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pybind11/include/pybind11/stl_bind.h
aimir 9db988013c
Correct class names for KeysView, ValuesView and ItemsView in bind_map (#4353) 
* Create templated abstract classes KeysView, ValuesView and ItemsView, and implement them on-the-fly when wrapping any specific map type

* We don't want to wrap different ValuesView objects for double values and const double, for example, as both wrappers will be named ValuesView[float]

* Fallback to C++ names if key or values types are not wrapped

* Added a test for .keys(), .values() and .items() returning the same types for similarly-typed maps

* Fixed wrong use of auto in a declarator list: the two descriptions might have different types

* Fixes for clang-tidy issues: explicit single-argument constructor, using the 'override' keyword when overriding functions

* Bugfix for old versions of clang++, which seem to have trouble with the struct being defined inside a module, which was also needlessly ugly anyway

* Bugfix for clang++, which doesn't have some of the names in runtime uness they are specified to be static

* A fix for clang-tidy performance-inefficient-string-concatenation issues - I personally think this looks uglier, but it's probably worth it for clang-tidy to be happy

* Possible fix for clang++ linking issues - make the descriptions static constexpr to make sure they are known before linking

* Correct names for previously-wrapped types as keys/values of maps

* Bugfix - typo in type info names which caused things to segfault

* Apply suggestions from code review

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

* Use detail::remove_cvref_t instead of doing remove_cv and remove_reference separately

* Avoid names with double underscore, as they are reserved

* Improved testing for KeysView, ValuesView and ItemsView: check type names + stricter asserts

* Moved description logic to helper function in type_caster_base.h

* style: pre-commit fixes

* Fix a clang-tidy issue: do not use 'else' after 'return'

* Apply suggestion by @Skylion007, with additional trivial simplification.

Co-authored-by: Amir <aimir@local>
Co-authored-by: aimir <aimir@localhost>
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>
2022-12-08 23:15:11 -08:00

