Merge branch 'master' into stable

tests/test_numpy_vectorize.py

 # -*- coding: utf-8 -*-
 import pytest
+
 from pybind11_tests import numpy_vectorize as m
 
 np = pytest.importorskip("numpy")

tests/test_opaque_types.py

 # -*- coding: utf-8 -*-
 import pytest
-from pybind11_tests import opaque_types as m
+
 from pybind11_tests import ConstructorStats, UserType
+from pybind11_tests import opaque_types as m
 
 
 def test_string_list():

tests/test_operator_overloading.py

 # -*- coding: utf-8 -*-
 import pytest
-from pybind11_tests import operators as m
+
 from pybind11_tests import ConstructorStats
+from pybind11_tests import operators as m
 
 
 def test_operator_overloading():

tests/test_pickling.cpp

@@ -67,7 +67,7 @@ TEST_SUBMODULE(pickling, m) {
     // test_roundtrip
     class Pickleable {
     public:
-        Pickleable(const std::string &value) : m_value(value) { }
+        explicit Pickleable(const std::string &value) : m_value(value) { }
         const std::string &value() const { return m_value; }
 
         void setExtra1(int extra1) { m_extra1 = extra1; }
@@ -132,7 +132,7 @@ TEST_SUBMODULE(pickling, m) {
     // test_roundtrip_with_dict
     class PickleableWithDict {
     public:
-        PickleableWithDict(const std::string &value) : value(value) { }
+        explicit PickleableWithDict(const std::string &value) : value(value) { }
 
         std::string value;
         int extra;

tests/test_pickling.py

@@ -2,7 +2,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import pickling as m
 
 try:

tests/test_pytypes.cpp

@@ -20,6 +20,11 @@ TEST_SUBMODULE(pytypes, m) {
     // test_iterable
     m.def("get_iterable", []{return py::iterable();});
     // test_list
+    m.def("list_no_args", []() { return py::list{}; });
+    m.def("list_ssize_t", []() { return py::list{(py::ssize_t) 0}; });
+    m.def("list_size_t", []() { return py::list{(py::size_t) 0}; });
+    m.def("list_insert_ssize_t", [](py::list *l) { return l->insert((py::ssize_t) 1, 83); });
+    m.def("list_insert_size_t", [](py::list *l) { return l->insert((py::size_t) 3, 57); });
     m.def("get_list", []() {
         py::list list;
         list.append("value");
@@ -70,7 +75,25 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("dict_contains",
           [](const py::dict &dict, const char *val) { return dict.contains(val); });
 
+    // test_tuple
+    m.def("tuple_no_args", []() { return py::tuple{}; });
+    m.def("tuple_ssize_t", []() { return py::tuple{(py::ssize_t) 0}; });
+    m.def("tuple_size_t", []() { return py::tuple{(py::size_t) 0}; });
+    m.def("get_tuple", []() { return py::make_tuple(42, py::none(), "spam"); });
+
+#if PY_VERSION_HEX >= 0x03030000
+    // test_simple_namespace
+    m.def("get_simple_namespace", []() {
+        auto ns = py::make_simple_namespace("attr"_a=42, "x"_a="foo", "wrong"_a=1);
+        py::delattr(ns, "wrong");
+        py::setattr(ns, "right", py::int_(2));
+        return ns;
+    });
+#endif
+
     // test_str
+    m.def("str_from_char_ssize_t", []() { return py::str{"red", (py::ssize_t) 3}; });
+    m.def("str_from_char_size_t", []() { return py::str{"blue", (py::size_t) 4}; });
     m.def("str_from_string", []() { return py::str(std::string("baz")); });
     m.def("str_from_bytes", []() { return py::str(py::bytes("boo", 3)); });
     m.def("str_from_object", [](const py::object& obj) { return py::str(obj); });
@@ -87,10 +110,14 @@ TEST_SUBMODULE(pytypes, m) {
     });
 
     // test_bytes
+    m.def("bytes_from_char_ssize_t", []() { return py::bytes{"green", (py::ssize_t) 5}; });
+    m.def("bytes_from_char_size_t", []() { return py::bytes{"purple", (py::size_t) 6}; });
     m.def("bytes_from_string", []() { return py::bytes(std::string("foo")); });
     m.def("bytes_from_str", []() { return py::bytes(py::str("bar", 3)); });
 
     // test bytearray
+    m.def("bytearray_from_char_ssize_t", []() { return py::bytearray{"$%", (py::ssize_t) 2}; });
+    m.def("bytearray_from_char_size_t", []() { return py::bytearray{"@$!", (py::size_t) 3}; });
     m.def("bytearray_from_string", []() { return py::bytearray(std::string("foo")); });
     m.def("bytearray_size", []() { return py::bytearray("foo").size(); });
 
