#30596: Form method `has_changed` always returns True if form has the
SplitArrayField field
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Reporter: Evgeniy Krysanov | Owner: nobody
Type: Bug | Status: new
Component: Forms | Version: 2.2
Severity: Normal | Resolution:
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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Comment (by Evgeniy Krysanov):
Replying to [comment:1 felixxm]:
> I was not able to reproduce this issue in basic tests. Maybe it is
related `remove_trailing_nulls=True`, do you have them in a database? e.g.
`[1.33, 5.33. 8.78, None]` Can you check initial data?
I checked a lot of cases until I isolated the problem -
https://github.com/django/django/blob/master/django/forms/forms.py#L451
`initial_value` is the original object's value, for example [3.5, 1.0,
2.2]. `data_value` is converted from form data to ['3.5', '1.0', '2.2'],
but not converted to FloatField values. If the `initial_value` is [] then
the `data_value` is `['', '', '']`. Thats why `has_changed` always returns
True.
I fixed this bug in my project with the following code:
{{{
class BetterSplitArrayField(SplitArrayField):
def to_python(self, value):
return self.clean(value)
}}}
When calling `field.has_changed(initial_value, data_value)`there is a call
to `data = self.to_python(data)`
https://github.com/django/django/blob/master/django/forms/fields.py#L181
but `SplitArrayField` just return original value from this method. My code
fix this.
But it would be better to see the fix in Django source. I can write a PR
with unitests if you wish.
--
Ticket URL: <https://code.djangoproject.com/ticket/30596#comment:2>
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