Inject errors into already validated form?
django, django-forms
Solution
`Form._errors` can be treated like a standard dictionary. It's considered good form to use the `ErrorList` class, and to append errors to the existing list:
from django.forms.utils import ErrorList
errors = form._errors.setdefault("myfield", ErrorList())
errors.append(u"My error here")
And if you want to add non-field errors, use `django.forms.forms.NON_FIELD_ERRORS` (defaults to `"__all__"`) instead of `"myfield"`.
Problem
After my `form.Form` validates the user input values I pass them to a separate (external) process for further processing. This external process can potentially find further errors in the values. Is there a way to inject these errors into the already validated form so they can be displayed via the usual form error display methods (or are there better alternative approaches)? One suggestions was to include the external processing in the form validation, which is not ideal because the external process does a lot more than merely validate.