Groups in a chord throw exception #1509
Description
from celery import Celery
celery = Celery()
celery.config_from_object({
'CELERY_RESULT_BACKEND': 'redis://localhost:6379'
})
from celery import chord, group, task
@task
def test():
return True
c = chord([group(test.si(), test.si()), group(test.si(), test.si())])(group(test.si()))
c.get()
The tasks succeed. The groups throw the following exception:
Traceback (most recent call last):
File "/Library/Python/2.7/site-packages/celery-3.0.21-py2.7.egg/celery/task/trace.py", line 277, in trace_task
on_chord_part_return(task)
File "/Library/Python/2.7/site-packages/celery-3.0.21-py2.7.egg/celery/backends/base.py", line 503, in on_chord_part_return
if val >= len(deps):
TypeError: object of type 'NoneType' has no len()
Granted, the two groups can be rewritten as a single group. it makes it a little harder for composition though. If every application has to rewrite, it would be nice for the framework to do so.