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/*
pybind11/std_bind.h: Binding generators for STL data types
Copyright (c) 2016 Sergey Lyskov and Wenzel Jakob
All rights reserved. Use of this source code is governed by a
BSD-style license that can be found in the LICENSE file.
*/
#pragma once
#include "detail/common.h"
#include "detail/type_caster_base.h"
#include "cast.h"
#include "operators.h"
#include <algorithm>
#include <sstream>
#include <type_traits>
PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
PYBIND11_NAMESPACE_BEGIN(detail)
/* SFINAE helper class used by 'is_comparable */
template <typename T>
struct container_traits {
template <typename T2>
static std::true_type
test_comparable(decltype(std::declval<const T2 &>() == std::declval<const T2 &>()) *);
template <typename T2>
static std::false_type test_comparable(...);
template <typename T2>
static std::true_type test_value(typename T2::value_type *);
template <typename T2>
static std::false_type test_value(...);
template <typename T2>
static std::true_type test_pair(typename T2::first_type *, typename T2::second_type *);
template <typename T2>
static std::false_type test_pair(...);
static constexpr const bool is_comparable
= std::is_same<std::true_type, decltype(test_comparable<T>(nullptr))>::value;
static constexpr const bool is_pair
= std::is_same<std::true_type, decltype(test_pair<T>(nullptr, nullptr))>::value;
static constexpr const bool is_vector
= std::is_same<std::true_type, decltype(test_value<T>(nullptr))>::value;
static constexpr const bool is_element = !is_pair && !is_vector;
};
/* Default: is_comparable -> std::false_type */
template <typename T, typename SFINAE = void>
struct is_comparable : std::false_type {};
/* For non-map data structures, check whether operator== can be instantiated */
template <typename T>
struct is_comparable<
T,
enable_if_t<container_traits<T>::is_element && container_traits<T>::is_comparable>>
: std::true_type {};
/* For a vector/map data structure, recursively check the value type
(which is std::pair for maps) */
template <typename T>
struct is_comparable<T, enable_if_t<container_traits<T>::is_vector>> {
static constexpr const bool value = is_comparable<typename T::value_type>::value;
};
/* For pairs, recursively check the two data types */
template <typename T>
struct is_comparable<T, enable_if_t<container_traits<T>::is_pair>> {
static constexpr const bool value = is_comparable<typename T::first_type>::value
&& is_comparable<typename T::second_type>::value;
};
/* Fallback functions */
template <typename, typename, typename... Args>
void vector_if_copy_constructible(const Args &...) {}
template <typename, typename, typename... Args>
void vector_if_equal_operator(const Args &...) {}
template <typename, typename, typename... Args>
void vector_if_insertion_operator(const Args &...) {}
template <typename, typename, typename... Args>
void vector_modifiers(const Args &...) {}
template <typename Vector, typename Class_>
void vector_if_copy_constructible(enable_if_t<is_copy_constructible<Vector>::value, Class_> &cl) {
cl.def(init<const Vector &>(), "Copy constructor");
}
template <typename Vector, typename Class_>
void vector_if_equal_operator(enable_if_t<is_comparable<Vector>::value, Class_> &cl) {
using T = typename Vector::value_type;
cl.def(self == self);
cl.def(self != self);
cl.def(
"count",
[](const Vector &v, const T &x) { return std::count(v.begin(), v.end(), x); },
arg("x"),
"Return the number of times ``x`` appears in the list");
cl.def(
"remove",
[](Vector &v, const T &x) {
auto p = std::find(v.begin(), v.end(), x);
if (p != v.end()) {
v.erase(p);
} else {
throw value_error();
}
},
arg("x"),
"Remove the first item from the list whose value is x. "
"It is an error if there is no such item.");
cl.def(
"__contains__",
[](const Vector &v, const T &x) { return std::find(v.begin(), v.end(), x) != v.end(); },
arg("x"),
"Return true the container contains ``x``");
}
// Vector modifiers -- requires a copyable vector_type:
// (Technically, some of these (pop and __delitem__) don't actually require copyability, but it
