Django: How to override unique_together error message?

Question

In a model's Meta class, I define a unique_together. I have a ModelForm based on this model. When I call is_valid on this ModelForm, an error will automatically raised if unique_together validation fails. That's all good.

Now my problem is that I'm not satisfied with the default unique_together error message. I want to override it. How can I do that? For a field related error, I can easily do that by setting error_messages on the field parameters. But unique_together is a non field error. How can I override a non field error message?

Answer 1

After a quick check, it seems that unique_together validation errors are hard-coded deep in django.db.models.Model.unique_error_message :

def unique_error_message(self, model_class, unique_check):
    opts = model_class._meta
    model_name = capfirst(opts.verbose_name)

    # A unique field
    if len(unique_check) == 1:
        field_name = unique_check[0]
        field_label = capfirst(opts.get_field(field_name).verbose_name)
        # Insert the error into the error dict, very sneaky
        return _(u"%(model_name)s with this %(field_label)s already exists.") %  {
            'model_name': unicode(model_name),
            'field_label': unicode(field_label)
        }
    # unique_together
    else:
        field_labels = map(lambda f: capfirst(opts.get_field(f).verbose_name), unique_check)
        field_labels = get_text_list(field_labels, _('and'))
        return _(u"%(model_name)s with this %(field_label)s already exists.") %  {
            'model_name': unicode(model_name),
            'field_label': unicode(field_labels)
        }

So maybe you should try to override this method from your model, to insert your own message !?

However, I haven't tried, and it seems a rather brutal solution ! But if you don't have something better, you might try...

Answer 2

If what sebpiq is true( since i do not check source code), then there is one possible solution you can do, but it is the hard way...

You can define a validation rule in your form, as it described here

You can see examples of validation with more than one field, so by using this method, you can define a unique together check before standard django unique check executed...

Or the worst one, you can do a validation in your view before you try to save the objects...

Answer 3

You might take a look at overriding django/db/models/base.py:Model._perform_unique_checks() in your model.

In that method you can get the "original" errors:

    errors = super(MyModel, self)._perform_unique_checks(unique_checks)

-- then modify and return them upwards.