Signals can not connect to OneToOneField.

[954-Ivory]

Because django let sender = self.__class__:
https://github.com/django/django/blob/e9fd2b572410b1236da0d3d0933014138d89f44e/django/db/models/base.py#L860

If you inheritance from PeriodicTask(same as OneToOneField), and overwrite save() in your field, like this:

class YourPeriodicTask(PeriodicTask):
    # ...
    def save(self, *args, **kwargs):
        # ...
        super().save(*args, **kwargs)

The pre_save.sender will be YourPeriodicTask, not PeriodicTask.
So, the signal will not be receive.

[auvipy]

is it bug or what you are suggesting?

[954-Ivory]

is it bug or what you are suggesting?

Yeah, I think it's a bug.
When we change the PeriodicTask in other Model, if signal can not be receive, the schedulers will not do anything.
This breaks field and scheduler consistency.