#27989: Passing an empty QueryDict to a form stores it as a plain dictionary
--------------------------------------------+------------------------
Reporter: Stefan Wehrmeyer | Owner: nobody
Type: Bug | Status: new
Component: Forms | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 1
UI/UX: 0 |
--------------------------------------------+------------------------
Passing an empty {{{request.POST}}} or {{{request.FILES}}} into a form,
evaluates the arguments to {{{False}}}
[https://github.com/django/django/blob/ea36e7454c267aab933e92481288e1eab636cd62/django/forms/forms.py#L79-L80
in these lines] and stores a normal Python dictionary instead.
{{{
self.data = data or {}
self.files = files or {}
}}}
This breaks the assumption that what you pass into the form will be kept
allowing access to special methods like {{{QueryDict.getlist}}}.
The following code accepts zero or more uploaded files, but breaks when no
files are uploaded because the passed {{{QueryDict}}} gets discarded and a
{{{dict}}} has no method {{{getlist}}}.
{{{
class UploadForm(forms.Form):
documents = forms.FileField(
required=False,
widget=forms.FileInput(attrs={
'multiple': True
})
)
def save(self):
for doc in self.files.getlist('documents'):
handle_doc(doc)
form = UploadForm(request.POST, request.FILES)
form.save()
# When request.FILES is empty
# AttributeError: 'dict' object has no attribute 'getlist'
}}}
Instead of
{{{
self.data = data or {}
self.files = files or {}
}}}
it should be something like
{{{
self.data = QueryDict() if data is None else data
self.files = QueryDict() if files is None else files
}}}
which would keep whatever was passed except {{{None}}} and fall back to an
empty {{{QueryDict}}} instance which is the type of the usual parameter.
The only backwards incompatible change here would be that {{{self.data}}}
and {{{self.files}}} are no longer mutable as they would be when set to
empty {{{dict}}}s, but afaik the attributes are not changed anyway.
--
Ticket URL: <https://code.djangoproject.com/ticket/27989>
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