type_caster<absl::Cord>: return Python str when given `return_val…

…ue_policy::_clif_automatic`.

Compared to other string-kind `type_caster`s in pybind11, `type_caster<absl::Cord>` is unusual in that it returns `bytes`. All other string-kind `type_caster`s return `str` and can be directed to use `bytes` instead via `return_value_policy::_return_as_bytes`. There is no `return_value_policy::return_as_str` that we could use here. Introducing such a policy just for `type_caster<absl::Cord>` seems heavy-handed. The existing `return_value_policy::_clif_automatic` fits this niche case organically and is fully sufficient for the purposes of PyCLIF-pybind11.

PiperOrigin-RevId: 620916112

pybind11_abseil/absl_casters.h

@@ -627,8 +627,13 @@ struct type_caster<absl::Cord> {
   }
 
   // Conversion part 2 (C++ -> Python)
-  static handle cast(const absl::Cord& src, return_value_policy /*policy*/,
+  static handle cast(const absl::Cord& src, return_value_policy policy,
                      handle /*parent*/) {
+#if defined(PYBIND11_HAS_RETURN_VALUE_POLICY_CLIF_AUTOMATIC)
+    if (policy == return_value_policy::_clif_automatic) {
+      return str(std::string(src)).release();
+    }
+#endif
     return bytes(std::string(src)).release();
   }
 };

pybind11_abseil/requirements/BUILD

@@ -1,13 +1,13 @@
+load("@python//3.10:defs.bzl", compile_pip_requirements_3_10 = "compile_pip_requirements")
+load("@python//3.11:defs.bzl", compile_pip_requirements_3_11 = "compile_pip_requirements")
+load("@python//3.12:defs.bzl", compile_pip_requirements_3_12 = "compile_pip_requirements")
+load("@python//3.8:defs.bzl", compile_pip_requirements_3_8 = "compile_pip_requirements")
+load("@python//3.9:defs.bzl", compile_pip_requirements_3_9 = "compile_pip_requirements")
+
 package(
     default_visibility = ["//visibility:private"],
 )
 
-load("@python//3.12:defs.bzl", compile_pip_requirements_3_12 = "compile_pip_requirements")
-load("@python//3.11:defs.bzl", compile_pip_requirements_3_11 = "compile_pip_requirements")
-load("@python//3.10:defs.bzl", compile_pip_requirements_3_10 = "compile_pip_requirements")
-load("@python//3.9:defs.bzl", compile_pip_requirements_3_9 = "compile_pip_requirements")
-load("@python//3.8:defs.bzl", compile_pip_requirements_3_8 = "compile_pip_requirements")
-
 compile_pip_requirements_3_12(
     name = "requirements_3_12",
     src = "requirements.in",

pybind11_abseil/tests/absl_example.cc

@@ -363,6 +363,13 @@ static_assert(
     !std::is_const<const int*>::value);  // int is const, pointer is not.
 
 PYBIND11_MODULE(absl_example, m) {
+  m.attr("PYBIND11_HAS_RETURN_VALUE_POLICY_CLIF_AUTOMATIC") =
+#if defined(PYBIND11_HAS_RETURN_VALUE_POLICY_CLIF_AUTOMATIC)
+      true;
+#else
+      false;
+#endif
+
   // absl::Time/Duration bindings.
   m.def("make_duration", &MakeDuration, arg("secs"));
   m.def("make_infinite_duration", &MakeInfiniteDuration);
@@ -440,6 +447,11 @@ PYBIND11_MODULE(absl_example, m) {
   // absl::Cord bindings.
   m.def("check_absl_cord", &CheckAbslCord, arg("view"), arg("values"));
   m.def("return_absl_cord", &ReturnAbslCord, arg("values"));
+#if defined(PYBIND11_HAS_RETURN_VALUE_POLICY_CLIF_AUTOMATIC)
+  m.def("return_absl_cord_clif_automatic", [](const std::string& values) {
+    return cast(ReturnAbslCord(values), return_value_policy::_clif_automatic);
+  });
+#endif
 
   // absl::optional bindings.
   m.def("check_optional", &CheckOptional, arg("optional") = absl::nullopt,

pybind11_abseil/tests/absl_test.py

@@ -487,12 +487,24 @@ class AbslCordTest(absltest.TestCase):
   TEST_STRING = 'absl_Cord'
   TEST_BYTES = b'absl_Cord'
 
-  def test_return_absl_cord(self):
+  def test_return_absl_cord_rvp_not_specified(self):
     self.assertSequenceEqual(
         absl_example.return_absl_cord(self.TEST_STRING), self.TEST_BYTES)
     self.assertSequenceEqual(
         absl_example.return_absl_cord(self.TEST_BYTES), self.TEST_BYTES)
 
+  def test_return_absl_cord_rvp_clif_automatic(self):
+    if not absl_example.PYBIND11_HAS_RETURN_VALUE_POLICY_CLIF_AUTOMATIC:
+      self.skipTest('return_value_policy::_clif_automatic not available')
+    self.assertSequenceEqual(
+        absl_example.return_absl_cord_clif_automatic(self.TEST_STRING),
+        self.TEST_STRING,
+    )
+    self.assertSequenceEqual(
+        absl_example.return_absl_cord_clif_automatic(self.TEST_BYTES),
+        self.TEST_STRING,
+    )
+
   def test_pass_absl_cord(self):
     self.assertTrue(
         absl_example.check_absl_cord(self.TEST_STRING, self.TEST_STRING))