Django自定义认证后端报app_label相关错误排查与解决

配置自定义认证后端时触发如下报错：

Model class tainfo.apps.users.models.User doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS.

问题场景 #

编写了支持手机号、用户名双登录的自定义认证后端，代码如下：

from django.contrib.auth.backends import ModelBackend
import re
from tainfo.apps.users.models import User


def get_user_by_account(account):
    try:
        if re.match(r'1[3-9]\d{9}',account):
            user = User.objects.get(mobile=account)
        else:
            user = User.objects.get(username=account)
        return user
    except User.DoesNotExist:
        return None

class UsernameMobileAuthBackend(ModelBackend):
    def authenticate(self,request,username=None,password=None,**kwargs):
        user = get_user_by_account(username)
        if user and user.check_password(password) and user.is_active:
            return user

在devsettings.py中添加配置AUTHENTICATION_BACKENDS = ['users.utils.UsernameMobileAuthBackend',]后就会触发上述报错，删除该配置则报错消失，但自定义认证后端的能力也无法生效。

已确认正常的配置项 #

• 自定义User模型正确继承AbstractUser，模型代码如下：

from django.contrib.auth.models import AbstractUser
from django.db import models

# Create your models here.

class User(AbstractUser):
    mobile = models.CharField(max_length=11, unique=True, verbose_name='mobile',blank=True)
    email_active = models.BooleanField(default=False, verbose_name='emailisactive')

    class Meta:
        db_table = 'tb_users'
        verbose_name = 'user'
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.username

• 配置文件基础配置无遗漏：已在INSTALLED_APPS中注册users等应用，已通过AUTH_USER_MODEL指定自定义用户模型，相关配置如下：

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',

    'users.apps.UsersConfig',
    'contents.apps.ContentsConfig',
    'verifications.apps.VerificationsConfig',
]
AUTH_USER_MODEL = 'users.User'
AUTHENTICATION_BACKENDS = ['users.utils.UsernameMobileAuthBackend',]

解决方案 #

报错根因是自定义认证后端中User模型的导入路径错误：项目已将apps目录加入sys.path，导入User模型应使用from users.models import User，而非带全项目层级前缀的from tainfo.apps.users.models import User。修改导入路径后问题即可彻底解决。

内容的提问来源于stack exchange，提问作者Eric YJ Chung