#14039: FileField special-casing breaks MultiValueField including a FileField
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Reporter: carljm | Owner: carljm
Status: new | Milestone:
Component: Forms | Version: SVN
Keywords: | Stage: Unreviewed
Has_patch: 0 |
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There are a couple places where !FileField is special-cased using {{{
isinstance }}} in the forms code: specifically, in
[[http://code.djangoproject.com/browser/django/trunk/django/forms/forms.py#L280
BaseForm._clean_fields]], a !FileField's clean method is passed the
initial value as well as the data, and in
[[http://code.djangoproject.com/browser/django/trunk/django/forms/forms.py#L438
BoundField.as_widget ]] the initial value is used as the rendered data
even when the form is bound.
This handling of !FileFields is correct, and makes them behave more
naturally with redisplayed bound forms. But, as usual, the use of {{{
isinstance }}} makes things more brittle than necessary. Specifically, in
[[http://bitbucket.org/carljm/django-form-utils django-form-utils]] I've
implemented a !ClearableFileField via !MultiValueField and !MultiWidget
(because the !ClearableFileField contains both a !FileField and a checkbox
for clearing it). The isinstance special-casing means the
!ClearableFileField can't get the right behavior to parallel a !FileField
(because it's not a !FileField subclass, it's a !MultiValueField subclass
containing a !FileField).
It would be better if the special !FileField behavior were implemented
with a class attribute flag or a polymorphic method on Field, rather than
an {{{ isinstance }}} check, so that any field could trigger the
appropriate behavior regardless of its inheritance ancestry.
(This is obviously low priority, not expecting anyone else to work on it,
just recording it here as a I may find some time to work on a patch).
--
Ticket URL: <http://code.djangoproject.com/ticket/14039>
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