adding errors to Django form errors.__all__

Question

How do I add errors to the top of a form after I cleaned the data? I have an object that needs to make a REST call to an external app (google maps) as a pre-save condition, and this can fail, which means I need my users to correct the data in the form. So I clean the data and then try to save and add to the form errors if the save doesn't work:

if request.method == "POST":
#clean form data
    try:
        profile.save()
        return HttpResponseRedirect(reverse("some_page", args=[some.args]))
    except ValueError:
        our_form.errors.__all__ = [u"error message goes here"]
return render_to_response(template_name, {"ourform": our_form,}, 
       context_instance=RequestContext(request))

This failed to return the error text in my unit-tests (which were looking for it in {{form.non_field_errors}}), and then when I run it through the debugger, the errors had not been added to the forms error dict when they reach the render_to_response line, nor anywhere else in the our_form tree. Why didn't this work? How am I supposed to add errors to the top of a form after it's been cleaned?

Answer 1

You should raise the validationerror.

Why not put the verification within the form's clean method

class ProfileForm(forms.Form):
    def clean(self):
        try:
            #Make a call to the API and verify it works well
        except:
            raise forms.ValidationError('Your address is not locatable by Google Maps')

that way, you just need the standard form.is_valid() in the view.

Answer 2

You really want to do this during form validation and raise a ValidationError from there... but if you're set on doing it this way you'll want to access _errors to add new messages. Try something like this:

from django.forms.util import ErrorList

our_form._errors["field_name"] = ErrorList([u"error message goes here"])

Answer 3

I'm not sure how horrible of a hack this is (I've only really worked on two Django projects up until this point) but if you do something like follows you get a separate error message that is not associated with a specific field in the model:

form = NewPostForm()
if something_went_horribly_wrong():
  form.errors[''] = "You broke it!"

Answer 4

Non field errors can be added as 'all' key or constand NON_FIELD_ERRORS:

from django import forms
errors = my_form._errors.setdefault(forms.forms.NON_FIELD_ERRORS, forms.util.ErrorList())
errors.append("My error here")