#30564: Cannot create custom field that returns a queryset AND uses pre_save().
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Reporter: Dan J Strohl | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution: invalid
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Changes (by felixxm):
* status: new => closed
* resolution: => invalid
Comment:
> Either way though, the bug I am reporting is that when returning a
django queryset, via a custom field with a pre_save, it raises an
AttributeError. Since these are all normal Django objects, and I'm using
documented django approaches, I see this as a bug.
Your custom field implementation is quite complicated. Custom fields with
`pre_save()` works properly because you can treat any Django's field as a
custom field e.g. `DateField`. It seems (but it is hard to tell without
`pre_save_func()`) that in your case `pre_save()` returns `Query` which is
not expected by `SQLInsertCompiler.prepare_value()`, that's why IMO it is
an issue in your implementation/approach.
> Since these are all normal Django objects.
You cannot assume that Django internals will handle everything, even if
these objects are defined by Django.
I think that `return self.get_db_prep_value(value)` in `pre_save()` in
branch with `pre_save_func()` should fix your issue.
--
Ticket URL: <https://code.djangoproject.com/ticket/30564#comment:5>
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