Avoid collision name problems between a message named Xyz and a direct sibling enum named XyzView

We unfortuantely have no holistic startegy to avoid broken gencode from cross-type name collisions. We hold a high bar for special case mangling cross-type collisions, but this specific naming pattern combination is recommended by AIP 157.

Note that we will still break if the Xyz message and the XyzView enum are defined in separate .proto files but built in the same crate. It is very difficult for us to avoid that specific collision, so we are punting on it for now and only handling the case where the message and enum are defined in the same file. Especially when using blazel, we recommend one proto_library() per proto file, which would avoid that topic from being a concern.

PiperOrigin-RevId: 853935768

Author: protobuf-github-bot

rust/test/bad_names.proto

@@ -56,3 +56,8 @@ message AccessorsCollide {
 
   optional int32 clear_x = 7;
 }
+
+message SomeMsg {}
+enum SomeMsgView {
+  SOME_MSG_VIEW_UNSPECIFIED = 0;
+}

src/google/protobuf/compiler/rust/naming.cc

@@ -310,8 +310,52 @@ std::string RsSafeName(absl::string_view name) {
   return std::string(name);
 }
 
+namespace {
+
+bool AnyChildMessageNamed(const FileDescriptor* scope, absl::string_view name) {
+  for (int i = 0; i < scope->message_type_count(); ++i) {
+    if (scope->message_type(i)->name() == name) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool AnyChildMessageNamed(const Descriptor* scope, absl::string_view name) {
+  for (int i = 0; i < scope->nested_type_count(); ++i) {
+    if (scope->nested_type(i)->name() == name) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool MustMangleEnumName(const EnumDescriptor& desc) {
+  // If an enum name ends with 'View', we check if there is a message whose name
+  // matches the enum name without the 'View' suffix. If so,
+  // append an extra 'X' character on the end of the gencode enum name. The
+  // reason we special case mangle this is to avoid breakages from the View
+  // type of the message when the .proto file is following this AIP:
+  // https://google.aip.dev/157#view-enumeration
+  if (!absl::EndsWith(desc.name(), "View")) {
+    return false;
+  }
+  absl::string_view name_without_view_suffix =
+      absl::StripSuffix(desc.name(), "View");
+  return desc.containing_type() != nullptr
+             ? AnyChildMessageNamed(desc.containing_type(),
+                                    name_without_view_suffix)
+             : AnyChildMessageNamed(desc.file(), name_without_view_suffix);
+}
+
+}  // namespace
+
 std::string EnumRsName(const EnumDescriptor& desc) {
-  return RsSafeName(SnakeToUpperCamelCase(desc.name()));
+  std::string name = RsSafeName(SnakeToUpperCamelCase(desc.name()));
+  if (MustMangleEnumName(desc)) {
+    absl::StrAppend(&name, "_");
+  }
+  return name;
 }
 
 std::string EnumValueRsName(const EnumValueDescriptor& value) {
@@ -323,7 +367,8 @@ std::string EnumValueRsName(const MultiCasePrefixStripper& stripper,
                             absl::string_view value_name) {
   // Enum values may have a prefix of the name of the enum stripped from the
   // value names in the gencode. This prefix is flexible:
-  // - It can be the original enum name, the name as UpperCamel, or snake_case.
+  // - It can be the original enum name, the name as UpperCamel, or
+  // snake_case.
   // - The stripped prefix may also end in an underscore.
   auto stripped = stripper.StripPrefix(value_name);