_or_none_boost, "foo")
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assert m.test_nullopt_boost() == 42
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assert m.test_nullopt_boost(None) == 42
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assert m.test_nullopt_boost(42) == 42
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assert m.test_nullopt_boost(43) == 43
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assert m.test_no_assign_boost() == 42
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assert m.test_no_assign_boost(None) == 42
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assert m.test_no_assign_boost(m.NoAssign(43)) == 43
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pytest.raises(TypeError, m.test_no_assign_boost, 43)
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holder = m.OptionalBoostHolder()
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mvalue = holder.member
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assert mvalue.initialized
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assert holder.member_initialized()
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props = m.OptionalBoostProperties()
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assert int(props.access_by_ref) == 42
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assert int(props.access_by_copy) == 42
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def test_reference_sensitive_optional():
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assert m.double_or_zero_refsensitive(None) == 0
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assert m.double_or_zero_refsensitive(42) == 84
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pytest.raises(TypeError, m.double_or_zero_refsensitive, "foo")
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assert m.half_or_none_refsensitive(0) is None
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assert m.half_or_none_refsensitive(42) == 21
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pytest.raises(TypeError, m.half_or_none_refsensitive, "foo")
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assert m.test_nullopt_refsensitive() == 42
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assert m.test_nullopt_refsensitive(None) == 42
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assert m.test_nullopt_refsensitive(42) == 42
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assert m.test_nullopt_refsensitive(43) == 43
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assert m.test_no_assign_refsensitive() == 42
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assert m.test_no_assign_refsensitive(None) == 42
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assert m.test_no_assign_refsensitive(m.NoAssign(43)) == 43
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pytest.raises(TypeError, m.test_no_assign_refsensitive, 43)
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holder = m.OptionalRefSensitiveHolder()
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mvalue = holder.member
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assert mvalue.initialized
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assert holder.member_initialized()
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props = m.OptionalRefSensitiveProperties()
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assert int(props.access_by_ref) == 42
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assert int(props.access_by_copy) == 42
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@pytest.mark.skipif(not hasattr(m, "has_filesystem"), reason="no <filesystem>")
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def test_fs_path():
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