Fixed #13147 -- Moved User validation logic from form to model.

django/contrib/auth/forms.py

@@ -74,16 +74,8 @@ class UserCreationForm(forms.ModelForm):
     password.
     """
     error_messages = {
-        'duplicate_username': _("A user with that username already exists."),
         'password_mismatch': _("The two password fields didn't match."),
     }
-    username = forms.RegexField(label=_("Username"), max_length=30,
-        regex=r'^[\w.@+-]+$',
-        help_text=_("Required. 30 characters or fewer. Letters, digits and "
-                    "@/./+/-/_ only."),
-        error_messages={
-            'invalid': _("This value may contain only letters, numbers and "
-                         "@/./+/-/_ characters.")})
     password1 = forms.CharField(label=_("Password"),
         widget=forms.PasswordInput)
     password2 = forms.CharField(label=_("Password confirmation"),
@@ -94,19 +86,6 @@ class UserCreationForm(forms.ModelForm):
         model = User
         fields = ("username",)
 
-    def clean_username(self):
-        # Since User.username is unique, this check is redundant,
-        # but it sets a nicer error message than the ORM. See #13147.
-        username = self.cleaned_data["username"]
-        try:
-            User._default_manager.get(username=username)
-        except User.DoesNotExist:
-            return username
-        raise forms.ValidationError(
-            self.error_messages['duplicate_username'],
-            code='duplicate_username',
-        )
-
     def clean_password2(self):
         password1 = self.cleaned_data.get("password1")
         password2 = self.cleaned_data.get("password2")
@@ -126,13 +105,6 @@ class UserCreationForm(forms.ModelForm):
 
 
 class UserChangeForm(forms.ModelForm):
-    username = forms.RegexField(
-        label=_("Username"), max_length=30, regex=r"^[\w.@+-]+$",
-        help_text=_("Required. 30 characters or fewer. Letters, digits and "
-                    "@/./+/-/_ only."),
-        error_messages={
-            'invalid': _("This value may contain only letters, numbers and "
-                         "@/./+/-/_ characters.")})
     password = ReadOnlyPasswordHashField(label=_("Password"),
         help_text=_("Raw passwords are not stored, so there is no way to see "
                     "this user's password, but you can change the password "

django/contrib/auth/models.py

@@ -383,8 +383,14 @@ class AbstractUser(AbstractBaseUser, PermissionsMixin):
         help_text=_('Required. 30 characters or fewer. Letters, digits and '
                     '@/./+/-/_ only.'),
         validators=[
-            validators.RegexValidator(r'^[\w.@+-]+$', _('Enter a valid username.'), 'invalid')
+            validators.RegexValidator(r'^[\w.@+-]+$',
-        ])
+                                      _('Enter a valid username. '
+                                        'This value may contain only letters, numbers '
+                                        'and @/./+/-/_ characters.'), 'invalid'),
+        ],
+        error_messages={
+            'unique': _("A user with that username already exists."),
+        })
     first_name = models.CharField(_('first name'), max_length=30, blank=True)
     last_name = models.CharField(_('last name'), max_length=30, blank=True)
     email = models.EmailField(_('email address'), blank=True)

django/contrib/auth/tests/test_forms.py

@@ -4,7 +4,6 @@ import os
 import re
 
 from django import forms
-from django.contrib.auth import get_user_model
 from django.contrib.auth.models import User
 from django.contrib.auth.forms import (UserCreationForm, AuthenticationForm,
     PasswordChangeForm, SetPasswordForm, UserChangeForm, PasswordResetForm,
@@ -36,7 +35,7 @@ class UserCreationFormTest(TestCase):
         form = UserCreationForm(data)
         self.assertFalse(form.is_valid())
         self.assertEqual(form["username"].errors,
-                         [force_text(form.error_messages['duplicate_username'])])
+                         [force_text(User._meta.get_field('username').error_messages['unique'])])
 
     def test_invalid_data(self):
         data = {
@@ -46,8 +45,8 @@ class UserCreationFormTest(TestCase):
         }
         form = UserCreationForm(data)
         self.assertFalse(form.is_valid())
-        self.assertEqual(form["username"].errors,
+        validator = next(v for v in User._meta.get_field('username').validators if v.code == 'invalid')
-                         [force_text(form.fields['username'].error_messages['invalid'])])
+        self.assertEqual(form["username"].errors, [force_text(validator.message)])
 
     def test_password_verification(self):
         # The verification password is incorrect.
@@ -190,8 +189,7 @@ class AuthenticationFormTest(TestCase):
             username = CharField()
 
         form = CustomAuthenticationForm()
-        UserModel = get_user_model()
+        username_field = User._meta.get_field(User.USERNAME_FIELD)
-        username_field = UserModel._meta.get_field(UserModel.USERNAME_FIELD)
         self.assertEqual(form.fields['username'].label, capfirst(username_field.verbose_name))
 
     def test_username_field_label_empty_string(self):
@@ -291,8 +289,8 @@ class UserChangeFormTest(TestCase):
         data = {'username': 'not valid'}
         form = UserChangeForm(data, instance=user)
         self.assertFalse(form.is_valid())
-        self.assertEqual(form['username'].errors,
+        validator = next(v for v in User._meta.get_field('username').validators if v.code == 'invalid')
-                         [force_text(form.fields['username'].error_messages['invalid'])])
+        self.assertEqual(form["username"].errors, [force_text(validator.message)])
 
     def test_bug_14242(self):
         # A regression test, introduce by adding an optimization for the

docs/releases/1.8.txt

@@ -414,6 +414,10 @@ Miscellaneous
   parameters. Internally, Django will continue to provide the
   ``pk`` parameter in ``params`` for backwards compatibility.
 
+* ``UserCreationForm.errors_messages['duplicate_username']`` is no longer used.
+  If you wish to customize that error message, use
+  ``User.error_messages['unique']`` instead.
+
 .. _deprecated-features-1.8:
 
 Features deprecated in 1.8