Fix metadata-only updates for Sugar v2 API

path='' means the caller wants to update only the metadata and "inherit" the
data from the previous version.

1 files changed, 12 insertions, 9 deletions

diff --git a/gdatastore/datastore.py b/gdatastore/datastore.py
index 3b77828..e85cc4f 100644
--- a/gdatastore/datastore.py
+++ b/gdatastore/datastore.py
@@ -268,7 +268,7 @@ class DBusApiSugarV2(dbus.service.Object):
 
         parent = latest_versions[0]
         object_id = parent['tree_id'], parent['version_id']
-        if self._compare_checksums(parent, file_path):
+        if self._check_identical(parent, file_path):
             self._internal_api.change_metadata(object_id, props)
             return success_cb(uid, None)
 
@@ -366,19 +366,22 @@ class DBusApiSugarV2(dbus.service.Object):
         return self._internal_api.find({'tree_id': uid},
             {'limit': 1, 'order_by': ['+timestamp']})[0]
 
-    def _compare_checksums(self, parent, child_data_path):
+    def _check_identical(self, parent, child_data_path):
+        """Check whether the new version contains the same data as the parent
+
+        If child_data_path is empty, but the parent contains data, that's
+        interpreted as wanting to do a metadata-only update (emulating
+        sugar-datastore behaviour).
+        """
         parent_object_id = (parent['tree_id'], parent['version_id'])
         parent_data_path = self._internal_api.get_data_path(parent_object_id)
-        if bool(child_data_path) ^ bool(parent_data_path):
-            return False
-        elif not child_data_path:
+        if not child_data_path:
             return True
+        elif child_data_path and not parent_data_path:
+            return False
 
+        # TODO: compare checksums?
         return False
-        parent_checksum = self._internal_api.get_data_checksum(
-            parent_object_id)
-        child_checksum = calculate_checksum(child_data_path)
-        return parent_checksum == child_checksum
 
     def __change_metadata_cb(self, (tree_id, version_id), metadata):
         self.Updated(tree_id)