// seems silly to allow deletion but not insertion, so include them here too.)
template <typename Vector, typename Class_>
void vector_modifiers(
enable_if_t<is_copy_constructible<typename Vector::value_type>::value, Class_> &cl) {
using T = typename Vector::value_type;
using SizeType = typename Vector::size_type;
using DiffType = typename Vector::difference_type;
auto wrap_i = [](DiffType i, SizeType n) {
if (i < 0) {
i += n;
}
if (i < 0 || (SizeType) i >= n) {
throw index_error();
}
return i;
};
cl.def(
"append",
[](Vector &v, const T &value) { v.push_back(value); },
arg("x"),
"Add an item to the end of the list");
cl.def(init([](const iterable &it) {
auto v = std::unique_ptr<Vector>(new Vector());
v->reserve(len_hint(it));
for (handle h : it) {
v->push_back(h.cast<T>());
}
return v.release();
}));
cl.def(
"clear", [](Vector &v) { v.clear(); }, "Clear the contents");
cl.def(
"extend",
[](Vector &v, const Vector &src) { v.insert(v.end(), src.begin(), src.end()); },
arg("L"),
"Extend the list by appending all the items in the given list");
cl.def(
"extend",
[](Vector &v, const iterable &it) {
const size_t old_size = v.size();
v.reserve(old_size + len_hint(it));
try {
for (handle h : it) {
v.push_back(h.cast<T>());
}
} catch (const cast_error &) {
v.erase(v.begin() + static_cast<typename Vector::difference_type>(old_size),
v.end());
try {
v.shrink_to_fit();
} catch (const std::exception &) {
// Do nothing
}
throw;
}
},
arg("L"),
"Extend the list by appending all the items in the given list");
cl.def(
"insert",
[](Vector &v, DiffType i, const T &x) {
// Can't use wrap_i; i == v.size() is OK
if (i < 0) {
i += v.size();
}
if (i < 0 || (SizeType) i > v.size()) {
throw index_error();
}
v.insert(v.begin() + i, x);
},
arg("i"),
arg("x"),
"Insert an item at a given position.");
cl.def(
"pop",
[](Vector &v) {
if (v.empty()) {
throw index_error();
}
T t = std::move(v.back());
v.pop_back();
return t;
},
"Remove and return the last item");
cl.def(
"pop",
[wrap_i](Vector &v, DiffType i) {
i = wrap_i(i, v.size());
T t = std::move(v[(SizeType) i]);
v.erase(std::next(v.begin(), i));
return t;
},
arg("i"),
"Remove and return the item at index ``i``");
cl.def("__setitem__", [wrap_i](Vector &v, DiffType i, const T &t) {
i = wrap_i(i, v.size());
v[(SizeType) i] = t;
});
/// Slicing protocol
cl.def(
"__getitem__",
[](const Vector &v, const slice &slice) -> Vector * {
size_t start = 0, stop = 0, step = 0, slicelength = 0;
if (!slice.compute(v.size(), &start, &stop, &step, &slicelength)) {
throw error_already_set();
}
auto *seq = new Vector();
seq->reserve((size_t) slicelength);
for (size_t i = 0; i < slicelength; ++i) {
seq->push_back(v[start]);
start += step;
}
return seq;
},
arg("s"),
"Retrieve list elements using a slice object");
cl.def(
"__setitem__",
[](Vector &v, const slice &slice, const Vector &value) {
size_t start = 0, stop = 0, step = 0, slicelength = 0;
if (!slice.compute(v.size(), &start, &stop, &step, &slicelength)) {
throw error_already_set();
}
if (slicelength != value.size()) {
throw std::runtime_error(
"Left and right hand size of slice assignment have different sizes!");
}
for (size_t i = 0; i < slicelength; ++i) {
v[start] = value[i];
start += step;
}
},
"Assign list elements using a slice object");
cl.def(
"__delitem__",
[wrap_i](Vector &v, DiffType i) {
i = wrap_i(i, v.size());
v.erase(v.begin() + i);
},
"Delete the list elements at index ``i``");
cl.def(
"__delitem__",
[](Vector &v, const slice &slice) {
size_t start = 0, stop = 0, step = 0, slicelength = 0;
if (!slice.compute(v.size(), &start, &stop, &step, &slicelength)) {
throw error_already_set();
}
if (step == 1 && false) {
v.erase(v.begin() + (DiffType) start, v.begin() + DiffType(start + slicelength));
} else {
for (size_t i = 0; i < slicelength; ++i) {
v.erase(v.begin() + DiffType(start));
start += step - 1;
}
}
},
"Delete list elements using a slice object");
}
// If the type has an operator[] that doesn't return a reference (most notably std::vector<bool>),
// we have to access by copying; otherwise we return by reference.
template <typename Vector>