@@ -434,4 +461,100 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("weakref_from_object", [](const py::object &o) { return py::weakref(o); });
     m.def("weakref_from_object_and_function",
           [](py::object o, py::function f) { return py::weakref(std::move(o), std::move(f)); });
+
+// See PR #3263 for background (https://github.com/pybind/pybind11/pull/3263):
+// pytypes.h could be changed to enforce the "most correct" user code below, by removing
+// `const` from iterator `reference` using type aliases, but that will break existing
+// user code.
+#if (defined(__APPLE__) && defined(__clang__)) || defined(PYPY_VERSION)
+// This is "most correct" and enforced on these platforms.
+#    define PYBIND11_AUTO_IT auto it
+#else
+// This works on many platforms and is (unfortunately) reflective of existing user code.
+// NOLINTNEXTLINE(bugprone-macro-parentheses)
+#    define PYBIND11_AUTO_IT auto &it
+#endif
+
+    m.def("tuple_iterator", []() {
+        auto tup = py::make_tuple(5, 7);
+        int tup_sum = 0;
+        for (PYBIND11_AUTO_IT : tup) {
+            tup_sum += it.cast<int>();
+        }
+        return tup_sum;
+    });
+
+    m.def("dict_iterator", []() {
+        py::dict dct;
+        dct[py::int_(3)] = 5;
+        dct[py::int_(7)] = 11;
+        int kv_sum = 0;
+        for (PYBIND11_AUTO_IT : dct) {
+            kv_sum += it.first.cast<int>() * 100 + it.second.cast<int>();
+        }
+        return kv_sum;
+    });
+
+    m.def("passed_iterator", [](const py::iterator &py_it) {
+        int elem_sum = 0;
+        for (PYBIND11_AUTO_IT : py_it) {
+            elem_sum += it.cast<int>();
+        }
+        return elem_sum;
+    });
+
+#undef PYBIND11_AUTO_IT
+
+    // Tests below this line are for pybind11 IMPLEMENTATION DETAILS:
+
+    m.def("sequence_item_get_ssize_t", [](const py::object &o) {
+        return py::detail::accessor_policies::sequence_item::get(o, (py::ssize_t) 1);
+    });
+    m.def("sequence_item_set_ssize_t", [](const py::object &o) {
+        auto s = py::str{"peppa", 5};
+        py::detail::accessor_policies::sequence_item::set(o, (py::ssize_t) 1, s);
+    });
+    m.def("sequence_item_get_size_t", [](const py::object &o) {
+        return py::detail::accessor_policies::sequence_item::get(o, (py::size_t) 2);
+    });
+    m.def("sequence_item_set_size_t", [](const py::object &o) {
+        auto s = py::str{"george", 6};
+        py::detail::accessor_policies::sequence_item::set(o, (py::size_t) 2, s);
+    });
+    m.def("list_item_get_ssize_t", [](const py::object &o) {
+        return py::detail::accessor_policies::list_item::get(o, (py::ssize_t) 3);
+    });
+    m.def("list_item_set_ssize_t", [](const py::object &o) {
+        auto s = py::str{"rebecca", 7};
+        py::detail::accessor_policies::list_item::set(o, (py::ssize_t) 3, s);
+    });
+    m.def("list_item_get_size_t", [](const py::object &o) {
+        return py::detail::accessor_policies::list_item::get(o, (py::size_t) 4);
+    });
+    m.def("list_item_set_size_t", [](const py::object &o) {
+        auto s = py::str{"richard", 7};
+        py::detail::accessor_policies::list_item::set(o, (py::size_t) 4, s);
+    });
+    m.def("tuple_item_get_ssize_t", [](const py::object &o) {
+        return py::detail::accessor_policies::tuple_item::get(o, (py::ssize_t) 5);
+    });
+    m.def("tuple_item_set_ssize_t", []() {
+        auto s0 = py::str{"emely", 5};
+        auto s1 = py::str{"edmond", 6};
+        auto o = py::tuple{2};
+        py::detail::accessor_policies::tuple_item::set(o, (py::ssize_t) 0, s0);
+        py::detail::accessor_policies::tuple_item::set(o, (py::ssize_t) 1, s1);
+        return o;
+    });
+    m.def("tuple_item_get_size_t", [](const py::object &o) {
+        return py::detail::accessor_policies::tuple_item::get(o, (py::size_t) 6);
+    });
+    m.def("tuple_item_set_size_t", []() {
+        auto s0 = py::str{"candy", 5};
+        auto s1 = py::str{"cat", 3};
+        auto o = py::tuple{2};
+        py::detail::accessor_policies::tuple_item::set(o, (py::size_t) 1, s1);
+        py::detail::accessor_policies::tuple_item::set(o, (py::size_t) 0, s0);
+        return o;
+    });
 }

tests/test_pytypes.py

 # -*- coding: utf-8 -*-
 from __future__ import division
-import pytest
+
 import sys
 
-import env  # noqa: F401
+import pytest
 
-from pybind11_tests import pytypes as m
+import env  # noqa: F401
 from pybind11_tests import debug_enabled
+from pybind11_tests import pytypes as m
 
 
 def test_int(doc):
@@ -22,6 +23,15 @@ def test_iterable(doc):
 
 
 def test_list(capture, doc):
+    assert m.list_no_args() == []
+    assert m.list_ssize_t() == []
+    assert m.list_size_t() == []
+    lins = [1, 2]
+    m.list_insert_ssize_t(lins)
+    assert lins == [1, 83, 2]
+    m.list_insert_size_t(lins)
+    assert lins == [1, 83, 2, 57]
+
     with capture:
         lst = m.get_list()
         assert lst == ["inserted-0", "overwritten", "inserted-2"]
@@ -98,7 +108,25 @@ def test_dict(capture, doc):
     assert m.dict_keyword_constructor() == {"x": 1, "y": 2, "z": 3}
 
