X-Git-Url: https://git.madduck.net/etc/taskwarrior.git/blobdiff_plain/58921ff492b989ac597f13f7306e8ae4cda15826..4fe98a10e3269bbd7c43449041d1b7fcd2cbbc8a:/tasklib/task.py

diff --git a/tasklib/task.py b/tasklib/task.py
index a0b3c28..9b3626d 100644
--- a/tasklib/task.py
+++ b/tasklib/task.py
@@ -29,6 +29,18 @@ class SerializingObject(object):
     """
     Common ancestor for TaskResource & TaskFilter, since they both
     need to serialize arguments.
+
+    Serializing method should hold the following contract:
+      - any empty value (meaning removal of the attribute)
+        is deserialized into a empty string
+      - None denotes a empty value for any attribute
+
+    Deserializing method should hold the following contract:
+      - None denotes a empty value for any attribute (however,
+        this is here as a safeguard, TaskWarrior currently does
+        not export empty-valued attributes) if the attribute
+        is not iterable (e.g. list or set), in which case
+        a empty iterable should be used.
     """
 
     def _deserialize(self, key, value):
@@ -43,7 +55,7 @@ class SerializingObject(object):
 
     def timestamp_serializer(self, date):
         if not date:
-            return None
+            return ''
         return date.strftime(DATE_FORMAT)
 
     def timestamp_deserializer(self, date_str):
@@ -98,9 +110,10 @@ class SerializingObject(object):
             return tags.split(',') if tags else []
         return tags or []
 
-    def serialize_depends(self, cur_dependencies):
+    def serialize_depends(self, value):
         # Return the list of uuids
-        return ','.join(task['uuid'] for task in cur_dependencies)
+        value = value if value is not None else set()
+        return ','.join(task['uuid'] for task in value)
 
     def deserialize_depends(self, raw_uuids):
         raw_uuids = raw_uuids or ''  # Convert None to empty string
@@ -317,7 +330,7 @@ class Task(TaskResource):
 
     def serialize_depends(self, cur_dependencies):
         # Check that all the tasks are saved
-        for task in cur_dependencies:
+        for task in (cur_dependencies or set()):
             if not task.saved:
                 raise Task.NotSaved('Task \'%s\' needs to be saved before '
                                     'it can be set as dependency.' % task)