#26807: Custom fields do not call to_python on assignment
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Reporter: akx | Owner: nobody
Type: Uncategorized | Status: new
Component: Database layer (models, ORM) | Version: 1.9
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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With the deprecation of `SubfieldBase`, custom fields no longer
automatically have the `Creator` class behavior that calls `to_python()`
on every assignment (see
https://github.com/django/django/blob/4fd264b6f1737b0317fdd95b3d7ff3bba15ae6c3/django/db/models/fields/subclassing.py#L44),
incl. construction.
This causes the problem described here – https://github.com/hzdg/django-
enumfields/issues/60 – i.e. `enumfields.EnumField` doesn't coerce values
to the actual `Enum` value types anymore.
The fix is naturally to reimplement a descriptor like `Creator` (and that
does indeed fix this particular issue), but I feel like I'm missing
something doing that.
(The deprecation warning for SubfieldBase says that one should use
`from_db_value()`, but it doesn't get called on instance construction
either, it seems.)
Here's a trivial py.test style test case (the assertions fail):
{{{
from django.db import models
class CoolCharField(models.CharField):
def to_python(self, value):
return str(value).upper() + "!!!"
def from_db_value(self, value):
return self.to_python(value)
class CoolModel(models.Model):
yay = CoolCharField()
def test_cool_char_field_1():
m = CoolModel(yay="ponies")
assert m.yay == "PONIES!!!"
def test_cool_char_field_2():
m = CoolModel()
m.yay = "ponies"
assert m.yay == "PONIES!!!"
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/26807>
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