Add class to Django label_tag() output

A custom template tag seems to be the solution. A custom filter would also do, although it can be less elegant. But you would need to fall back to custom form rendering in both cases.

If this is a task of high importance; I'd create a Mixin that allows me to annotate the form fields with label classes and supplies form rendering methods using those classes. So that the following code works:

{{ form.as_table_with_label_classes }}

But I'd like to ask; Do you really need a class on the label tag? I mean HTML design-wise. Is it absolutely necessary to add a class in there? Couldn't it be solved with some CSS like:

encapsulating_selector label {
    some-attr: some-value;
}

I sometimes use jQuery for such cases where; it will improve the page if it works, but it won't be a disaster if it doesn't. And keep the HTML source as lean as possible.

Technique 1

I take issue with another answer's assertion that a filter would be "less elegant." As you can see, it's very elegant indeed.

@register.filter(is_safe=True)
def label_with_classes(value, arg):

    return value.label_tag(attrs={'class': arg})

Using this in a template is just as elegant:

{{ form.my_field|label_with_classes:"class1 class2"}}

Technique 2

Alternatively, one of the more interesting technique I've found is: Adding * to required fields.

You create a decorator for BoundField.label_tag that will call it with attrs set appropriately. Then you monkey patch BoundField so that calling BoundField.label_tag calls the decorated function.

from django.forms.forms import BoundField

def add_control_label(f):
    def control_label_tag(self, contents=None, attrs=None):
        if attrs is None: attrs = {}
        attrs['class'] = 'control-label'
        return f(self, contents, attrs) 
    return control_label_tag

BoundField.label_tag = add_control_label(BoundField.label_tag)    

I am agree with answer number one, with css this could be done, but. What is the reason for this to be in django source?

In django.forms.forms.py there's this definition that shows there's code to display attrs in labels:

class BoundField(StrAndUnicode): 
    ...
    def label_tag(self, contents=None, attrs=None):
        contents = u'<label for="%s"%s>%s</label>' % (widget.id_for_label(id_), attrs, unicode(contents))

but _html_output calls this function without attrs:

label = bf.label_tag(label) or ''

So it seems that django is partially prepared to do this but actually it does not use it.

How about adding the CSS class to the form field in the forms.py, like:

class MyForm(forms.Form):
    title = forms.CharField(widget=forms.TextInput(attrs={'class': 'foo'}))

then I just do the following in the template:

<label for="id_{{form.title.name}}" class="bar">
    {{ form.title }}
</label>

Of course this can easily be modified to work within a for loop tag in the template.