Fixed #28591 -- Added an error message for createsuperuser --username= (blank).

django/contrib/auth/management/commands/createsuperuser.py

@@ -68,6 +68,7 @@ class Command(BaseCommand):
         # Same as user_data but with foreign keys as fake model instances
         # instead of raw IDs.
         fake_user_data = {}
+        verbose_field_name = self.username_field.verbose_name
 
         # Do quick and dirty validation if --noinput
         if not options['interactive']:
@@ -96,7 +97,6 @@ class Command(BaseCommand):
                     raise NotRunningInTTYException("Not running in a TTY")
 
                 # Get a username
-                verbose_field_name = self.username_field.verbose_name
                 while username is None:
                     input_msg = capfirst(verbose_field_name)
                     if default_username:
@@ -121,6 +121,9 @@ class Command(BaseCommand):
                             self.stderr.write("Error: That %s is already taken." % verbose_field_name)
                             username = None
 
+                if not username:
+                    raise CommandError('%s cannot be blank.' % capfirst(verbose_field_name))
+
                 for field_name in self.UserModel.REQUIRED_FIELDS:
                     field = self.UserModel._meta.get_field(field_name)
                     user_data[field_name] = options[field_name]

tests/auth_tests/test_management.py

@@ -523,6 +523,22 @@ class CreatesuperuserManagementCommandTestCase(TestCase):
 
         test(self)
 
+    def test_blank_username(self):
+        """Creation fails if --username is blank."""
+        new_io = StringIO()
+
+        def test(self):
+            with self.assertRaisesMessage(CommandError, 'Username cannot be blank.'):
+                call_command(
+                    'createsuperuser',
+                    username='',
+                    stdin=MockTTY(),
+                    stdout=new_io,
+                    stderr=new_io,
+                )
+
+        test(self)
+
     def test_invalid_username(self):
         """Creation fails if the username fails validation."""
         user_field = User._meta.get_field(User.USERNAME_FIELD)