 
+def test_tuple():
+    assert m.tuple_no_args() == ()
+    assert m.tuple_ssize_t() == ()
+    assert m.tuple_size_t() == ()
+    assert m.get_tuple() == (42, None, "spam")
+
+
+@pytest.mark.skipif("env.PY2")
+def test_simple_namespace():
+    ns = m.get_simple_namespace()
+    assert ns.attr == 42
+    assert ns.x == "foo"
+    assert ns.right == 2
+    assert not hasattr(ns, "wrong")
+
+
 def test_str(doc):
+    assert m.str_from_char_ssize_t().encode().decode() == "red"
+    assert m.str_from_char_size_t().encode().decode() == "blue"
     assert m.str_from_string().encode().decode() == "baz"
     assert m.str_from_bytes().encode().decode() == "boo"
 
@@ -143,6 +171,8 @@ def test_str(doc):
 
 
 def test_bytes(doc):
+    assert m.bytes_from_char_ssize_t().decode() == "green"
+    assert m.bytes_from_char_size_t().decode() == "purple"
     assert m.bytes_from_string().decode() == "foo"
     assert m.bytes_from_str().decode() == "bar"
 
@@ -152,6 +182,8 @@ def test_bytes(doc):
 
 
 def test_bytearray(doc):
+    assert m.bytearray_from_char_ssize_t().decode() == "$%"
+    assert m.bytearray_from_char_size_t().decode() == "@$!"
     assert m.bytearray_from_string().decode() == "foo"
     assert m.bytearray_size() == len("foo")
 
@@ -435,7 +467,8 @@ def test_issue2361():
     assert m.issue2361_str_implicit_copy_none() == "None"
     with pytest.raises(TypeError) as excinfo:
         assert m.issue2361_dict_implicit_copy_none()
-    assert "'NoneType' object is not iterable" in str(excinfo.value)
+    assert "NoneType" in str(excinfo.value)
+    assert "iterable" in str(excinfo.value)
 
 
 @pytest.mark.parametrize(
@@ -589,3 +622,30 @@ def test_weakref(create_weakref, create_weakref_with_callback):
     del obj
     pytest.gc_collect()
     assert callback.called
+
+
+def test_cpp_iterators():
+    assert m.tuple_iterator() == 12
+    assert m.dict_iterator() == 305 + 711
+    assert m.passed_iterator(iter((-7, 3))) == -4
+
+
+def test_implementation_details():
+    lst = [39, 43, 92, 49, 22, 29, 93, 98, 26, 57, 8]
+    tup = tuple(lst)
+    assert m.sequence_item_get_ssize_t(lst) == 43
+    assert m.sequence_item_set_ssize_t(lst) is None
+    assert lst[1] == "peppa"
+    assert m.sequence_item_get_size_t(lst) == 92
+    assert m.sequence_item_set_size_t(lst) is None
+    assert lst[2] == "george"
+    assert m.list_item_get_ssize_t(lst) == 49
+    assert m.list_item_set_ssize_t(lst) is None
+    assert lst[3] == "rebecca"
+    assert m.list_item_get_size_t(lst) == 22
+    assert m.list_item_set_size_t(lst) is None
+    assert lst[4] == "richard"
+    assert m.tuple_item_get_ssize_t(tup) == 29
+    assert m.tuple_item_set_ssize_t() == ("emely", "edmond")
+    assert m.tuple_item_get_size_t(tup) == 93
+    assert m.tuple_item_set_size_t() == ("candy", "cat")

tests/test_sequences_and_iterators.cpp

@@ -15,12 +15,18 @@
 
 #include <algorithm>
 #include <utility>
+#include <vector>
+
+#ifdef PYBIND11_HAS_OPTIONAL
+#include <optional>
+#endif  // PYBIND11_HAS_OPTIONAL
+
 
 template<typename T>
 class NonZeroIterator {
     const T* ptr_;
 public:
-    NonZeroIterator(const T* ptr) : ptr_(ptr) {}
+    explicit NonZeroIterator(const T *ptr) : ptr_(ptr) {}
     const T& operator*() const { return *ptr_; }
     NonZeroIterator& operator++() { ++ptr_; return *this; }
 };
@@ -32,6 +38,29 @@ bool operator==(const NonZeroIterator<std::pair<A, B>>& it, const NonZeroSentine
     return !(*it).first || !(*it).second;
 }
 
+class NonCopyableInt {
+public:
+    explicit NonCopyableInt(int value) : value_(value) {}
+    NonCopyableInt(const NonCopyableInt &) = delete;
+    NonCopyableInt(NonCopyableInt &&other) noexcept : value_(other.value_) {
+        other.value_ = -1;  // detect when an unwanted move occurs
+    }
+    NonCopyableInt &operator=(const NonCopyableInt &) = delete;
+    NonCopyableInt &operator=(NonCopyableInt &&other) noexcept {
+        value_ = other.value_;
+        other.value_ = -1;  // detect when an unwanted move occurs
+        return *this;
+    }
+    int get() const { return value_; }
+    void set(int value) { value_ = value; }
+    ~NonCopyableInt() = default;
+private:
+    int value_;
+};
+using NonCopyableIntPair = std::pair<NonCopyableInt, NonCopyableInt>;
+PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableInt>);
+PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableIntPair>);
+
 template <typename PythonType>
 py::list test_random_access_iterator(PythonType x) {
     if (x.size() < 5)
@@ -77,9 +106,9 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     // test_sliceable
     class Sliceable{
     public:
-      Sliceable(int n): size(n) {}
-      int start,stop,step;
-      int size;
+        explicit Sliceable(int n) : size(n) {}
+        int start, stop, step;
+        int size;
     };
     py::class_<Sliceable>(m, "Sliceable")
         .def(py::init<int>())
@@ -93,15 +122,27 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
             return std::make_tuple(istart, istop, istep);
         });
 
