Change the error handling location from DataLoader to Engine.

* Engine::MaybeReloadEngine takes care of all error handing of DataLoader::Response.
* This is a preparation CL for the next CL (cl/615733907).

#codehealth

PiperOrigin-RevId: 617099369

src/engine/BUILD.bazel

@@ -45,7 +45,6 @@ mozc_cc_library(
         "//base:file_util",
         "//base:hash",
         "//base:thread",
-        "//base/protobuf:message",
         "//data_manager",
         "//protocol:engine_builder_cc_proto",
         "@com_google_absl//absl/base:core_headers",
@@ -172,6 +171,7 @@ mozc_cc_library(
         ":spellchecker_interface",
         ":user_data_manager_interface",
         "//base:vlog",
+        "//base/protobuf:message",
         "//converter",
         "//converter:converter_interface",
         "//converter:immutable_converter_interface",

src/engine/data_loader.cc

@@ -40,7 +40,6 @@
 #include "absl/synchronization/mutex.h"
 #include "base/file_util.h"
 #include "base/hash.h"
-#include "base/protobuf/message.h"
 #include "base/thread.h"
 #include "data_manager/data_manager.h"
 #include "engine/modules.h"
@@ -227,16 +226,6 @@ DataLoader::MaybeMoveDataLoaderResponse() {
       std::move(*loader_response_future_).Get();
   loader_response_future_.reset();
 
-  if (!loader_response.modules ||
-      loader_response.response.status() != EngineReloadResponse::RELOAD_READY) {
-    // The loader_response does not contain a valid result.
-
-    // This engine id causes a critical error, so rollback the id.
-    LOG(ERROR) << "Failure in engine loading: "
-               << protobuf::Utf8Format(loader_response.response);
-    ReportLoadFailure(loader_response.id);
-    return nullptr;
-  }
   return std::make_unique<DataLoader::Response>(std::move(loader_response));
 }
 

src/engine/engine.cc

@@ -38,6 +38,7 @@
 #include "absl/status/status.h"
 #include "absl/status/statusor.h"
 #include "absl/strings/string_view.h"
+#include "base/protobuf/message.h"
 #include "base/vlog.h"
 #include "converter/converter.h"
 #include "converter/immutable_converter.h"
@@ -281,13 +282,24 @@ bool Engine::MaybeReloadEngine(EngineReloadResponse *response) {
   }
   *response = loader_response->response;
 
+  if (!loader_response->modules ||
+      response->status() != EngineReloadResponse::RELOAD_READY) {
+    // The loader_response does not contain a valid result.
+
+    // This request id causes a critical error, so rollback the id.
+    LOG(ERROR) << "Failure in loading response: "
+               << protobuf::Utf8Format(*response);
+    loader_->ReportLoadFailure(loader_response->id);
+    return false;
+  }
+
   if (user_data_manager_) {
     user_data_manager_->Wait();
   }
 
   // Reloads DataManager.
-  const bool is_mobile = loader_response->response.request().engine_type() ==
-                         EngineReloadRequest::MOBILE;
+  const bool is_mobile =
+      response->request().engine_type() == EngineReloadRequest::MOBILE;
   absl::Status reload_status =
       ReloadModules(std::move(loader_response->modules), is_mobile);
   if (!reload_status.ok()) {