fix(types): Buffer type hint (#5662)

* Fix Buffer type hint

collections.abc.Buffer was added in Python 3.12.
The previous behaviour should be used prior to this version.

* Fix comment

* Fix indentation

* style: pre-commit fixes

* Fix test

* Add missing import

* style: pre-commit fixes

---------

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

Author: gentlegiantJGC

include/pybind11/cast.h

@@ -1387,7 +1387,7 @@ struct handle_type_name<bytes> {
 };
 template <>
 struct handle_type_name<buffer> {
-    static constexpr auto name = const_name("collections.abc.Buffer");
+    static constexpr auto name = const_name(PYBIND11_BUFFER_TYPE_HINT);
 };
 template <>
 struct handle_type_name<int_> {

include/pybind11/detail/common.h

@@ -239,6 +239,13 @@
 #    define PYBIND11_SUBINTERPRETER_SUPPORT
 #endif
 
+// 3.12 Compatibility
+#if 0x030C0000 <= PY_VERSION_HEX
+#    define PYBIND11_BUFFER_TYPE_HINT "collections.abc.Buffer"
+#else
+#    define PYBIND11_BUFFER_TYPE_HINT "typing_extensions.Buffer"
+#endif
+
 // #define PYBIND11_STR_LEGACY_PERMISSIVE
 // If DEFINED, pybind11::str can hold PyUnicodeObject or PyBytesObject
 //             (probably surprising and never documented, but this was the

tests/test_buffers.py

@@ -3,6 +3,7 @@
 import ctypes
 import io
 import struct
+import sys
 
 import pytest
 
@@ -228,10 +229,11 @@ def test_ctypes_from_buffer():
 
 
 def test_buffer_docstring():
-    assert (
-        m.get_buffer_info.__doc__.strip()
-        == "get_buffer_info(arg0: collections.abc.Buffer) -> pybind11_tests.buffers.buffer_info"
-    )
+    if sys.version_info >= (3, 12):
+        docstring = "get_buffer_info(arg0: collections.abc.Buffer) -> pybind11_tests.buffers.buffer_info"
+    else:
+        docstring = "get_buffer_info(arg0: typing_extensions.Buffer) -> pybind11_tests.buffers.buffer_info"
+    assert m.get_buffer_info.__doc__.strip() == docstring
 
 
 def test_buffer_exception():