Add python test for deprecated syntax

PiperOrigin-RevId: 563175424

python/google/protobuf/internal/descriptor_test.py

@@ -553,6 +553,7 @@ class DescriptorTest(unittest.TestCase):
     self.assertEqual(self.my_file.package, 'protobuf_unittest')
     self.assertEqual(self.my_file.pool, self.pool)
     self.assertFalse(self.my_file.has_options)
+    self.assertEqual(self.my_file.syntax, 'proto2')
     file_proto = descriptor_pb2.FileDescriptorProto()
     self.my_file.CopyToProto(file_proto)
     self.assertEqual(self.my_file.serialized_pb,

upb/python/descriptor.c

@@ -639,7 +639,13 @@ static PyGetSetDef PyUpb_Descriptor_Getters[] = {
      "Containing type"},
     {"is_extendable", PyUpb_Descriptor_GetIsExtendable, NULL},
     {"has_options", PyUpb_Descriptor_GetHasOptions, NULL, "Has Options"},
+    // begin:github_only
     {"syntax", &PyUpb_Descriptor_GetSyntax, NULL, "Syntax"},
+    // end:github_only
+    // begin:google_only
+//     // TODO(b/271287872) Use this to open-source syntax deprecation.
+//     {"deprecated_syntax", &PyUpb_Descriptor_GetSyntax, NULL, "Syntax"},
+    // end:google_only
     {NULL}};
 
 static PyMethodDef PyUpb_Descriptor_Methods[] = {
@@ -1328,7 +1334,14 @@ static PyGetSetDef PyUpb_FileDescriptor_Getters[] = {
     {"public_dependencies", PyUpb_FileDescriptor_GetPublicDependencies, NULL,
      "Dependencies"},
     {"has_options", PyUpb_FileDescriptor_GetHasOptions, NULL, "Has Options"},
+    // begin:github_only
     {"syntax", PyUpb_FileDescriptor_GetSyntax, (setter)NULL, "Syntax"},
+    // end:github_only
+    // begin:google_only
+//     // TODO(b/271287872) Use this to open-source syntax deprecation.
+//     {"deprecated_syntax", PyUpb_FileDescriptor_GetSyntax, (setter)NULL,
+//      "Syntax"},
+    // end:google_only
     {NULL},
 };