Django form validation errors being duplicated

Question

I have the following form in django:

class UserEmailRegistrationForm(forms.Form):
    password = forms.PasswordField(max_length=32, label=_('Password'),
                                   validators=[validators.validate_password])
    email = forms.EmailField(label=_('Email'), 
                             validators=[validators.validate_email])
    first_name = forms.CharField(max_length=35, label=_('First name'), 
                                 validators=[validators.validate_name])
    last_name = forms.CharField(max_length=35, label=_('Last name'), 
                                validators=[validators.validate_name])

Most validators are custom, but validate_email is as seen in django.core.validators. Also, here's the relevant part of my view:

form = UserEmailRegistrationForm(PUT)       
    # Validate incoming data
    if not form.is_valid():
        return HttpResponse(form.errors.as_json(), 
                            content_type='application/json', status=422)

All validators are working fine, but I get Enter a valid email address. twice in form.errors when I pass along an invalid email address. Here's the response I get:

{"email": [{"message": "Enter a valid email address.", "code": "invalid"}, {"message": "Enter a valid email address.", "code": "invalid"}]}

What could be causing this and how can I resolve it?

mhawke · Accepted Answer · 2014-10-07 10:06:09Z

3

To debug / see what's happening. In your IDE click on EmailField and follow the hierarchy...

1.Your code:

email = forms.EmailField(label=_('Email'), 
                         validators=[validators.validate_email])

2.EmailField:

class EmailField(CharField):
    widget = EmailInput
    default_validators = [validators.validate_email]

3.CharField / nothing interesting.

class CharField(Field): ...

4.Field.__init__(...):

...
self.validators = self.default_validators + validators
super(Field, self).__init__()

In short, you're using validate_email twice.

edited Oct 7, 2014 at 10:06

mhawke

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answered Oct 7, 2014 at 5:32

François Constant

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1 Comment

André Fratelli Over a year ago

Fixed it! It's a strange behaviour, though. Maybe the parameter should be called something like "extra_validators", it seams more reasonable.

mhawke · Accepted Answer · 2014-10-07 10:44:19Z

As François intimated, there a two identical validators associated with your email field. The first is there by default, and then you add a second one by supplying a value for the validators keyword argument (validators=[validators.validate_email]). This validator list is appended to any default ones. Hence you are seeing 2 validation error messages.

$ python manage.py shell
>>> from django import forms
>>> from django.core import validators
>>> email = forms.EmailField(label=_('Email'), validators=[validators.validate_email])
>>> email.validators
[<django.core.validators.EmailValidator object at 0x2bc0190>, <django.core.validators.EmailValidator object at 0x2bc0190>]

So you can see above that there are 2 registered validators. When the form is validated both are executed:

>>> email.run_validators('[email protected]')
>>> email.run_validators('abc')
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/mhawke/virtualenvs/django_1.6/lib/python2.7/site-packages/django/forms/fields.py", line 139, in run_validators
    raise ValidationError(errors)
ValidationError: [u'Enter a valid email address.', u'Enter a valid email address.']

To fix, simply declare the email field without the validator:

>>> email = forms.EmailField(label=_('Email'))
>>> email.validators
[<django.core.validators.EmailValidator object at 0x2bc0190>]
>>> email.run_validators('[email protected]')
>>> email.run_validators('abc')
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/mhawke/virtualenvs/django_1.6/lib/python2.7/site-packages/django/forms/fields.py", line 139, in run_validators
    raise ValidationError(errors)
ValidationError: [u'Enter a valid email address.']

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