using vector_needs_copy
= negation<std::is_same<decltype(std::declval<Vector>()[typename Vector::size_type()]),
typename Vector::value_type &>>;
// The usual case: access and iterate by reference
template <typename Vector, typename Class_>
void vector_accessor(enable_if_t<!vector_needs_copy<Vector>::value, Class_> &cl) {
using T = typename Vector::value_type;
using SizeType = typename Vector::size_type;
using DiffType = typename Vector::difference_type;
using ItType = typename Vector::iterator;
auto wrap_i = [](DiffType i, SizeType n) {
if (i < 0) {
i += n;
}
if (i < 0 || (SizeType) i >= n) {
throw index_error();
}
return i;
};
cl.def(
"__getitem__",
[wrap_i](Vector &v, DiffType i) -> T & {
i = wrap_i(i, v.size());
return v[(SizeType) i];
},
return_value_policy::reference_internal // ref + keepalive
);
cl.def(
"__iter__",
[](Vector &v) {
return make_iterator<return_value_policy::reference_internal, ItType, ItType, T &>(
v.begin(), v.end());
},
keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
);
}
// The case for special objects, like std::vector<bool>, that have to be returned-by-copy:
template <typename Vector, typename Class_>
void vector_accessor(enable_if_t<vector_needs_copy<Vector>::value, Class_> &cl) {
using T = typename Vector::value_type;
using SizeType = typename Vector::size_type;
using DiffType = typename Vector::difference_type;
using ItType = typename Vector::iterator;
cl.def("__getitem__", [](const Vector &v, DiffType i) -> T {
if (i < 0 && (i += v.size()) < 0) {
throw index_error();
}
if ((SizeType) i >= v.size()) {
throw index_error();
}
return v[(SizeType) i];
});
cl.def(
"__iter__",
[](Vector &v) {
return make_iterator<return_value_policy::copy, ItType, ItType, T>(v.begin(), v.end());
},
keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
);
}
template <typename Vector, typename Class_>
auto vector_if_insertion_operator(Class_ &cl, std::string const &name)
-> decltype(std::declval<std::ostream &>() << std::declval<typename Vector::value_type>(),
void()) {
using size_type = typename Vector::size_type;
cl.def(
"__repr__",
[name](Vector &v) {
std::ostringstream s;
s << name << '[';
for (size_type i = 0; i < v.size(); ++i) {
s << v[i];
if (i != v.size() - 1) {
s << ", ";
}
}
s << ']';
return s.str();
},
"Return the canonical string representation of this list.");
}
// Provide the buffer interface for vectors if we have data() and we have a format for it
// GCC seems to have "void std::vector<bool>::data()" - doing SFINAE on the existence of data()
// is insufficient, we need to check it returns an appropriate pointer
template <typename Vector, typename = void>
struct vector_has_data_and_format : std::false_type {};
template <typename Vector>
struct vector_has_data_and_format<
Vector,
enable_if_t<std::is_same<decltype(format_descriptor<typename Vector::value_type>::format(),
std::declval<Vector>().data()),
typename Vector::value_type *>::value>> : std::true_type {};
// [workaround(intel)] Separate function required here
// Workaround as the Intel compiler does not compile the enable_if_t part below
// (tested with icc (ICC) 2021.1 Beta 20200827)
template <typename... Args>
constexpr bool args_any_are_buffer() {
return detail::any_of<std::is_same<Args, buffer_protocol>...>::value;
}
// [workaround(intel)] Separate function required here
// [workaround(msvc)] Can't use constexpr bool in return type
// Add the buffer interface to a vector
template <typename Vector, typename Class_, typename... Args>
void vector_buffer_impl(Class_ &cl, std::true_type) {
using T = typename Vector::value_type;
static_assert(vector_has_data_and_format<Vector>::value,
"There is not an appropriate format descriptor for this vector");
// numpy.h declares this for arbitrary types, but it may raise an exception and crash hard
// at runtime if PYBIND11_NUMPY_DTYPE hasn't been called, so check here
format_descriptor<T>::format();
cl.def_buffer([](Vector &v) -> buffer_info {
return buffer_info(v.data(),
static_cast<ssize_t>(sizeof(T)),
format_descriptor<T>::format(),
1,
{v.size()},
{sizeof(T)});
});
