fix: <ranges> support for py::tuple and py::list (#5314)

* feat: add `<ranges>` support for `py::tuple` and `py::list`

* fix: format the code

* fix: disable `ranges` in clang < 16

* refactor: move `<ranges>` test macro to `test_pytypes.h`

* refactor: seperate `ranges` test into 3 funcs

* style: compress the if statement

* style: pre-commit fixes

* style: better formatting

---------

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

include/pybind11/pytypes.h

@@ -1259,6 +1259,7 @@ protected:
     using pointer = arrow_proxy<const handle>;
 
     sequence_fast_readonly(handle obj, ssize_t n) : ptr(PySequence_Fast_ITEMS(obj.ptr()) + n) {}
+    sequence_fast_readonly() = default;
 
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference dereference() const { return *ptr; }
@@ -1281,6 +1282,7 @@ protected:
     using pointer = arrow_proxy<const sequence_accessor>;
 
     sequence_slow_readwrite(handle obj, ssize_t index) : obj(obj), index(index) {}
+    sequence_slow_readwrite() = default;
 
     reference dereference() const { return {obj, static_cast<size_t>(index)}; }
     void increment() { ++index; }

tests/test_pytypes.cpp

@@ -13,6 +13,14 @@
 
 #include <utility>
 
+//__has_include has been part of C++17, no need to check it
+#if defined(PYBIND11_CPP20) && __has_include(<ranges>)
+#    if !defined(PYBIND11_COMPILER_CLANG) || __clang_major__ >= 16 // llvm/llvm-project#52696
+#        define PYBIND11_TEST_PYTYPES_HAS_RANGES
+#        include <ranges>
+#    endif
+#endif
+
 namespace external {
 namespace detail {
 bool check(PyObject *o) { return PyFloat_Check(o) != 0; }
@@ -923,4 +931,59 @@ TEST_SUBMODULE(pytypes, m) {
 #else
     m.attr("defined_PYBIND11_TYPING_H_HAS_STRING_LITERAL") = false;
 #endif
+
+#if defined(PYBIND11_TEST_PYTYPES_HAS_RANGES)
+
+    // test_tuple_ranges
+    m.def("tuple_iterator_default_initialization", []() {
+        using TupleIterator = decltype(std::declval<py::tuple>().begin());
+        static_assert(std::random_access_iterator<TupleIterator>);
+        return TupleIterator{} == TupleIterator{};
+    });
+
+    m.def("transform_tuple_plus_one", [](py::tuple &tpl) {
+        py::list ret{};
+        for (auto it : tpl | std::views::transform([](auto &o) { return py::cast<int>(o) + 1; })) {
+            ret.append(py::int_(it));
+        }
+        return ret;
+    });
+
+    // test_list_ranges
+    m.def("list_iterator_default_initialization", []() {
+        using ListIterator = decltype(std::declval<py::list>().begin());
+        static_assert(std::random_access_iterator<ListIterator>);
+        return ListIterator{} == ListIterator{};
+    });
+
+    m.def("transform_list_plus_one", [](py::list &lst) {
+        py::list ret{};
+        for (auto it : lst | std::views::transform([](auto &o) { return py::cast<int>(o) + 1; })) {
+            ret.append(py::int_(it));
+        }
+        return ret;
+    });
+
+    // test_dict_ranges
+    m.def("dict_iterator_default_initialization", []() {
+        using DictIterator = decltype(std::declval<py::dict>().begin());
+        static_assert(std::forward_iterator<DictIterator>);
+        return DictIterator{} == DictIterator{};
+    });
+
+    m.def("transform_dict_plus_one", [](py::dict &dct) {
+        py::list ret{};
+        for (auto it : dct | std::views::transform([](auto &o) {
+                           return std::pair{py::cast<int>(o.first) + 1,
+                                            py::cast<int>(o.second) + 1};
+                       })) {
+            ret.append(py::make_tuple(py::int_(it.first), py::int_(it.second)));
+        }
+        return ret;
+    });
+
+    m.attr("defined_PYBIND11_TEST_PYTYPES_HAS_RANGES") = true;
+#else
+    m.attr("defined_PYBIND11_TEST_PYTYPES_HAS_RANGES") = false;
+#endif
 }

tests/test_pytypes.py

@@ -1048,3 +1048,45 @@ def test_typevar(doc):
     assert doc(m.annotate_listT_to_T) == "annotate_listT_to_T(arg0: list[T]) -> T"
 
     assert doc(m.annotate_object_to_T) == "annotate_object_to_T(arg0: object) -> T"
+
+
+@pytest.mark.skipif(
+    not m.defined_PYBIND11_TEST_PYTYPES_HAS_RANGES,
+    reason="<ranges> not available.",
+)
+@pytest.mark.parametrize(
+    ("tested_tuple", "expected"),
+    [((1,), [2]), ((3, 4), [4, 5]), ((7, 8, 9), [8, 9, 10])],
+)
+def test_tuple_ranges(tested_tuple, expected):
+    assert m.tuple_iterator_default_initialization()
+    assert m.transform_tuple_plus_one(tested_tuple) == expected
+
+
+@pytest.mark.skipif(
+    not m.defined_PYBIND11_TEST_PYTYPES_HAS_RANGES,
+    reason="<ranges> not available.",
+)
+@pytest.mark.parametrize(
+    ("tested_list", "expected"), [([1], [2]), ([3, 4], [4, 5]), ([7, 8, 9], [8, 9, 10])]
+)
+def test_list_ranges(tested_list, expected):
+    assert m.list_iterator_default_initialization()
+    assert m.transform_list_plus_one(tested_list) == expected
+
+
+@pytest.mark.skipif(
+    not m.defined_PYBIND11_TEST_PYTYPES_HAS_RANGES,
+    reason="<ranges> not available.",
+)
+@pytest.mark.parametrize(
+    ("tested_dict", "expected"),
+    [
+        ({1: 2}, [(2, 3)]),
+        ({3: 4, 5: 6}, [(4, 5), (6, 7)]),
+        ({7: 8, 9: 10, 11: 12}, [(8, 9), (10, 11), (12, 13)]),
+    ],
+)
+def test_dict_ranges(tested_dict, expected):
+    assert m.dict_iterator_default_initialization()
+    assert m.transform_dict_plus_one(tested_dict) == expected