Fixed the use of c++ keywords within namespace names (#15954)

Closes #15954

COPYBARA_INTEGRATE_REVIEW=https://github.com/protocolbuffers/protobuf/pull/15954 from Ilukatsk:main acf3fa436c
PiperOrigin-RevId: 611573919

src/google/protobuf/compiler/cpp/helpers.cc

@@ -28,7 +28,9 @@
 #include "absl/strings/ascii.h"
 #include "absl/strings/escaping.h"
 #include "absl/strings/str_cat.h"
+#include "absl/strings/str_join.h"
 #include "absl/strings/str_replace.h"
+#include "absl/strings/str_split.h"
 #include "absl/strings/string_view.h"
 #include "absl/strings/substitute.h"
 #include "absl/synchronization/mutex.h"
@@ -55,10 +57,6 @@ namespace {
 constexpr absl::string_view kAnyMessageName = "Any";
 constexpr absl::string_view kAnyProtoFile = "google/protobuf/any.proto";
 
-std::string DotsToColons(absl::string_view name) {
-  return absl::StrReplaceAll(name, {{".", "::"}});
-}
-
 static const char* const kKeywordList[] = {
     // clang-format off
     "NULL",
@@ -427,6 +425,21 @@ std::string QualifiedExtensionName(const FieldDescriptor* d) {
   return QualifiedExtensionName(d, Options());
 }
 
+std::string ResolveKeyword(absl::string_view name) {
+  if (Keywords().count(name) > 0) {
+    return absl::StrCat(name, "_");
+  }
+  return std::string(name);
+}
+
+std::string DotsToColons(absl::string_view name) {
+  std::vector<std::string> scope = absl::StrSplit(name, ".", absl::SkipEmpty());
+  for (auto& word : scope) {
+    word = ResolveKeyword(word);
+  }
+  return absl::StrJoin(scope, "::");
+}
+
 std::string Namespace(absl::string_view package) {
   if (package.empty()) return "";
   return absl::StrCat("::", DotsToColons(package));
@@ -504,13 +517,6 @@ std::string SuperClassName(const Descriptor* descriptor,
                       "::internal::", simple_base);
 }
 
-std::string ResolveKeyword(absl::string_view name) {
-  if (Keywords().count(name) > 0) {
-    return absl::StrCat(name, "_");
-  }
-  return std::string(name);
-}
-
 std::string FieldName(const FieldDescriptor* field) {
   std::string result = field->name();
   absl::AsciiStrToLower(&result);