cl.def(init([](const buffer &buf) {
auto info = buf.request();
if (info.ndim != 1 || info.strides[0] % static_cast<ssize_t>(sizeof(T))) {
throw type_error("Only valid 1D buffers can be copied to a vector");
}
if (!detail::compare_buffer_info<T>::compare(info)
|| (ssize_t) sizeof(T) != info.itemsize) {
throw type_error("Format mismatch (Python: " + info.format
+ " C++: " + format_descriptor<T>::format() + ")");
}
T *p = static_cast<T *>(info.ptr);
ssize_t step = info.strides[0] / static_cast<ssize_t>(sizeof(T));
T *end = p + info.shape[0] * step;
if (step == 1) {
return Vector(p, end);
}
Vector vec;
vec.reserve((size_t) info.shape[0]);
for (; p != end; p += step) {
vec.push_back(*p);
}
return vec;
}));
return;
}
template <typename Vector, typename Class_, typename... Args>
void vector_buffer_impl(Class_ &, std::false_type) {}
template <typename Vector, typename Class_, typename... Args>
void vector_buffer(Class_ &cl) {
vector_buffer_impl<Vector, Class_, Args...>(
cl, detail::any_of<std::is_same<Args, buffer_protocol>...>{});
}
PYBIND11_NAMESPACE_END(detail)
//
// std::vector
//
template <typename Vector, typename holder_type = std::unique_ptr<Vector>, typename... Args>
class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, Args &&...args) {
using Class_ = class_<Vector, holder_type>;
// If the value_type is unregistered (e.g. a converting type) or is itself registered
// module-local then make the vector binding module-local as well:
using vtype = typename Vector::value_type;
auto *vtype_info = detail::get_type_info(typeid(vtype));
bool local = !vtype_info || vtype_info->module_local;
Class_ cl(scope, name.c_str(), pybind11::module_local(local), std::forward<Args>(args)...);
// Declare the buffer interface if a buffer_protocol() is passed in
detail::vector_buffer<Vector, Class_, Args...>(cl);
cl.def(init<>());
// Register copy constructor (if possible)
detail::vector_if_copy_constructible<Vector, Class_>(cl);
// Register comparison-related operators and functions (if possible)
detail::vector_if_equal_operator<Vector, Class_>(cl);
// Register stream insertion operator (if possible)
detail::vector_if_insertion_operator<Vector, Class_>(cl, name);
// Modifiers require copyable vector value type
detail::vector_modifiers<Vector, Class_>(cl);
// Accessor and iterator; return by value if copyable, otherwise we return by ref + keep-alive
detail::vector_accessor<Vector, Class_>(cl);
cl.def(
"__bool__",
[](const Vector &v) -> bool { return !v.empty(); },
"Check whether the list is nonempty");
cl.def("__len__", &Vector::size);
#if 0
// C++ style functions deprecated, leaving it here as an example
cl.def(init<size_type>());
cl.def("resize",
(void (Vector::*) (size_type count)) & Vector::resize,
"changes the number of elements stored");
cl.def("erase",
[](Vector &v, SizeType i) {
if (i >= v.size())
throw index_error();
v.erase(v.begin() + i);
}, "erases element at index ``i``");
cl.def("empty", &Vector::empty, "checks whether the container is empty");
cl.def("size", &Vector::size, "returns the number of elements");
cl.def("push_back", (void (Vector::*)(const T&)) &Vector::push_back, "adds an element to the end");
cl.def("pop_back", &Vector::pop_back, "removes the last element");
cl.def("max_size", &Vector::max_size, "returns the maximum possible number of elements");
cl.def("reserve", &Vector::reserve, "reserves storage");
cl.def("capacity", &Vector::capacity, "returns the number of elements that can be held in currently allocated storage");
cl.def("shrink_to_fit", &Vector::shrink_to_fit, "reduces memory usage by freeing unused memory");
cl.def("clear", &Vector::clear, "clears the contents");
cl.def("swap", &Vector::swap, "swaps the contents");
cl.def("front", [](Vector &v) {
if (v.size()) return v.front();
else throw index_error();
}, "access the first element");
cl.def("back", [](Vector &v) {
if (v.size()) return v.back();
else throw index_error();
}, "access the last element ");
#endif
return cl;
}
//
// std::map, std::unordered_map
//
PYBIND11_NAMESPACE_BEGIN(detail)
/* Fallback functions */
template <typename, typename, typename... Args>
