Save session only if dirty

issue2388
review221006

trytond/wizard/wizard.py

@@ -152,6 +152,7 @@ class _SessionRecord(object):
         self._model = model
         self._data = data
         self.__cache = {}
+	self.dirty = False
 
     def __getattr__(self, name):
         if name in self.__cache:
@@ -182,6 +183,7 @@ class _SessionRecord(object):
                     or name in self._model._inherit_fields)):
             self.__cache.pop(name, None)
             self._data[name] = value
+	    self.dirty = True
         else:
             super(_SessionRecord, self).__setattr__(name, value)
 
@@ -204,12 +206,18 @@ class Session(object):
                 setattr(self, state_name,
                     _SessionRecord(model, self.data[state_name]))
 
+    @property
+    def dirty(self):
+        return any(getattr(self, state_name).dirty
+	    for state_name in self.data)
+
     def save(self):
         "Save the session in database"
         session_obj = Pool().get('ir.session.wizard')
-        session_obj.write(self._session.id, {
-                'data': json.dumps(self.data, cls=JSONEncoder),
-                })
+	if self.dirty:
+            session_obj.write(self._session.id, {
+                    'data': json.dumps(self.data, cls=JSONEncoder),
+                    })
 
 
 class Wizard(WarningErrorMixin, URLMixin):