#36548: GeneratedField ignores it's output field "choices" argument
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Reporter: Olivier Dalang | Type: Uncategorized
Status: new | Component: Uncategorized
Version: 5.2 | 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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Hello !
GeneratedFields take the "output_field" argument to define the field's
data type. One can set a CharField with the "choices" argument as output
type.
Unfortunately, the resulting field doesn't behave as a regular CharField
with the choices argument (it seems the "choices" is just ignored).
I don't know all internal implications around GeneratedField and
output_type, but naively I would expect this to work, just as I expect
GeneratedFields of type DateField to output actual python dates. This not
working makes it difficult to transition from/to GeneratedFields in
migration scenarios, prevents nice integration in django admin (such as
labels for filters), and generally requires boilerplate code to map back
to the display value.
Below is a small example to reproduce the issue.
Cheers !!
Olivier
{{{#!python
class YearInSchool(models.TextChoices):
FRESHMAN = "FR", "Freshman"
SOPHOMORE = "SO", "Sophomore"
class MyModel(models.Model):
normal_choice = models.CharField(
choices=YearInSchool, default=YearInSchool.FRESHMAN
)
generated_choice = models.GeneratedField(
expression=models.F("normal_choice"),
output_field=models.CharField(choices=YearInSchool),
db_persist=False,
)
}}}
{{{#!python
myobj = MyModel.objects.create()
myobj.get_normal_choice_display() # works as expected
# 'Freshman'
myobj.get_generated_choice_display() # oh no, non of these choices
goodies :-(
# AttributeError: 'MyModel' object has no attribute
'get_generated_choice_display'.
myobj.normal_choice # works as expected
# YearInSchool.FRESHMAN
myobj.generated_choice # we get the raw string
# 'FR'
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/36548>
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