#28575: Model.DoesNotExist classes are not pickleable
-------------------------------------+-------------------------------------
Reporter: Rachel Tobin | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Description changed by Rachel Tobin:
Old description:
> Example:
> {{{
> >>> import django
> >>> import pickle
> >>> pickle.dumps(django.contrib.auth.models.User.DoesNotExist)
> >>> PicklingError: Can't pickle <class
> 'django.contrib.auth.models.DoesNotExist'>: it's not found as
> django.contrib.auth.models.DoesNotExist
> }}}
>
> Note that *instances* of `Model.DoesNotExist` are pickleable as fixed
> here: https://code.djangoproject.com/ticket/17776. However the class
> itself is not. This is particularly problematic when using the Django
> test runner with the `--parallel` option enabled when a
> `Model.DoesNotExist` exception is raised. The result of this is the test
> runner bailing with a `pickle.PicklingError`, making it exceptionally
> difficult to debug the cause of the `Model.DoesNotExist`.
>
> This could be fixed by changing the metaclass that is used here:
> https://github.com/django/django/blob/1.11.5/django/db/models/base.py#L76
> to use a custom metaclass with a `__reduce__` method. A patch is in
> progress for this.
New description:
Example:
{{{
>>> import django
>>> import pickle
>>> pickle.dumps(django.contrib.auth.models.User.DoesNotExist)
>>> PicklingError: Can't pickle <class
'django.contrib.auth.models.DoesNotExist'>: it's not found as
django.contrib.auth.models.DoesNotExist
}}}
Note that *instances* of `Model.DoesNotExist` are pickleable as fixed
here: https://code.djangoproject.com/ticket/17776. However the class
itself is not. This is particularly problematic when using the Django
test runner with the `--parallel` option enabled when a
`Model.DoesNotExist` exception is raised. The result of this is the test
runner bailing with a `pickle.PicklingError`, making it exceptionally
difficult to debug the cause of the `Model.DoesNotExist`.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/28575#comment:2>
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