Django: Change formset error message(s)

Question

Hello fellow programmers,

I would like to change the min_num error message of a formset.

My code creates a formset using an inlineformset_factory:

formset_clazz = inlineformset_factory(MyParentModel, MyModel, MyModelForm, can_delete=True, min_num=1, validate_min=True) 
formset = formset_clazz(data=request.POST)
print(formset._non_form_errors)
if formset.is_valid():
    print("yay!")
else:
    print("nay!")
return render(request, "mytemplate.html", {'formset':formset})

In the template I render the non_form_errors:

  {% if formset.non_form_errors %}
  <ul>
    {% for error in form.non_form_errors %}
      <li>
        {{ error }}
      </li>
    {% endfor %}
  </ul>
  {% endif %}

The min_num validation works as intended and shows the error message Please submit 1 or more forms., when a user removes all forms and submits the formset.

My question is: How do I change the error message?

From [0] I learned, that it is stored in formset._non_form_errors, but without a way to override the too_few_forms [1] (ctrl-F validate_min) code's message. The BaseFormSet class itself uses ngettext to translate the message, but I do not really want to setup internationalization just for this (or is that easy and straight-forward?).

Is there a more convenient way to achieve my goal?

[0] Django: Displaying formset errors correctly

[1] https://docs.djangoproject.com/en/2.0/_modules/django/forms/formsets/#BaseFormSet

Answer 1

You can do it in full_clean method of your formset class. Not pretty, but works.

class CheeseStickFormset(BaseFormSet):

    def full_clean(self):
        super(CheeseStickFormset, self).full_clean()

        for error in self._non_form_errors.as_data():
            if error.code == 'too_many_forms':
                error.message = "Please eat %d or fewer cheese sticks." % self.max_num
            if error.code == 'too_few_forms':
                error.message = "Please eat at least %d cheese sticks." % self.min_num