+    m.def("make_forward_slice_size_t", []() { return py::slice(0, -1, 1); });
+    m.def("make_reversed_slice_object", []() { return py::slice(py::none(), py::none(), py::int_(-1)); });
+#ifdef PYBIND11_HAS_OPTIONAL
+    m.attr("has_optional") = true;
+    m.def("make_reversed_slice_size_t_optional_verbose", []() { return py::slice(std::nullopt, std::nullopt, -1); });
+    // Warning: The following spelling may still compile if optional<> is not present and give wrong answers.
+    // Please use with caution.
+    m.def("make_reversed_slice_size_t_optional", []() { return py::slice({}, {}, -1); });
+#else
+    m.attr("has_optional") = false;
+#endif
+
     // test_sequence
     class Sequence {
     public:
-        Sequence(size_t size) : m_size(size) {
+        explicit Sequence(size_t size) : m_size(size) {
             print_created(this, "of size", m_size);
             m_data = new float[size];
             memset(m_data, 0, sizeof(float) * size);
         }
-        Sequence(const std::vector<float> &value) : m_size(value.size()) {
+        explicit Sequence(const std::vector<float> &value) : m_size(value.size()) {
             print_created(this, "of size", m_size, "from std::vector");
             m_data = new float[m_size];
             memcpy(m_data, &value[0], sizeof(float) * m_size);
@@ -239,7 +280,7 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
     class StringMap {
     public:
         StringMap() = default;
-        StringMap(std::unordered_map<std::string, std::string> init)
+        explicit StringMap(std::unordered_map<std::string, std::string> init)
             : map(std::move(init)) {}
 
         void set(const std::string &key, std::string val) { map[key] = std::move(val); }
@@ -271,13 +312,19 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def(
             "items",
             [](const StringMap &map) { return py::make_iterator(map.begin(), map.end()); },
+            py::keep_alive<0, 1>())
+        .def(
+            "values",
+            [](const StringMap &map) { return py::make_value_iterator(map.begin(), map.end()); },
             py::keep_alive<0, 1>());
 
     // test_generalized_iterators
     class IntPairs {
     public:
-        IntPairs(std::vector<std::pair<int, int>> data) : data_(std::move(data)) {}
+        explicit IntPairs(std::vector<std::pair<int, int>> data) : data_(std::move(data)) {}
         const std::pair<int, int>* begin() const { return data_.data(); }
+        // .end() only required for py::make_iterator(self) overload
+        const std::pair<int, int>* end() const { return data_.data() + data_.size(); }
     private:
         std::vector<std::pair<int, int>> data_;
     };
@@ -289,8 +336,62 @@ TEST_SUBMODULE(sequences_and_iterators, m) {
         .def("nonzero_keys", [](const IntPairs& s) {
             return py::make_key_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
         }, py::keep_alive<0, 1>())
+        .def("nonzero_values", [](const IntPairs& s) {
+            return py::make_value_iterator(NonZeroIterator<std::pair<int, int>>(s.begin()), NonZeroSentinel());
+        }, py::keep_alive<0, 1>())
+
+        // test single-argument make_iterator
+        .def("simple_iterator", [](IntPairs& self) {
+            return py::make_iterator(self);
+        }, py::keep_alive<0, 1>())
+        .def("simple_keys", [](IntPairs& self) {
+            return py::make_key_iterator(self);
+        }, py::keep_alive<0, 1>())
+        .def("simple_values", [](IntPairs& self) {
+            return py::make_value_iterator(self);
+        }, py::keep_alive<0, 1>())
+
+        // Test iterator with an Extra (doesn't do anything useful, so not used
+        // at runtime, but tests need to be able to compile with the correct
+        // overload. See PR #3293.
+        .def("_make_iterator_extras", [](IntPairs& self) {
+            return py::make_iterator(self, py::call_guard<int>());
+        }, py::keep_alive<0, 1>())
+        .def("_make_key_extras", [](IntPairs& self) {
+            return py::make_key_iterator(self, py::call_guard<int>());
+        }, py::keep_alive<0, 1>())
+        .def("_make_value_extras", [](IntPairs& self) {
+            return py::make_value_iterator(self, py::call_guard<int>());
+        }, py::keep_alive<0, 1>())
         ;
 
+    // test_iterater_referencing
+    py::class_<NonCopyableInt>(m, "NonCopyableInt")
+        .def(py::init<int>())
+        .def("set", &NonCopyableInt::set)
+        .def("__int__", &NonCopyableInt::get)
+        ;
+    py::class_<std::vector<NonCopyableInt>>(m, "VectorNonCopyableInt")
+        .def(py::init<>())
+        .def("append", [](std::vector<NonCopyableInt> &vec, int value) {
+            vec.emplace_back(value);
+        })
+        .def("__iter__", [](std::vector<NonCopyableInt> &vec) {
+            return py::make_iterator(vec.begin(), vec.end());
+        })
+        ;
+    py::class_<std::vector<NonCopyableIntPair>>(m, "VectorNonCopyableIntPair")
+        .def(py::init<>())
+        .def("append", [](std::vector<NonCopyableIntPair> &vec, const std::pair<int, int> &value) {
+            vec.emplace_back(NonCopyableInt(value.first), NonCopyableInt(value.second));
+        })
+        .def("keys", [](std::vector<NonCopyableIntPair> &vec) {
+            return py::make_key_iterator(vec.begin(), vec.end());
+        })
+        .def("values", [](std::vector<NonCopyableIntPair> &vec) {
+            return py::make_value_iterator(vec.begin(), vec.end());
+        })
+        ;
 
