Forms (and formsets) don't always generate valid HTML for hidden fields

[Malcolm Tredinnick]

Creating a form with only hidden fields and than calling as_p() on it generates invalid (X)HTML. The input elements must reside inside certain block-level elements and this doesn't always happen. In r9067 I made a change that made this work when displaying error messages for such fields, but the general case is trickier.

The problem is that we can't just apply the same change as r9067 because that would introduce, for example, an empty table row in the as_table() method. This normally wouldn't be an issue (why, exactly, are you calling as_p() on a form that doesn't display anything?), but it arises fairly naturally with formsets. The management form for formsets is a form that only contains hidden fields. Thus, any formset display is slightly invalid. Fixing this doesn't appear to be entirely trivial, so I didn't drop in any kind of patch around the time of r9067.

There are some tests in regressiontests/forms/forms.py that actually demonstrate the problem here: except they consider the invalid output to be valid. So any patch fixing this will cause a couple of tests for hidden fields to "fail" and the tests will need to be fixed.

[anonymous]

When using ajax to load a formset, this can cause improper rendering in the browser. In my case the formset content is sent using HttpResponse(formset.as_table(),mimetype='application/text'). The management form at the beginning of the formset is not in a <tr>. The result is that the tr tags are removed from the entire formset (by the browser when jQuery.html(data) is called).

[Nate]

Replying to anonymous:

When using ajax to load a formset, this can cause improper rendering in the browser. In my case the formset content is sent using HttpResponse(formset.as_table(),mimetype='application/text'). The management form at the beginning of the formset is not in a <tr>. The result is that the tr tags are removed from the entire formset (by the browser when jQuery.html(data) is called).

The following jQuery patched this specific case:
function fixManagement(astable) {

var mngForm = astable.split('<tr>', 1);
var trIndex = astable.indexOf('<th>',1)+4;
var latter = astable.substr(trIndex);
return '<tr><th>'+ mngForm + latter;

}

[Aleksandra Sendecka]

I could not reproduce the bug, but I'm not sure, if I understand the ticket well. Does anybody have an example that generates invalid (X)HTML?

[Tim Graham]

I'm also not sure how to reproduce this. This seems fine:

>>> from django import forms
>>> 
>>> class Foo(forms.Form):
...     baz = forms.CharField(widget=forms.HiddenInput)
...     bar =  forms.CharField(widget=forms.HiddenInput)
... 
>>> foo = Foo()
>>> foo.as_p()
'<input id="id_baz" name="baz" type="hidden" /><input id="id_bar" name="bar" type="hidden" />'

Maybe things have changed since 7 years ago when the ticket was reported.