Add test_format_descriptor_format

tests/test_buffers.cpp

@@ -7,12 +7,40 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include <pybind11/complex.h>
 #include <pybind11/stl.h>
 
 #include "constructor_stats.h"
 #include "pybind11_tests.h"
 
 TEST_SUBMODULE(buffers, m) {
+
+#define PYBIND11_LOCAL_DEF(...)                                                                   \
+    if (cpp_name == #__VA_ARGS__)                                                                 \
+        return py::format_descriptor<__VA_ARGS__>::format();
+
+    m.def("format_descriptor_format", [](const std::string &cpp_name) {
+        PYBIND11_LOCAL_DEF(PyObject *)
+        PYBIND11_LOCAL_DEF(bool)
+        PYBIND11_LOCAL_DEF(std::int8_t)
+        PYBIND11_LOCAL_DEF(std::uint8_t)
+        PYBIND11_LOCAL_DEF(std::int16_t)
+        PYBIND11_LOCAL_DEF(std::uint16_t)
+        PYBIND11_LOCAL_DEF(std::int32_t)
+        PYBIND11_LOCAL_DEF(std::uint32_t)
+        PYBIND11_LOCAL_DEF(std::int64_t)
+        PYBIND11_LOCAL_DEF(std::uint64_t)
+        PYBIND11_LOCAL_DEF(float)
+        PYBIND11_LOCAL_DEF(double)
+        PYBIND11_LOCAL_DEF(long double)
+        PYBIND11_LOCAL_DEF(std::complex<float>)
+        PYBIND11_LOCAL_DEF(std::complex<double>)
+        PYBIND11_LOCAL_DEF(std::complex<long double>)
+        return std::string("UNKNOWN");
+    });
+
+#undef PYBIND11_LOCAL_DEF
+
     // test_from_python / test_to_python:
     class Matrix {
     public:

tests/test_buffers.py

@@ -11,6 +11,32 @@ from pybind11_tests import buffers as m
 np = pytest.importorskip("numpy")
 
 
+@pytest.mark.parametrize(
+    ("cpp_name", "expected_codes"),
+    [
+        ("PyObject *", ["O"]),
+        ("bool", ["?"]),
+        ("std::int8_t", ["b"]),
+        ("std::uint8_t", ["B"]),
+        ("std::int16_t", ["h"]),
+        ("std::uint16_t", ["H"]),
+        ("std::int32_t", ["i"]),
+        ("std::uint32_t", ["I"]),
+        ("std::int64_t", ["q"]),
+        ("std::uint64_t", ["Q"]),
+        ("float", ["f"]),
+        ("double", ["d"]),
+        ("long double", ["g", "d"]),
+        ("std::complex<float>", ["Zf"]),
+        ("std::complex<double>", ["Zd"]),
+        ("std::complex<long double>", ["Zg", "Zd"]),
+        ("", ["UNKNOWN"]),
+    ],
+)
+def test_format_descriptor_format(cpp_name, expected_codes):
+    assert m.format_descriptor_format(cpp_name) in expected_codes
+
+
 def test_from_python():
     with pytest.raises(RuntimeError) as excinfo:
         m.Matrix(np.array([1, 2, 3]))  # trying to assign a 1D array