void map_if_insertion_operator(const Args &...) {}
template <typename, typename, typename... Args>
void map_assignment(const Args &...) {}
// Map assignment when copy-assignable: just copy the value
template <typename Map, typename Class_>
void map_assignment(
enable_if_t<is_copy_assignable<typename Map::mapped_type>::value, Class_> &cl) {
using KeyType = typename Map::key_type;
using MappedType = typename Map::mapped_type;
cl.def("__setitem__", [](Map &m, const KeyType &k, const MappedType &v) {
auto it = m.find(k);
if (it != m.end()) {
it->second = v;
} else {
m.emplace(k, v);
}
});
}
// Not copy-assignable, but still copy-constructible: we can update the value by erasing and
// reinserting
template <typename Map, typename Class_>
void map_assignment(enable_if_t<!is_copy_assignable<typename Map::mapped_type>::value
&& is_copy_constructible<typename Map::mapped_type>::value,
Class_> &cl) {
using KeyType = typename Map::key_type;
using MappedType = typename Map::mapped_type;
cl.def("__setitem__", [](Map &m, const KeyType &k, const MappedType &v) {
// We can't use m[k] = v; because value type might not be default constructable
auto r = m.emplace(k, v);
if (!r.second) {
// value type is not copy assignable so the only way to insert it is to erase it
// first...
m.erase(r.first);
m.emplace(k, v);
}
});
}
template <typename Map, typename Class_>
auto map_if_insertion_operator(Class_ &cl, std::string const &name)
-> decltype(std::declval<std::ostream &>() << std::declval<typename Map::key_type>()
<< std::declval<typename Map::mapped_type>(),
void()) {
cl.def(
"__repr__",
[name](Map &m) {
std::ostringstream s;
s << name << '{';
bool f = false;
for (auto const &kv : m) {
if (f) {
s << ", ";
}
s << kv.first << ": " << kv.second;
f = true;
}
s << '}';
return s.str();
},
"Return the canonical string representation of this map.");
}
template <typename KeyType>
struct keys_view {
virtual size_t len() = 0;
virtual iterator iter() = 0;
virtual bool contains(const KeyType &k) = 0;
virtual bool contains(const object &k) = 0;
virtual ~keys_view() = default;
};
template <typename MappedType>
struct values_view {
virtual size_t len() = 0;
virtual iterator iter() = 0;
virtual ~values_view() = default;
};
template <typename KeyType, typename MappedType>
struct items_view {
virtual size_t len() = 0;
virtual iterator iter() = 0;
virtual ~items_view() = default;
};
template <typename Map, typename KeysView>
struct KeysViewImpl : public KeysView {
explicit KeysViewImpl(Map &map) : map(map) {}
size_t len() override { return map.size(); }
iterator iter() override { return make_key_iterator(map.begin(), map.end()); }
bool contains(const typename Map::key_type &k) override { return map.find(k) != map.end(); }
bool contains(const object &) override { return false; }
Map &map;
};
template <typename Map, typename ValuesView>
struct ValuesViewImpl : public ValuesView {
explicit ValuesViewImpl(Map &map) : map(map) {}
size_t len() override { return map.size(); }
iterator iter() override { return make_value_iterator(map.begin(), map.end()); }
Map &map;
};
template <typename Map, typename ItemsView>
struct ItemsViewImpl : public ItemsView {
explicit ItemsViewImpl(Map &map) : map(map) {}
size_t len() override { return map.size(); }
iterator iter() override { return make_iterator(map.begin(), map.end()); }
Map &map;
};
PYBIND11_NAMESPACE_END(detail)
template <typename Map, typename holder_type = std::unique_ptr<Map>, typename... Args>
class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&...args) {
using KeyType = typename Map::key_type;
using MappedType = typename Map::mapped_type;
using StrippedKeyType = detail::remove_cvref_t<KeyType>;
using StrippedMappedType = detail::remove_cvref_t<MappedType>;
using KeysView = detail::keys_view<StrippedKeyType>;
using ValuesView = detail::values_view<StrippedMappedType>;
using ItemsView = detail::items_view<StrippedKeyType, StrippedMappedType>;
using Class_ = class_<Map, holder_type>;
// If either type is a non-module-local bound type then make the map binding non-local as well;
