From a5412936c72901026ecbdf0439cea77aaf922dad Mon Sep 17 00:00:00 2001
From: Protobuf Team Bot <protobuf-github-bot@google.com>
Date: Fri, 31 Jul 2026 16:13:43 -0700
Subject: [PATCH] Annotate extension names in hpb generator for Kythe metadata.

PiperOrigin-RevId: 957381097
---
 hpb_generator/gen_extensions.cc      |  5 ++++-
 hpb_generator/tests/metadata_test.cc | 29 ++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/hpb_generator/gen_extensions.cc b/hpb_generator/gen_extensions.cc
index 2938ef0408..2c7bea800d 100644
--- a/hpb_generator/gen_extensions.cc
+++ b/hpb_generator/gen_extensions.cc
@@ -22,6 +22,8 @@ namespace google {
 namespace protobuf {
 namespace hpb_generator {
 
+using Sub = google::protobuf::io::Printer::Sub;
+
 std::string ExtensionIdentifierBase(const google::protobuf::FieldDescriptor* ext) {
   assert(ext->is_extension());
   std::string ext_scope;
@@ -55,7 +57,8 @@ void WriteExtensionIdentifierHeader(const google::protobuf::FieldDescriptor* ext
        {"linkage", linkage},
        {"mini_table_name",
         absl::StrCat(ExtensionIdentifierBase(ext), "_", ext->name(), "_ext")},
-       {"extension_name", ResolveKeywordConflict(ext->name())},
+       Sub("extension_name", ResolveKeywordConflict(ext->name()))
+           .AnnotatedAs(ext),
        {"extension_number", ext->number()}},
       R"cc(
         inline $linkage$ constexpr ::hpb::internal::ExtensionIdentifier<
diff --git a/hpb_generator/tests/metadata_test.cc b/hpb_generator/tests/metadata_test.cc
index 502cb4985e..f8dc0ddd92 100644
--- a/hpb_generator/tests/metadata_test.cc
+++ b/hpb_generator/tests/metadata_test.cc
@@ -166,6 +166,35 @@ TEST_F(HpbMetadataTest, AnnotatesStringSemantics) {
                                   });
 }
 
+constexpr absl::string_view kExtensionTestFile = R"schema(
+    syntax = "proto2";
+    package foo;
+    message Message {
+      extensions 100 to 199;
+    }
+    extend Message {
+      optional string ext_field = 101;
+    }
+)schema";
+
+TEST_F(HpbMetadataTest, AnnotatesExtensionSemantics) {
+  FileDescriptorProto file;
+  GeneratedCodeInfo info;
+  std::string hpb_h;
+  atu::AddFile("test.proto", kExtensionTestFile);
+  EXPECT_TRUE(CaptureMetadata("test.proto", file, hpb_h, info));
+
+  // Check annotations for `ext_field`.
+  std::vector<int> field_path{
+      FileDescriptorProto::kExtensionFieldNumber,
+      0,
+  };
+  ExpectAnnotationsForPathContain(info, "test.proto", hpb_h, field_path,
+                                  {
+                                      {"ext_field", Annotation::NONE},
+                                  });
+}
+
 TEST_F(HpbMetadataTest, GeneratesMetadataPragma) {
   FileDescriptorProto file;
   GeneratedCodeInfo info;