 #if 0
     // Obsolete: special data structure for exposing custom iterator types to python

tests/test_sequences_and_iterators.py

 # -*- coding: utf-8 -*-
 import pytest
-from pybind11_tests import sequences_and_iterators as m
+
 from pybind11_tests import ConstructorStats
+from pybind11_tests import sequences_and_iterators as m
 
 
 def isclose(a, b, rel_tol=1e-05, abs_tol=0.0):
@@ -15,6 +16,17 @@ def allclose(a_list, b_list, rel_tol=1e-05, abs_tol=0.0):
     )
 
 
+def test_slice_constructors():
+    assert m.make_forward_slice_size_t() == slice(0, -1, 1)
+    assert m.make_reversed_slice_object() == slice(None, None, -1)
+
+
+@pytest.mark.skipif(not m.has_optional, reason="no <optional>")
+def test_slice_constructors_explicit_optional():
+    assert m.make_reversed_slice_size_t_optional() == slice(None, None, -1)
+    assert m.make_reversed_slice_size_t_optional_verbose() == slice(None, None, -1)
+
+
 def test_generalized_iterators():
     assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).nonzero()) == [(1, 2), (3, 4)]
     assert list(m.IntPairs([(1, 2), (2, 0), (0, 3), (4, 5)]).nonzero()) == [(1, 2)]
@@ -24,6 +36,10 @@ def test_generalized_iterators():
     assert list(m.IntPairs([(1, 2), (2, 0), (0, 3), (4, 5)]).nonzero_keys()) == [1]
     assert list(m.IntPairs([(0, 3), (1, 2), (3, 4)]).nonzero_keys()) == []
 
+    assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).nonzero_values()) == [2, 4]
+    assert list(m.IntPairs([(1, 2), (2, 0), (0, 3), (4, 5)]).nonzero_values()) == [2]
+    assert list(m.IntPairs([(0, 3), (1, 2), (3, 4)]).nonzero_values()) == []
+
     # __next__ must continue to raise StopIteration
     it = m.IntPairs([(0, 0)]).nonzero()
     for _ in range(3):
@@ -36,6 +52,40 @@ def test_generalized_iterators():
             next(it)
 
 
+def test_generalized_iterators_simple():
+    assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).simple_iterator()) == [
+        (1, 2),
+        (3, 4),
+        (0, 5),
+    ]
+    assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).simple_keys()) == [1, 3, 0]
+    assert list(m.IntPairs([(1, 2), (3, 4), (0, 5)]).simple_values()) == [2, 4, 5]
+
+
+def test_iterator_referencing():
+    """Test that iterators reference rather than copy their referents."""
+    vec = m.VectorNonCopyableInt()
+    vec.append(3)
+    vec.append(5)
+    assert [int(x) for x in vec] == [3, 5]
+    # Increment everything to make sure the referents can be mutated
+    for x in vec:
+        x.set(int(x) + 1)
+    assert [int(x) for x in vec] == [4, 6]
+
+    vec = m.VectorNonCopyableIntPair()
+    vec.append([3, 4])
+    vec.append([5, 7])
+    assert [int(x) for x in vec.keys()] == [3, 5]
+    assert [int(x) for x in vec.values()] == [4, 7]
+    for x in vec.keys():
+        x.set(int(x) + 1)
+    for x in vec.values():
+        x.set(int(x) + 10)
+    assert [int(x) for x in vec.keys()] == [4, 6]
+    assert [int(x) for x in vec.values()] == [14, 17]
+
+
 def test_sliceable():
     sliceable = m.Sliceable(100)
     assert sliceable[::] == (0, 100, 1)
@@ -139,6 +189,7 @@ def test_map_iterator():
         assert sm[k] == expected[k]
     for k, v in sm.items():
         assert v == expected[k]
+    assert list(sm.values()) == [expected[k] for k in sm]
 
     it = iter(m.StringMap({}))
     for _ in range(3):  # __next__ must continue to raise StopIteration

tests/test_smart_ptr.cpp

@@ -24,7 +24,7 @@ template <typename T> class huge_unique_ptr {
     std::unique_ptr<T> ptr;
     uint64_t padding[10];
 public:
-    huge_unique_ptr(T *p) : ptr(p) {}
+    explicit huge_unique_ptr(T *p) : ptr(p) {}
     T *get() { return ptr.get(); }
 };
 
