MultiValueField does not render correctly with as_hidden
|Reported by:||bthomas||Owned by:||nobody|
|Has patch:||yes||Needs documentation:||no|
|Needs tests:||yes||Patch needs improvement:||no|
MultiValueField needs to define hidden_widget = MultipleHiddenInput so that it will work properly when rendered with as_hidden(). However, MultipleHiddenInput still doesn't render IDs the same way as MultiWidget does, so MultiWidget's value_from_datadict will not find the values that MultipleHiddenInput has rendered. Or something like that. I'm concerned that trying to fix MultipleHiddenInput to work with MultiValueField will break MultipleChoiceField, so fixing this may require another Widget class.
A concrete example for this is using form preview with a SplitDateTimeField. The preview page renders all fields with as_hidden(), which creates a field like
<input type="hidden" name="delay_start" value="[u'2008-08-29', u'00:00:00']" id="formtools_delay_start" />
...which can't be turned back into valid data. It needs to render multiple hidden fields like:
<input type="hidden" name="delay_start_0" value="2008-08-29" id="formtools_delay_start_0" /> <input type="hidden" name="delay_start_1" value="00:00:00" id="formtools_delay_start_1" />
Using MultipleHiddenInput creates 2 hidden fields, but does not append the _i to each name and ID, so the data still does not get read back correctly by the form.