sync: Make BaseNode lookup-related Init functions return specific failures.

chrome/browser/sync/internal_api/base_node.h

 // 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.
 
 #ifndef CHROME_BROWSER_SYNC_INTERNAL_API_BASE_NODE_H_
 #define CHROME_BROWSER_SYNC_INTERNAL_API_BASE_NODE_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 38 matching lines @@
 // A valid BaseNode will never have an ID of zero.
 static const int64 kInvalidId = 0;
 
 // BaseNode wraps syncable::Entry, and corresponds to a single object's state.
 // This, like syncable::Entry, is intended for use on the stack.  A valid
 // transaction is necessary to create a BaseNode or any of its children.
 // Unlike syncable::Entry, a sync API BaseNode is identified primarily by its
 // int64 metahandle, which we call an ID here.
 class BaseNode {
  public:
+  // Enumerates the possible outcomes of trying to initialize a sync node.
+  enum InitByLookupResult {
+    INIT_OK,
+    // Could not find an entry matching the lookup criteria.
+    INIT_FAILED_ENTRY_NOT_GOOD,
+    // Found an entry, but it is already deleted.
+    INIT_FAILED_ENTRY_IS_DEL,
+    // Found an entry, but was unable to decrypt.
+    INIT_FAILED_DECRYPT_IF_NECESSARY,
+    // A precondition was not met for calling init, such as legal input
+    // arguments.
+    INIT_FAILED_PRECONDITION,
+  };
+
   // All subclasses of BaseNode must provide a way to initialize themselves by
   // doing an ID lookup.  Returns false on failure.  An invalid or deleted
   // ID will result in failure.
-  virtual bool InitByIdLookup(int64 id) = 0;
+  virtual InitByLookupResult InitByIdLookup(int64 id) = 0;
 
   // All subclasses of BaseNode must also provide a way to initialize themselves
   // by doing a client tag lookup. Returns false on failure. A deleted node
   // will return FALSE.
-  virtual bool InitByClientTagLookup(syncable::ModelType model_type,
+  virtual InitByLookupResult InitByClientTagLookup(
+      syncable::ModelType model_type,
       const std::string& tag) = 0;
 
   // Each object is identified by a 64-bit id (internally, the syncable
   // metahandle).  These ids are strictly local handles.  They will persist
   // on this client, but the same object on a different client may have a
   // different ID value.
   virtual int64 GetId() const;
 
   // Returns the modification time of the object.
   const base::Time& GetModificationTime() const;
@@ skipping 153 matching lines @@
 
   // Same as |unencrypted_data_|, but for legacy password encryption.
   scoped_ptr<sync_pb::PasswordSpecificsData> password_data_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseNode);
 };
 
 }  // namespace sync_api
 
 #endif  // CHROME_BROWSER_SYNC_INTERNAL_API_BASE_NODE_H_