@@ -33,7 +33,7 @@ template <typename T>
 class custom_unique_ptr {
     std::unique_ptr<T> impl;
 public:
-    custom_unique_ptr(T* p) : impl(p) { }
+    explicit custom_unique_ptr(T *p) : impl(p) {}
     T* get() const { return impl.get(); }
     T* release_ptr() { return impl.release(); }
 };
@@ -46,7 +46,7 @@ class shared_ptr_with_addressof_operator {
     std::shared_ptr<T> impl;
 public:
     shared_ptr_with_addressof_operator( ) = default;
-    shared_ptr_with_addressof_operator(T* p) : impl(p) { }
+    explicit shared_ptr_with_addressof_operator(T *p) : impl(p) {}
     T* get() const { return impl.get(); }
     T** operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
 };
@@ -59,7 +59,7 @@ class unique_ptr_with_addressof_operator {
     std::unique_ptr<T> impl;
 public:
     unique_ptr_with_addressof_operator() = default;
-    unique_ptr_with_addressof_operator(T* p) : impl(p) { }
+    explicit unique_ptr_with_addressof_operator(T *p) : impl(p) {}
     T* get() const { return impl.get(); }
     T* release_ptr() { return impl.release(); }
     T** operator&() { throw std::logic_error("Call of overloaded operator& is not expected"); }
@@ -68,7 +68,7 @@ public:
 // Custom object with builtin reference counting (see 'object.h' for the implementation)
 class MyObject1 : public Object {
 public:
-    MyObject1(int value) : value(value) { print_created(this, toString()); }
+    explicit MyObject1(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const override { return "MyObject1[" + std::to_string(value) + "]"; }
 protected:
     ~MyObject1() override { print_destroyed(this); }
@@ -80,7 +80,7 @@ private:
 class MyObject2 {
 public:
     MyObject2(const MyObject2 &) = default;
-    MyObject2(int value) : value(value) { print_created(this, toString()); }
+    explicit MyObject2(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const { return "MyObject2[" + std::to_string(value) + "]"; }
     virtual ~MyObject2() { print_destroyed(this); }
 private:
@@ -91,7 +91,7 @@ private:
 class MyObject3 : public std::enable_shared_from_this<MyObject3> {
 public:
     MyObject3(const MyObject3 &) = default;
-    MyObject3(int value) : value(value) { print_created(this, toString()); }
+    explicit MyObject3(int value) : value(value) { print_created(this, toString()); }
     std::string toString() const { return "MyObject3[" + std::to_string(value) + "]"; }
     virtual ~MyObject3() { print_destroyed(this); }
 private:
@@ -104,7 +104,7 @@ class MyObject4;
 std::unordered_set<MyObject4 *> myobject4_instances;
 class MyObject4 {
 public:
-    MyObject4(int value) : value{value} {
+    explicit MyObject4(int value) : value{value} {
         print_created(this);
         myobject4_instances.insert(this);
     }
@@ -130,7 +130,7 @@ class MyObject4a;
 std::unordered_set<MyObject4a *> myobject4a_instances;
 class MyObject4a {
 public:
-    MyObject4a(int i) {
+    explicit MyObject4a(int i) {
         value = i;
         print_created(this);
         myobject4a_instances.insert(this);
@@ -153,14 +153,14 @@ protected:
 // Object derived but with public destructor and no Deleter in default holder
 class MyObject4b : public MyObject4a {
 public:
-    MyObject4b(int i) : MyObject4a(i) { print_created(this); }
+    explicit MyObject4b(int i) : MyObject4a(i) { print_created(this); }
     ~MyObject4b() override { print_destroyed(this); }
 };
 
 // test_large_holder
 class MyObject5 { // managed by huge_unique_ptr
 public:
-    MyObject5(int value) : value{value} { print_created(this); }
+    explicit MyObject5(int value) : value{value} { print_created(this); }
     ~MyObject5() { print_destroyed(this); }
     int value;
 };
@@ -182,6 +182,7 @@ struct SharedPtrRef {
 struct SharedFromThisRef {
     struct B : std::enable_shared_from_this<B> {
         B() { print_created(this); }
+        // NOLINTNEXTLINE(bugprone-copy-constructor-init)
         B(const B &) : std::enable_shared_from_this<B>() { print_copy_created(this); }
         B(B &&) noexcept : std::enable_shared_from_this<B>() { print_move_created(this); }
         ~B() { print_destroyed(this); }
@@ -221,7 +222,7 @@ struct TypeForHolderWithAddressOf {
 
 // test_move_only_holder_with_addressof_operator
 struct TypeForMoveOnlyHolderWithAddressOf {
-    TypeForMoveOnlyHolderWithAddressOf(int value) : value{value} { print_created(this); }
+    explicit TypeForMoveOnlyHolderWithAddressOf(int value) : value{value} { print_created(this); }
     ~TypeForMoveOnlyHolderWithAddressOf() { print_destroyed(this); }
     std::string toString() const {
         return "MoveOnlyHolderWithAddressOf[" + std::to_string(value) + "]";
@@ -241,7 +242,7 @@ struct ElementBase {
 };
 
 struct ElementA : ElementBase {
-    ElementA(int v) : v(v) { }
+    explicit ElementA(int v) : v(v) {}
     int value() const { return v; }
     int v;
 };
@@ -290,9 +291,9 @@ TEST_SUBMODULE(smart_ptr, m) {
     py::implicitly_convertible<py::int_, MyObject1>();
 
     m.def("make_object_1", []() -> Object * { return new MyObject1(1); });
-    m.def("make_object_2", []() -> ref<Object> { return new MyObject1(2); });
+    m.def("make_object_2", []() -> ref<Object> { return ref<Object>(new MyObject1(2)); });
     m.def("make_myobject1_1", []() -> MyObject1 * { return new MyObject1(4); });
-    m.def("make_myobject1_2", []() -> ref<MyObject1> { return new MyObject1(5); });
+    m.def("make_myobject1_2", []() -> ref<MyObject1> { return ref<MyObject1>(new MyObject1(5)); });
     m.def("print_object_1", [](const Object *obj) { py::print(obj->toString()); });
     m.def("print_object_2", [](ref<Object> obj) { py::print(obj->toString()); });
     m.def("print_object_3", [](const ref<Object> &obj) { py::print(obj->toString()); });
@@ -327,7 +328,7 @@ TEST_SUBMODULE(smart_ptr, m) {
 
