[ObjC] Put all enums into one file in multi file mode.

Since dead stripping is completely safe with C symbols and enums only generate C
functions, stick them all in one file to slightly reduce the potential cost of
multi file generation.

PiperOrigin-RevId: 503484196

src/google/protobuf/compiler/objectivec/file.cc

@@ -449,9 +449,12 @@ void FileGenerator::GenerateGlobalSource(io::Printer* p) const {
       });
 }
 
-void FileGenerator::GenerateSourceForEnum(int idx, io::Printer* p) const {
-  GenerateFile(p, GeneratedFileType::kSource,
-               [&] { enum_generators_[idx]->GenerateSource(p); });
+void FileGenerator::GenerateSourceForEnums(io::Printer* p) const {
+  GenerateFile(p, GeneratedFileType::kSource, [&] {
+    for (const auto& generator : enum_generators_) {
+      generator->GenerateSource(p);
+    }
+  });
 }
 
 void FileGenerator::GenerateSourceForMessage(int idx, io::Printer* p) const {

src/google/protobuf/compiler/objectivec/file.h

@@ -89,15 +89,16 @@ class FileGenerator {
 
   void GenerateGlobalSource(io::Printer* p) const;
   void GenerateSourceForMessage(int idx, io::Printer* p) const;
-  void GenerateSourceForEnum(int idx, io::Printer* p) const;
+  void GenerateSourceForEnums(io::Printer* p) const;
 
  private:
   enum class GeneratedFileType : int { kHeader, kSource };
 
-  void GenerateFile(io::Printer* p, GeneratedFileType file_type,
-                    const std::vector<std::string>& ignored_warnings,
-                    const std::vector<const FileDescriptor*>& extra_files,
-                    std::function<void()> body) const;
+  void GenerateFile(
+      io::Printer* p, GeneratedFileType file_type,
+      const std::vector<std::string>& ignored_warnings,
+      const std::vector<const FileDescriptor*>& extra_files_to_import,
+      std::function<void()> body) const;
   void GenerateFile(io::Printer* p, GeneratedFileType file_type,
                     std::function<void()> body) const {
     GenerateFile(p, file_type, {}, {}, body);

src/google/protobuf/compiler/objectivec/generator.cc

@@ -262,11 +262,10 @@ bool ObjectiveCGenerator::GenerateAll(
       // This is an experimental option, and could be removed or change at any
       // time; it is not documented in the README.md for that reason.
       //
-      // Enables a mode where each type (message & enum) generates to a unique
-      // .m file; this is to explore impacts on code size when not
+      // Enables a mode where each ObjC class (messages and roots) generates to
+      // a unique .m file; this is to explore impacts on code size when not
       // compiling/linking with `-ObjC` as then only linker visible needs should
       // be pulled into the builds.
-
       if (!StringToBool(
               options[i].second,
               &generation_options.experimental_multi_source_generation)) {
@@ -346,15 +345,17 @@ bool ObjectiveCGenerator::GenerateAll(
           }
         }
 
-        for (int i = 0; i < file_generator.NumEnums(); ++i) {
+        // Enums only generate C functions, so they can all go in one file as
+        // dead stripping anything not used.
+        if (file_generator.NumEnums() > 0) {
           std::unique_ptr<io::ZeroCopyOutputStream> output(
               context->Open(NumberedObjCMFileName(filepath, file_number++)));
           io::Printer printer(output.get());
-          file_generator.GenerateSourceForEnum(i, &printer);
+          file_generator.GenerateSourceForEnums(&printer);
           if (printer.failed()) {
             *error = absl::StrCat(
-                "error: internal error generating an enum implementation:",
-                file->name(), "::", i);
+                "error: internal error generating an enum implementation(s):",
+                file->name());
             return false;
           }
         }