// otherwise (e.g. both types are either module-local or converting) the map will be
// module-local.
auto *tinfo = detail::get_type_info(typeid(MappedType));
bool local = !tinfo || tinfo->module_local;
if (local) {
tinfo = detail::get_type_info(typeid(KeyType));
local = !tinfo || tinfo->module_local;
}
Class_ cl(scope, name.c_str(), pybind11::module_local(local), std::forward<Args>(args)...);
static constexpr auto key_type_descr = detail::make_caster<KeyType>::name;
static constexpr auto mapped_type_descr = detail::make_caster<MappedType>::name;
std::string key_type_name(key_type_descr.text), mapped_type_name(mapped_type_descr.text);
// If key type isn't properly wrapped, fall back to C++ names
if (key_type_name == "%") {
key_type_name = detail::type_info_description(typeid(KeyType));
}
// Similarly for value type:
if (mapped_type_name == "%") {
mapped_type_name = detail::type_info_description(typeid(MappedType));
}
// Wrap KeysView[KeyType] if it wasn't already wrapped
if (!detail::get_type_info(typeid(KeysView))) {
class_<KeysView> keys_view(
scope, ("KeysView[" + key_type_name + "]").c_str(), pybind11::module_local(local));
keys_view.def("__len__", &KeysView::len);
keys_view.def("__iter__",
&KeysView::iter,
keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
);
keys_view.def("__contains__",
static_cast<bool (KeysView::*)(const KeyType &)>(&KeysView::contains));
// Fallback for when the object is not of the key type
keys_view.def("__contains__",
static_cast<bool (KeysView::*)(const object &)>(&KeysView::contains));
}
// Similarly for ValuesView:
if (!detail::get_type_info(typeid(ValuesView))) {
class_<ValuesView> values_view(scope,
("ValuesView[" + mapped_type_name + "]").c_str(),
pybind11::module_local(local));
values_view.def("__len__", &ValuesView::len);
values_view.def("__iter__",
&ValuesView::iter,
keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
);
}
// Similarly for ItemsView:
if (!detail::get_type_info(typeid(ItemsView))) {
class_<ItemsView> items_view(
scope,
("ItemsView[" + key_type_name + ", ").append(mapped_type_name + "]").c_str(),
pybind11::module_local(local));
items_view.def("__len__", &ItemsView::len);
items_view.def("__iter__",
&ItemsView::iter,
keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
);
}
cl.def(init<>());
// Register stream insertion operator (if possible)
detail::map_if_insertion_operator<Map, Class_>(cl, name);
cl.def(
"__bool__",
[](const Map &m) -> bool { return !m.empty(); },
"Check whether the map is nonempty");
cl.def(
"__iter__",
[](Map &m) { return make_key_iterator(m.begin(), m.end()); },
keep_alive<0, 1>() /* Essential: keep map alive while iterator exists */
);
cl.def(
"keys",
[](Map &m) {
return std::unique_ptr<KeysView>(new detail::KeysViewImpl<Map, KeysView>(m));
},
keep_alive<0, 1>() /* Essential: keep map alive while view exists */
);
cl.def(
"values",
[](Map &m) {
return std::unique_ptr<ValuesView>(new detail::ValuesViewImpl<Map, ValuesView>(m));
},
keep_alive<0, 1>() /* Essential: keep map alive while view exists */
);
cl.def(
"items",
[](Map &m) {
return std::unique_ptr<ItemsView>(new detail::ItemsViewImpl<Map, ItemsView>(m));
},
keep_alive<0, 1>() /* Essential: keep map alive while view exists */
);
cl.def(
"__getitem__",
[](Map &m, const KeyType &k) -> MappedType & {
auto it = m.find(k);
if (it == m.end()) {
throw key_error();
}
return it->second;
},
return_value_policy::reference_internal // ref + keepalive
);
cl.def("__contains__", [](Map &m, const KeyType &k) -> bool {
auto it = m.find(k);
if (it == m.end()) {
return false;
}
return true;
});
// Fallback for when the object is not of the key type
cl.def("__contains__", [](Map &, const object &) -> bool { return false; });
// Assignment provided only if the type is copyable
detail::map_assignment<Map, Class_>(cl);
cl.def("__delitem__", [](Map &m, const KeyType &k) {
auto it = m.find(k);
if (it == m.end()) {
throw key_error();
}
m.erase(it);
});
cl.def("__len__", &Map::size);
return cl;
}
PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
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