Keep track of which attachments are referenced by which sync entries.

sync/api/sync_data.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sync/api/sync_data.h"
 
 #include <ostream>
 
 #include "base/json/json_writer.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 18 matching lines @@
 
 sync_pb::AttachmentIdProto IdToProto(
     const syncer::AttachmentId& attachment_id) {
   return attachment_id.GetProto();
 }
 
 syncer::AttachmentId ProtoToId(const sync_pb::AttachmentIdProto& proto) {
   return syncer::AttachmentId::CreateFromProto(proto);
 }
 
+// Return true iff |attachments| contains one or more elements with the same
+// AttachmentId.
+bool ContainsDuplicateAttachments(const syncer::AttachmentList& attachments) {
+  std::set<syncer::AttachmentId> id_set;
+  AttachmentList::const_iterator iter = attachments.begin();
+  AttachmentList::const_iterator end = attachments.end();
+  for (; iter != end; ++iter) {
+    if (id_set.find(iter->GetId()) != id_set.end()) {
+      return true;
+    }
+    id_set.insert(iter->GetId());
+  }
+  return false;
+}
+
 }  // namespace
 
 namespace syncer {
 
 void SyncData::ImmutableSyncEntityTraits::InitializeWrapper(Wrapper* wrapper) {
   *wrapper = new sync_pb::SyncEntity();
 }
 
 void SyncData::ImmutableSyncEntityTraits::DestroyWrapper(Wrapper* wrapper) {
   delete *wrapper;
@@ skipping 40 matching lines @@
 
 // Static.
 SyncData SyncData::CreateLocalData(const std::string& sync_tag,
                                    const std::string& non_unique_title,
                                    const sync_pb::EntitySpecifics& specifics) {
   syncer::AttachmentList attachments;
   return CreateLocalDataWithAttachments(
       sync_tag, non_unique_title, specifics, attachments);
 }
 
-// TODO(maniscalco): What should happen if the same Attachment appears in the
-// list twice? Document the behavior and add a test case.
-//
 // Static.
 SyncData SyncData::CreateLocalDataWithAttachments(
     const std::string& sync_tag,
     const std::string& non_unique_title,
     const sync_pb::EntitySpecifics& specifics,
     const AttachmentList& attachments) {
+  DCHECK(!ContainsDuplicateAttachments(attachments));
   sync_pb::SyncEntity entity;
   entity.set_client_defined_unique_tag(sync_tag);
   entity.set_non_unique_name(non_unique_title);
   entity.mutable_specifics()->CopyFrom(specifics);
   std::transform(attachments.begin(),
                  attachments.end(),
                  RepeatedFieldBackInserter(entity.mutable_attachment_id()),
                  AttachmentToProto);
-  // TODO(maniscalco): Actually pass the attachments to the ctor and make them
-  // available to the AttachmentService once this SyncData gets passed into
-  // GenericChangeProcesso::ProcessSyncChanges (bug 354530).
   AttachmentList copy_of_attachments(attachments);
   return SyncData(kInvalidId,
                   &entity,
                   &copy_of_attachments,
                   base::Time(),
                   AttachmentServiceProxy());
 }
 
 // Static.
 SyncData SyncData::CreateRemoteData(
@@ skipping 105 matching lines @@
   attachment_service_.GetOrDownloadAttachments(attachment_ids, callback);
 }
 
 void SyncDataRemote::DropAttachments(
     const AttachmentIdList& attachment_ids,
     const AttachmentService::DropCallback& callback) {
   attachment_service_.DropAttachments(attachment_ids, callback);
 }
 
 }  // namespace syncer