Django的RegexValidator失敗的空字符串

Question

我添加了一個自定義的驗證了我的用戶名場，

我正則表達式是，^[a-zA-Z0-9_]{1,15}$我需要驗證A-Z，0-9和_（下劃線），長度1-15。

def validate_username(value): 
    valid_username = r'^[a-zA-Z0-9_]{1,15}$' 
    validator = RegexValidator(regex=valid_username, message='a-z0-9 [1-15].', code='Invalid Name') 
    validator(value) 
    return value 

這是對save()驗證，

def save(self, **kwargs): 
    if self.username: 
     self.username = validate_username(self.username) 

    super(AbstractBaseUser, self).save(**kwargs) 

這完全適用於Django的外殼，

>>> from django.core.validators import RegexValidator 
>>> valid_username = r'^[a-zA-Z0-9_]{1,15}$' 
>>> validator = RegexValidator(regex=valid_username, message='alphanumerics and underscores are allowed [1-15].', 
           code='Invalid Name') 
>>> validator('') 
Traceback (most recent call last): 
    File "<input>", line 1, in <module> 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/core/validators.py", line 61, in __call__ 
    raise ValidationError(self.message, code=self.code) 
ValidationError: [u'alphanumerics and underscores are allowed [1-15].'] 

，但是當我嘗試創建與用戶名作爲""殼用戶。

>>> x = User.objects.create(email="me@localhost.com", username="") 
>>> x.username 
'' 
>>> x = User.objects.create(email="me@localhosted.com", username="") 
Traceback (most recent call last): 
    File "<input>", line 1, in <module> 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/models/manager.py", line 122, in manager_method 
    return getattr(self.get_queryset(), name)(*args, **kwargs) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/models/query.py", line 401, in create 
    obj.save(force_insert=True, using=self.db) 
    File "/home/marty/projects/cleo/applications/auth/users/models.py", line 85, in save 
    super(AbstractBaseUser, self).save(**kwargs) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/models/base.py", line 708, in save 
    force_update=force_update, update_fields=update_fields) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/models/base.py", line 736, in save_base 
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/models/base.py", line 820, in _save_table 
    result = self._do_insert(cls._base_manager, using, fields, update_pk, raw) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/models/base.py", line 859, in _do_insert 
    using=using, raw=raw) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/models/manager.py", line 122, in manager_method 
    return getattr(self.get_queryset(), name)(*args, **kwargs) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/models/query.py", line 1039, in _insert 
    return query.get_compiler(using=using).execute_sql(return_id) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 1060, in execute_sql 
    cursor.execute(sql, params) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 79, in execute 
    return super(CursorDebugWrapper, self).execute(sql, params) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 64, in execute 
    return self.cursor.execute(sql, params) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/utils.py", line 95, in __exit__ 
    six.reraise(dj_exc_type, dj_exc_value, traceback) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 64, in execute 
    return self.cursor.execute(sql, params) 
    File "/home/marty/.virtualenvs/jk/local/lib/python2.7/site-packages/django/db/backends/sqlite3/base.py", line 323, in execute 
    return Database.Cursor.execute(self, query, params) 
IntegrityError: UNIQUE constraint failed: users_user.username 

第一次它允許我創建一個空字符串作爲用戶名的用戶，第二次它引發了完整性錯誤。我希望系統提高""上的完整性錯誤作爲用戶名。

我在做什麼錯？

Answer 1

的validator在save方法不會被調用時字符串爲空：

if self.username: # an empty string will not pass this condition 
    self.username = validate_username(self.username)