Add Python deprecation warnings for Descriptor Label.

PiperOrigin-RevId: 756954086

Author: protobuf-github-bot

hpb/g3doc/index.md

@@ -0,0 +1,46 @@
+# Handle Protobuf - hbp
+
+go/hpb
+
+<!--*
+# Document freshness: For more information, see go/fresh-source.
+freshness: { owner: 'hongshin' reviewed: '2025-05-14' }
+*-->
+
+## What is hpb?
+
+hpb is a C++ Protobuf API that provides a familiar protobuf experience while
+hiding internal implementation details. This encapsulation allows for swapping
+out the backend without breaking user code. hpb wraps other protobuf
+implementations -- currently only upb is supported, but a proto2 C++ backend is
+in the early stages.
+
+hpb is designed to be a "free" wrapper, such that it adds no runtime overhead
+compared with using the underlying backend directly. The wrapping is all
+performed in header files that optimize away at compile time.
+
+hpb is the preferred solution for users who want to use upb protos in a C++
+application. Unlike the upb C generated code, hpb provides a stable API and
+properly handles naming conflicts. hpb is also far more ergonomic than the upb
+generated code.
+
+## Why hpb?
+
+-   As mentioned in go/upb, the upb C API is not stable, and not intended for
+    use in applications. hpb fills this gap.
+    -   upbc gencode can change and break clients at any time. hpb is designed
+        for user applications inside of g3 and has stronger guarantees of api
+        stability
+    -   LSCs/cleanups are handled by the Protobuf team - less maintenance burden
+-   Code will be more readable. Regular C++ method calls vs field accessors. No
+    need to provide fully qualified names in terra hpb.
+    -   `my_project_MyMessage_set_x` vs `msg.set_x()`
+-   [planned] Gives a transition path if your team wishes to move from proto2::cpp to upb
+    via hpb(cpp) -> hpb(upb). All toggled statically with a BUILD flag
+-   [planned] interop between hpb(upb) and hpb(cpp)
+
+## How can I get access?
+
+hpb is currently in special availability. If you think this would be a good
+fit for your team, please reach out to the Protobuf team.
+

hpb/g3doc/sitemap.md

@@ -0,0 +1,8 @@
+# hpb::
+
+<!--*
+# Document freshness: For more information, see go/fresh-source.
+freshness: { owner: 'hongshin' reviewed: '2025-05-14' }
+*-->
+
+*   [Home](/third_party/protobuf/hpb/g3doc/index.md)

python/descriptor.c

@@ -1054,8 +1054,20 @@ static PyObject* PyUpb_FieldDescriptor_GetCppType(PyUpb_DescriptorBase* self,
   return PyLong_FromLong(cpp_types[upb_FieldDef_CType(self->def)]);
 }
 
+static void WarnDeprecatedLabel(void) {
+  static int deprecated_label_count = 100;
+  if (deprecated_label_count > 0) {
+    --deprecated_label_count;
+    PyErr_WarnEx(
+        PyExc_DeprecationWarning,
+        "label() is deprecated. Use is_required() or is_repeated() instead.",
+        3);
+  }
+}
+
 static PyObject* PyUpb_FieldDescriptor_GetLabel(PyUpb_DescriptorBase* self,
                                                 void* closure) {
+  WarnDeprecatedLabel();
   return PyLong_FromLong(upb_FieldDef_Label(self->def));
 }