Fix DatabaseScheduler behavior when schedule is changed from interval to crontab (celery#351)

* add regression test for ModelEntry.from_entry

* fix ModelEntry.from_entry and ModelEntry.__repr__ behavior

Author: dmitry-mukhin

djcelery/schedulers.py

@@ -120,6 +120,11 @@ def from_entry(cls, name, skip_fields=('relative', 'options'), **entry):
             fields.pop(skip_field, None)
         schedule = fields.pop('schedule')
         model_schedule, model_field = cls.to_model_schedule(schedule)
+
+        # reset schedule
+        for t in cls.model_schedules:
+            fields[t[2]] = None
+
         fields[model_field] = model_schedule
         fields['args'] = dumps(fields.get('args') or [])
         fields['kwargs'] = dumps(fields.get('kwargs') or {})

djcelery/tests/test_schedulers.py

@@ -100,6 +100,21 @@ def test_entry(self):
         self.assertGreater(e3.last_run_at, e2.last_run_at)
         self.assertEqual(e3.total_run_count, 1)
 
+    def test_from_entry(self):
+        name = 'interval-vs-crontab'
+        entry = {'task': 'djcelery.unittest.add{0}'.format(_next_id()),
+                 'args': '[2, 2]',
+                 'schedule': timedelta(hours=24),}
+        self.Entry.from_entry(name, **entry)
+        schedule1 = PeriodicTask.objects.get(name=name).schedule
+        self.assertIsInstance(schedule1, schedule)
+
+        # update schedule
+        entry['schedule'] = crontab(minute=0, hour='*/6')
+        self.Entry.from_entry(name, **entry)
+        schedule2 = PeriodicTask.objects.get(name=name).schedule
+        self.assertIsInstance(schedule2, crontab)
+
 
 class test_DatabaseScheduler(unittest.TestCase):
     Scheduler = TrackingScheduler
@@ -145,8 +160,6 @@ def test_schedule_changed(self):
         self.m1.save()
         e1 = self.s.schedule[self.m1.name]
         self.assertListEqual(e1.args, [32, 32])
-        e1 = self.s.schedule[self.m1.name]
-        self.assertListEqual(e1.args, [32, 32])
 
         self.m3.delete()
         self.assertRaises(KeyError, self.s.schedule.__getitem__, self.m3.name)