Raise warnings for python syntax usages

PiperOrigin-RevId: 579344748

3 files changed, 43 insertions, 5 deletions

diff --git a/python/descriptor.c b/python/descriptor.c
index be1a839ac..023e94360 100644
--- a/python/descriptor.c
+++ b/python/descriptor.c
@@ -620,6 +620,11 @@ static PyObject* PyUpb_Descriptor_GetOneofsByName(PyObject* _self,
 }
 
 static PyObject* PyUpb_Descriptor_GetSyntax(PyObject* self, void* closure) {
+  PyErr_WarnEx(NULL,
+               "descriptor.syntax is deprecated. It will be removed soon. "
+               "Most usages are checking field descriptors. Consider to use "
+               "has_presence, is_packed on field descriptors.",
+               1);
   const upb_MessageDef* msgdef = PyUpb_Descriptor_GetDef(self);
   const char* syntax =
       upb_MessageDef_Syntax(msgdef) == kUpb_Syntax_Proto2 ? "proto2" : "proto3";
@@ -1309,6 +1314,11 @@ static PyObject* PyUpb_FileDescriptor_GetPublicDependencies(PyObject* _self,
 
 static PyObject* PyUpb_FileDescriptor_GetSyntax(PyObject* _self,
                                                 void* closure) {
+  PyErr_WarnEx(NULL,
+               "descriptor.syntax is deprecated. It will be removed soon. "
+               "Most usages are checking field descriptors. Consider to use "
+               "has_presence, is_packed on field descriptors.",
+               1);
   PyUpb_DescriptorBase* self = (void*)_self;
   const char* syntax =
       upb_FileDef_Syntax(self->def) == kUpb_Syntax_Proto2 ? "proto2" : "proto3";
diff --git a/python/google/protobuf/descriptor.py b/python/google/protobuf/descriptor.py
index f8b12ff13..5b32e5e15 100755
--- a/python/google/protobuf/descriptor.py
+++ b/python/google/protobuf/descriptor.py
@@ -353,10 +353,19 @@ class Descriptor(_NestedDescriptorBase):
     self.oneofs_by_name = dict((o.name, o) for o in self.oneofs)
     for oneof in self.oneofs:
       oneof.containing_type = self
-    self.syntax = syntax or "proto2"
+    self._deprecated_syntax = syntax or "proto2"
     self._is_map_entry = is_map_entry
 
   @property
+  def syntax(self):
+    warnings.warn(
+      'descriptor.syntax is deprecated. It will be removed'
+      ' soon. Most usages are checking field descriptors. Consider to use'
+      ' has_presence, is_packed on field descriptors.'
+    )
+    return self._deprecated_syntax
+
+  @property
   def fields_by_camelcase_name(self):
     """Same FieldDescriptor objects as in :attr:`fields`, but indexed by
     :attr:`FieldDescriptor.camelcase_name`.
@@ -621,7 +630,7 @@ class FieldDescriptor(DescriptorBase):
     # compatibility. FieldDescriptor.file was added in cl/153110619
     # Some old/generated code didn't link file to FieldDescriptor.
     # TODO: remove syntax usage b/240619313
-    return self.containing_type.syntax == 'proto2'
+    return self.containing_type._deprecated_syntax == 'proto2'
 
   @property
   def is_packed(self):
@@ -634,7 +643,7 @@ class FieldDescriptor(DescriptorBase):
         field_type == FieldDescriptor.TYPE_MESSAGE or
         field_type == FieldDescriptor.TYPE_BYTES):
       return False
-    if self.containing_type.syntax == 'proto2':
+    if self.containing_type._deprecated_syntax == 'proto2':
       return self.has_options and self.GetOptions().packed
     else:
       return (not self.has_options or
@@ -743,7 +752,7 @@ class EnumDescriptor(_NestedDescriptorBase):
     Care should be taken when using this function to respect the target
     runtime's enum handling quirks.
     """
-    return self.file.syntax == 'proto2'
+    return self.file._deprecated_syntax == 'proto2'
 
   def CopyToProto(self, proto):
     """Copies this to a descriptor_pb2.EnumDescriptorProto.
@@ -1083,7 +1092,7 @@ class FileDescriptor(DescriptorBase):
     self.message_types_by_name = {}
     self.name = name
     self.package = package
-    self.syntax = syntax or "proto2"
+    self._deprecated_syntax = syntax or "proto2"
     self.serialized_pb = serialized_pb
 
     self.enum_types_by_name = {}
@@ -1092,6 +1101,15 @@ class FileDescriptor(DescriptorBase):
     self.dependencies = (dependencies or [])
     self.public_dependencies = (public_dependencies or [])
 
+  @property
+  def syntax(self):
+    warnings.warn(
+      'descriptor.syntax is deprecated. It will be removed'
+      ' soon. Most usages are checking field descriptors. Consider to use'
+      ' has_presence, is_packed on field descriptors.'
+    )
+    return self._deprecated_syntax
+
   def CopyToProto(self, proto):
     """Copies this to a descriptor_pb2.FileDescriptorProto.
 
diff --git a/python/google/protobuf/pyext/descriptor.cc b/python/google/protobuf/pyext/descriptor.cc
index 44d9e4517..734aea66a 100644
--- a/python/google/protobuf/pyext/descriptor.cc
+++ b/python/google/protobuf/pyext/descriptor.cc
@@ -672,6 +672,11 @@ static PyObject* EnumValueName(PyBaseDescriptor *self, PyObject *args) {
 }
 
 static PyObject* GetSyntax(PyBaseDescriptor *self, void *closure) {
+  PyErr_WarnEx(nullptr,
+               "descriptor.syntax is deprecated. It will be removed soon. "
+               "Most usages are checking field descriptors. Consider to use "
+               "has_presence, is_packed on field descriptors.",
+               1);
   std::string syntax(FileDescriptorLegacy::SyntaxName(
       FileDescriptorLegacy(_GetDescriptor(self)->file()).syntax()));
   return PyUnicode_InternFromString(syntax.c_str());
@@ -1493,6 +1498,11 @@ static int SetSerializedOptions(PyFileDescriptor *self, PyObject *value,
 }
 
 static PyObject* GetSyntax(PyFileDescriptor *self, void *closure) {
+  PyErr_WarnEx(nullptr,
+               "descriptor.syntax is deprecated. It will be removed soon. "
+               "Most usages are checking field descriptors. Consider to use "
+               "has_presence, is_packed on field descriptors.",
+               1);
   std::string syntax(FileDescriptorLegacy::SyntaxName(
       FileDescriptorLegacy(_GetDescriptor(self)).syntax()));
   return PyUnicode_InternFromString(syntax.c_str());