#22510: Form fields cannot have names that are present as attributes on the form
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Reporter: gc@… | Owner: nobody
Type: Bug | Status: new
Component: Forms | Version: 1.7-beta-2
Severity: Release blocker | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by loic84):
I've discussed this with @gcbirzan on IRC, there is indeed a regression on
attributes called `media`.
Since `MediaDefiningClass` monkeypatches each subclass with a `media`
attribute, it effectively shadows any field called `media`.
Moving the shadowing before the parent's fields discovery as suggested
above would allow a single Form to have a `media` field, but that wouldn't
work when inheritance is involved anyway.
The problem could also manifest itself with overridden methods that would
clash with a field name:
{{{
Form(forms.Form):
clean = forms.BooleanField()
Form2(Form):
def clean(self):
pass
}}}
Options I can think of:
- Backward incompatible change, care must be taken when subclassing a form
not to accidentally shadow a field with a method, and a special mention
for `media`.
- Change the shadowing logic to use a sentinel value (e.g. `None`, or a
`ShadowField` object).
- A declarative class attribute to list the fields to shadow:
{{{
Form(forms.Form):
something = forms.CharField()
Form2(Form):
shadow_fields = ['something']
}}}
For reference the ticket for field shadowing is #8620.
--
Ticket URL: <https://code.djangoproject.com/ticket/22510#comment:6>
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