#28575: Model.DoesNotExist classes are not pickleable
-------------------------------------+-------------------------------------
Reporter: Rachel | Owner: nobody
Tobin |
Type: | Status: new
Uncategorized |
Component: Database | Version: 1.11
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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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.
--
Ticket URL: <https://code.djangoproject.com/ticket/28575>
Django <https://code.djangoproject.com/>
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