     // test_smart_ptr_refcounting
     m.def("test_object1_refcounting", []() {
-        ref<MyObject1> o = new MyObject1(0);
+        auto o = ref<MyObject1>(new MyObject1(0));
         bool good = o->getRefCount() == 1;
         py::object o2 = py::cast(o, py::return_value_policy::reference);
         // always request (partial) ownership for objects with intrusive

tests/test_stl.cpp

@@ -45,7 +45,8 @@ PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>);
 
 /// Issue #528: templated constructor
 struct TplCtorClass {
-    template <typename T> TplCtorClass(const T &) { }
+    template <typename T>
+    explicit TplCtorClass(const T &) {}
     bool operator==(const TplCtorClass &) const { return true; }
 };
 

tests/test_stl.py

 # -*- coding: utf-8 -*-
 import pytest
 
+from pybind11_tests import ConstructorStats, UserType
 from pybind11_tests import stl as m
-from pybind11_tests import UserType
-from pybind11_tests import ConstructorStats
 
 
 def test_vector(doc):

tests/test_stl_binders.cpp

@@ -18,7 +18,7 @@
 class El {
 public:
     El() = delete;
-    El(int v) : a(v) { }
+    explicit El(int v) : a(v) {}
 
     int a;
 };

tests/test_stl_binders.py

@@ -2,7 +2,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import stl_binders as m
 
 
@@ -161,15 +160,43 @@ def test_map_string_double():
     mm["b"] = 2.5
 
     assert list(mm) == ["a", "b"]
-    assert list(mm.items()) == [("a", 1), ("b", 2.5)]
     assert str(mm) == "MapStringDouble{a: 1, b: 2.5}"
+    assert "b" in mm
+    assert "c" not in mm
+    assert 123 not in mm
+
+    # Check that keys, values, items are views, not merely iterable
+    keys = mm.keys()
+    values = mm.values()
+    items = mm.items()
+    assert list(keys) == ["a", "b"]
+    assert len(keys) == 2
+    assert "a" in keys
+    assert "c" not in keys
+    assert 123 not in keys
+    assert list(items) == [("a", 1), ("b", 2.5)]
+    assert len(items) == 2
+    assert ("b", 2.5) in items
+    assert "hello" not in items
+    assert ("b", 2.5, None) not in items
+    assert list(values) == [1, 2.5]
+    assert len(values) == 2
+    assert 1 in values
+    assert 2 not in values
+    # Check that views update when the map is updated
+    mm["c"] = -1
+    assert list(keys) == ["a", "b", "c"]
+    assert list(values) == [1, 2.5, -1]
+    assert list(items) == [("a", 1), ("b", 2.5), ("c", -1)]
 
     um = m.UnorderedMapStringDouble()
     um["ua"] = 1.1
     um["ub"] = 2.6
 
     assert sorted(list(um)) == ["ua", "ub"]
+    assert list(um.keys()) == list(um)
     assert sorted(list(um.items())) == [("ua", 1.1), ("ub", 2.6)]
+    assert list(zip(um.keys(), um.values())) == list(um.items())
     assert "UnorderedMapStringDouble" in str(um)
 
 

tests/test_tagbased_polymorphic.cpp

@@ -37,33 +37,35 @@ struct Animal
 
 struct Dog : Animal
 {
-    Dog(const std::string& _name, Kind _kind = Kind::Dog) : Animal(_name, _kind) {}
+    explicit Dog(const std::string &_name, Kind _kind = Kind::Dog) : Animal(_name, _kind) {}
     std::string bark() const { return name_of_kind(kind) + " " + name + " goes " + sound; }
     std::string sound = "WOOF!";
 };
 
 struct Labrador : Dog
 {
-    Labrador(const std::string& _name, int _excitement = 9001)
+    explicit Labrador(const std::string &_name, int _excitement = 9001)
         : Dog(_name, Kind::Labrador), excitement(_excitement) {}
     int excitement;
 };
 
 struct Chihuahua : Dog
 {
-    Chihuahua(const std::string& _name) : Dog(_name, Kind::Chihuahua) { sound = "iyiyiyiyiyi"; }
+    explicit Chihuahua(const std::string &_name) : Dog(_name, Kind::Chihuahua) {
+        sound = "iyiyiyiyiyi";
+    }
     std::string bark() const { return Dog::bark() + " and runs in circles"; }
 };
 
 struct Cat : Animal
 {
-    Cat(const std::string& _name, Kind _kind = Kind::Cat) : Animal(_name, _kind) {}
+    explicit Cat(const std::string &_name, Kind _kind = Kind::Cat) : Animal(_name, _kind) {}
     std::string purr() const { return "mrowr"; }
 };
 
 struct Panther : Cat
 {
-    Panther(const std::string& _name) : Cat(_name, Kind::Panther) {}
+    explicit Panther(const std::string &_name) : Cat(_name, Kind::Panther) {}
     std::string purr() const { return "mrrrRRRRRR"; }
 };
 
