Add `absl::Span` `PyObject*` support in absl_casters.h.

PiperOrigin-RevId: 532586991

pybind11_abseil/absl_casters.h

@@ -33,6 +33,7 @@
 #include <pybind11/cast.h>
 #include <pybind11/pybind11.h>
 #include <pybind11/stl.h>
+#include <pybind11/type_caster_pyobject_ptr.h>
 
 // Must NOT appear before at least one pybind11 include.
 #include <datetime.h>  // Python datetime builtin.
@@ -392,11 +393,24 @@ namespace internal {
 
 template <typename T>
 static constexpr bool is_buffer_interface_compatible_type =
+    detail::is_same_ignoring_cvref<T, PyObject*>::value ||
     std::is_arithmetic<T>::value ||
     std::is_same<T, std::complex<float>>::value ||
     std::is_same<T, std::complex<double>>::value;
 
 template <typename T, typename SFINAE = void>
+struct format_descriptor_char1 : format_descriptor<T> {};
+
+template <typename T>
+struct format_descriptor_char1<
+    T,
+    detail::enable_if_t<detail::is_same_ignoring_cvref<T, PyObject*>::value>> {
+  static constexpr const char c = 'O';
+  static constexpr const char value[2] = {c, '\0'};
+  static std::string format() { return std::string(1, c); }
+};
+
+template <typename T, typename SFINAE = void>
 struct format_descriptor_char2 {
   static constexpr const char c = '\0';
 };
@@ -406,7 +420,7 @@ struct format_descriptor_char2<std::complex<T>> : format_descriptor<T> {};
 
 template <typename T>
 inline bool buffer_view_matches_format_descriptor(const char* view_format) {
-  return view_format[0] == format_descriptor<T>::c ||
+  return view_format[0] == format_descriptor_char1<T>::c ||
          (view_format[0] == 'Z' &&
           view_format[1] == format_descriptor_char2<T>::c);
 }

pybind11_abseil/tests/absl_example.cc

@@ -273,6 +273,12 @@ NonConstCmplxType SumSpanComplex(absl::Span<CmplxType> input_span) {
   return sum;
 }
 
+std::string PassSpanPyObjectPtr(absl::Span<PyObject*> input_span) {
+  std::string result;
+  for (auto& i : input_span) result += str(i);
+  return result;
+}
+
 struct ObjectForSpan {
   explicit ObjectForSpan(int v) : value(v) {}
   int value;
@@ -397,6 +403,7 @@ PYBIND11_MODULE(absl_example, m) {
   m.def("sum_span_complex128", &SumSpanComplex<std::complex<double>>);
   m.def("sum_span_const_complex128",
         &SumSpanComplex<const std::complex<double>>, arg("input_span"));
+  m.def("pass_span_pyobject_ptr", &PassSpanPyObjectPtr, arg("span"));
 
   // Span of objects.
   class_<ObjectForSpan>(m, "ObjectForSpan")

pybind11_abseil/tests/absl_test.py

@@ -378,6 +378,10 @@ class AbslNumericSpanTest(parameterized.TestCase):
     xs = np.array([x * 1j for x in range(10)]).astype(numpy_type)
     self.assertEqual(sum_span_fn(xs), 45j)
 
+  def test_pass_span_pyobject_ptr(self):
+    arr = np.array([-3, 'four', 5.0], dtype=object)
+    self.assertEqual(absl_example.pass_span_pyobject_ptr(arr), '-3four5.0')
+
 
 def make_native_list_of_objects():
   return [absl_example.ObjectForSpan(3), absl_example.ObjectForSpan(5)]