PYBIND11_OBJECT_CVT should use namespace for error_already_set() (pybind#3797)

* PYBIND11_OBJECT_CVT should use namespace for error_already_set()

This change makes the macro usable outside of pybind11 namespace.

* added test for use of PYBIND11_OBJECT_CVT for classes in external to pybind11 namespaces

* Extended test_pytypes.cpp and test_pytest.py

The added test defines a dummy function that takes a custom-defined class external::float_
that uses PYBIND11_OBJECT_CVT

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* fixed issues pointed out by CI

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fixed memory leak in default constructor

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

Author: 2 people

include/pybind11/pytypes.h

@@ -1053,12 +1053,12 @@ public:
     Name(const object &o)                                                                         \
         : Parent(check_(o) ? o.inc_ref().ptr() : ConvertFun(o.ptr()), stolen_t{}) {               \
         if (!m_ptr)                                                                               \
-            throw error_already_set();                                                            \
+            throw ::pybind11::error_already_set();                                                \
     }                                                                                             \
     /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
     Name(object &&o) : Parent(check_(o) ? o.release().ptr() : ConvertFun(o.ptr()), stolen_t{}) {  \
         if (!m_ptr)                                                                               \
-            throw error_already_set();                                                            \
+            throw ::pybind11::error_already_set();                                                \
     }
 
 #define PYBIND11_OBJECT_CVT_DEFAULT(Name, Parent, CheckFun, ConvertFun)                           \

tests/test_pytypes.cpp

@@ -11,6 +11,34 @@
 
 #include <utility>
 
+namespace external {
+namespace detail {
+bool check(PyObject *o) { return PyFloat_Check(o) != 0; }
+
+PyObject *conv(PyObject *o) {
+    PyObject *ret = nullptr;
+    if (PyLong_Check(o)) {
+        double v = PyLong_AsDouble(o);
+        if (!(v == -1.0 && PyErr_Occurred())) {
+            ret = PyFloat_FromDouble(v);
+        }
+    } else {
+        PyErr_SetString(PyExc_TypeError, "Unexpected type");
+    }
+    return ret;
+}
+
+PyObject *default_constructed() { return PyFloat_FromDouble(0.0); }
+} // namespace detail
+class float_ : public py::object {
+    PYBIND11_OBJECT_CVT(float_, py::object, external::detail::check, external::detail::conv)
+
+    float_() : py::object(external::detail::default_constructed(), stolen_t{}) {}
+
+    double get_value() const { return PyFloat_AsDouble(this->ptr()); }
+};
+} // namespace external
+
 TEST_SUBMODULE(pytypes, m) {
     // test_bool
     m.def("get_bool", [] { return py::bool_(false); });
@@ -549,4 +577,9 @@ TEST_SUBMODULE(pytypes, m) {
         py::detail::accessor_policies::tuple_item::set(o, (py::size_t) 0, s0);
         return o;
     });
+
+    m.def("square_float_", [](const external::float_ &x) -> double {
+        double v = x.get_value();
+        return v * v;
+    });
 }

tests/test_pytypes.py

@@ -657,3 +657,8 @@ def test_implementation_details():
     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")
+
+
+def test_external_float_():
+    r1 = m.square_float_(2.0)
+    assert r1 == 4.0