#29855: Admin form crashes when limit_choices_to query returns non-distinct
results
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Reporter: Karolis Ryselis | Owner: nobody
Type: Uncategorized | Status: new
Component: Forms | Version: 2.1
Severity: Normal | 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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consider the following models:
{{{
class Warehouse(models.Model):
branch = models.ManyToManyField(to="Branch")
class Branch(models.Model):
title = models.CharField(max_length=32)
class Order(models.Model):
warehouses = models.ForeignKey(to="Warehouse",
limit_choices_to={"branch__title__startswith": "A"},
on_delete=models.PROTECT)
}}}
All models are registered using default `admin.ModelAdmin`.
Consider the following data entered:
Branch with name "A branch"
Branch with name "Another branch"
Warehouse related to both branches.
When trying to add a new order, the same warehouse is duplicated two times
in the select box. When trying to save it, it crashes with error
{{{
get() returned more than one Warehouse -- it returned 2!
}}}
The function that crashes is `apply_limit_choices_to_to_formfield`. It
performs a complex query with whatever we passed to `limit_choices_to` in
field declaration and the result is not a distinct queryset. It is
possible to work around this by creating a form for `Order`, overriding
its `__init__` and adding `self.fields["warehouse"].queryset =
self.fields["warehouse"].queryset.distinct()`. However, I think that this
should at least not crash.
--
Ticket URL: <https://code.djangoproject.com/ticket/29855>
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