SymbolChecker: Bugfix to take parent message visibility into account.

The early exit in IsNamespacedEnum would trigger examples like

edition = "2024";

local message Parent {
  export enum Child {
     ZERO = 0;
  }
  reserved 1 to max;
}

to be considered not namespaced, as the default-to-local early exit would fire.

New unit tests are added for this and related cases.

PiperOrigin-RevId: 871320466

Author: pizzud

src/google/protobuf/symbol_checker.cc

@@ -132,7 +132,7 @@ bool SymbolChecker::IsEnumNamespaceMessage(const Descriptor& container) {
 }
 
 bool SymbolChecker::IsNamespacedEnum(const EnumDescriptor& enm) {
-  // Only allowed for top-level messages
+  // If the enum is top-level, it definitely isn't namespaced.
   if (enm.containing_type() == nullptr) {
     return false;
   }
@@ -147,12 +147,10 @@ bool SymbolChecker::IsNamespacedEnum(const EnumDescriptor& enm) {
   // This check only cares if the enum is explicitly marked export, the
   // containing message can be local or unset with the file default making it
   // local.
-  if (!default_to_local ||
-      enm.visibility_keyword() != SymbolVisibility::VISIBILITY_EXPORT) {
-    return false;
-  }
-
-  return IsEnumNamespaceMessage(*enm.containing_type());
+  bool is_exported =
+      !default_to_local ||
+      enm.visibility_keyword() == SymbolVisibility::VISIBILITY_EXPORT;
+  return is_exported && IsEnumNamespaceMessage(*enm.containing_type());
 }
 
 void SymbolChecker::Initialize() {

src/google/protobuf/symbol_checker_test.cc

@@ -242,6 +242,69 @@ TEST_F(SymbolCheckerTest, IsEnumNamespaceMessage) {
   ASSERT_FALSE(SymbolChecker::IsNamespacedEnum(*top_enum_descriptor));
 }
 
+TEST_F(SymbolCheckerTest, IsNamespacedEnumLocalDefault) {
+  pool_.EnforceSymbolVisibility(true);
+  const FileDescriptor* file = ParseAndBuildFile("vis.proto", R"schema(
+        edition = "2024";
+        package vis.test;
+
+        option features.default_symbol_visibility = LOCAL_ALL;
+        message EnumNamespaceMessage {
+          export enum Enum {
+            FOO = 0;
+          }
+          reserved 1 to max;
+        }
+
+        enum TopLevelEnum {
+          BAR = 0;
+        }
+        )schema");
+
+  ASSERT_THAT(file, NotNull());
+
+  const Descriptor* namespace_message =
+      file->FindMessageTypeByName("EnumNamespaceMessage");
+  ASSERT_THAT(namespace_message, NotNull());
+
+  const EnumDescriptor* enum_descriptor =
+      namespace_message->FindEnumTypeByName("Enum");
+  ASSERT_THAT(enum_descriptor, NotNull());
+
+  ASSERT_TRUE(SymbolChecker::IsNamespacedEnum(*enum_descriptor));
+}
+
+TEST_F(SymbolCheckerTest, IsNamespacedEnumExplicitlyLocalParent) {
+  pool_.EnforceSymbolVisibility(true);
+  const FileDescriptor* file = ParseAndBuildFile("vis.proto", R"schema(
+        edition = "2024";
+        package vis.test;
+
+        local message EnumNamespaceMessage {
+          enum Enum {
+            FOO = 0;
+          }
+          reserved 1 to max;
+        }
+
+        enum TopLevelEnum {
+          BAR = 0;
+        }
+        )schema");
+
+  ASSERT_THAT(file, NotNull());
+
+  const Descriptor* namespace_message =
+      file->FindMessageTypeByName("EnumNamespaceMessage");
+  ASSERT_THAT(namespace_message, NotNull());
+
+  const EnumDescriptor* enum_descriptor =
+      namespace_message->FindEnumTypeByName("Enum");
+  ASSERT_THAT(enum_descriptor, NotNull());
+
+  ASSERT_TRUE(SymbolChecker::IsNamespacedEnum(*enum_descriptor));
+}
+
 TEST_F(SymbolCheckerTest, IsNotEnumNamespaceMessage) {
   pool_.EnforceSymbolVisibility(true);