Don't modify data in library function.

- storage.save: Don't modify data. mopidy.__version__ has to be added by caller.
- storage.load: Added a Todo. Postponed decision, if load() shall raise an exception in case of error. See PR #310.

mopidy/core/actor.py

@@ -7,6 +7,8 @@ import os
 
 import pykka
 
+import mopidy
+
 from mopidy import audio, backend, mixer
 from mopidy.audio import PlaybackState
 from mopidy.core.history import HistoryController
@@ -188,6 +190,7 @@ class Core(
         logger.info('Save state to %s', file_name)
 
         data = {}
+        data['version'] = mopidy.__version__
         data['tracklist'] = self.tracklist._export_state()
         data['history'] = self.history._export_state()
         data['playback'] = self.playback._export_state()

mopidy/local/json.py

@@ -6,6 +6,8 @@ import os
 import re
 import sys
 
+import mopidy
+
 from mopidy import compat, local, models
 from mopidy.internal import timer
 from mopidy.local import search, storage, translator
@@ -164,7 +166,9 @@ class JsonLibrary(local.Library):
         self._tracks.pop(uri, None)
 
     def close(self):
-        models.storage.save(self._json_file, {'tracks': self._tracks.values()})
+        models.storage.save(self._json_file,
+                            {'version': mopidy.__version__,
+                             'tracks': self._tracks.values()})
 
     def clear(self):
         try:

mopidy/models/storage.py

@@ -6,7 +6,6 @@ import logging
 import os
 import tempfile
 
-import mopidy
 from mopidy import models
 from mopidy.internal import encoding
 
@@ -22,6 +21,7 @@ def load(path):
     :return: deserialized data
     :rtype: dict
     """
+    # Todo: raise an exception in case of error?
     if not os.path.isfile(path):
         logger.info('File does not exist: %s.', path)
         return {}
@@ -44,7 +44,6 @@ def save(path, data):
     :param data: dictionary containing data to save
     :type data: dict
     """
-    data['version'] = mopidy.__version__
     directory, basename = os.path.split(path)
 
     # TODO: cleanup directory/basename.* files.