@@ -86,13 +88,13 @@ std::vector<std::unique_ptr<Animal>> create_zoo()
 const std::type_info* Animal::type_of_kind(Kind kind)
 {
     switch (kind) {
-        case Kind::Unknown: break;
-
+        case Kind::Unknown:
         case Kind::Dog: break;
+
         case Kind::Labrador: return &typeid(Labrador);
         case Kind::Chihuahua: return &typeid(Chihuahua);
-        case Kind::LastDog: break;
 
+        case Kind::LastDog:
         case Kind::Cat: break;
         case Kind::Panther: return &typeid(Panther);
         case Kind::LastCat: break;

tests/test_thread.cpp

+/*
+    tests/test_thread.cpp -- call pybind11 bound methods in threads
+
+    Copyright (c) 2021 Laramie Leavitt (Google LLC) <lar@google.com>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#include <pybind11/cast.h>
+#include <pybind11/pybind11.h>
+
+#include <chrono>
+#include <thread>
+
+#include "pybind11_tests.h"
+
+namespace py = pybind11;
+
+namespace {
+
+struct IntStruct {
+    explicit IntStruct(int v) : value(v) {};
+    ~IntStruct() { value = -value; }
+    IntStruct(const IntStruct&) = default;
+    IntStruct& operator=(const IntStruct&) = default;
+
+    int value;
+};
+
+} // namespace
+
+TEST_SUBMODULE(thread, m) {
+
+    py::class_<IntStruct>(m, "IntStruct").def(py::init([](const int i) { return IntStruct(i); }));
+
+    // implicitly_convertible uses loader_life_support when an implicit
+    // conversion is required in order to lifetime extend the reference.
+    //
+    // This test should be run with ASAN for better effectiveness.
+    py::implicitly_convertible<int, IntStruct>();
+
+    m.def("test", [](int expected, const IntStruct &in) {
+        {
+            py::gil_scoped_release release;
+            std::this_thread::sleep_for(std::chrono::milliseconds(5));
+        }
+
+        if (in.value != expected) {
+            throw std::runtime_error("Value changed!!");
+        }
+    });
+
+    m.def(
+        "test_no_gil",
+        [](int expected, const IntStruct &in) {
+            std::this_thread::sleep_for(std::chrono::milliseconds(5));
+            if (in.value != expected) {
+                throw std::runtime_error("Value changed!!");
+            }
+        },
+        py::call_guard<py::gil_scoped_release>());
+
+    // NOTE: std::string_view also uses loader_life_support to ensure that
+    // the string contents remain alive, but that's a C++ 17 feature.
+}

tests/test_thread.py

+# -*- coding: utf-8 -*-
+
+import threading
+
+from pybind11_tests import thread as m
+
+
+class Thread(threading.Thread):
+    def __init__(self, fn):
+        super(Thread, self).__init__()
+        self.fn = fn
+        self.e = None
+
+    def run(self):
+        try:
+            for i in range(10):
+                self.fn(i, i)
+        except Exception as e:
+            self.e = e
+
+    def join(self):
+        super(Thread, self).join()
+        if self.e:
+            raise self.e
+
+
+def test_implicit_conversion():
+    a = Thread(m.test)
+    b = Thread(m.test)
+    c = Thread(m.test)
+    for x in [a, b, c]:
+        x.start()
+    for x in [c, b, a]:
+        x.join()
+
+
+def test_implicit_conversion_no_gil():
+    a = Thread(m.test_no_gil)
+    b = Thread(m.test_no_gil)
+    c = Thread(m.test_no_gil)
+    for x in [a, b, c]:
+        x.start()
+    for x in [c, b, a]:
+        x.join()

tests/test_virtual_functions.cpp

@@ -15,7 +15,7 @@
 /* This is an example class that we'll want to be able to extend from Python */
 class ExampleVirt  {
 public:
-    ExampleVirt(int state) : state(state) { print_created(this, state); }
+    explicit ExampleVirt(int state) : state(state) { print_created(this, state); }
     ExampleVirt(const ExampleVirt &e) : state(e.state) { print_copy_created(this); }
     ExampleVirt(ExampleVirt &&e) noexcept : state(e.state) {
         print_move_created(this);
@@ -454,6 +454,7 @@ template <class Base = B_Tpl>
 class PyB_Tpl : public PyA_Tpl<Base> {
 public:
     using PyA_Tpl<Base>::PyA_Tpl; // Inherit constructors (via PyA_Tpl's inherited constructors)
+    // NOLINTNEXTLINE(bugprone-parent-virtual-call)
     int unlucky_number() override { PYBIND11_OVERRIDE(int, Base, unlucky_number, ); }
     double lucky_number() override { PYBIND11_OVERRIDE(double, Base, lucky_number, ); }
 };

tools/libsize.py

 # -*- coding: utf-8 -*-
-from __future__ import print_function, division
+from __future__ import division, print_function
+
 import os
 import sys
 

tools/make_changelog.py

@@ -4,11 +4,9 @@
 import re
 
 import ghapi.all
-
 from rich import print
 from rich.syntax import Syntax
 
-
 ENTRY = re.compile(
     r"""
     Suggested \s changelog \s entry: