Fixed #26823 -- Prevented update_last_login signal receiver from crashing if User model doesn't have last_login field.

django/contrib/auth/apps.py

@@ -3,8 +3,10 @@ from django.core import checks
 from django.db.models.signals import post_migrate
 from django.utils.translation import gettext_lazy as _
 
+from . import get_user_model
 from .checks import check_models_permissions, check_user_model
 from .management import create_permissions
+from .signals import user_logged_in
 
 
 class AuthConfig(AppConfig):
@@ -16,5 +18,8 @@ class AuthConfig(AppConfig):
             create_permissions,
             dispatch_uid="django.contrib.auth.management.create_permissions"
         )
+        if hasattr(get_user_model(), 'last_login'):
+            from .models import update_last_login
+            user_logged_in.connect(update_last_login, dispatch_uid='update_last_login')
         checks.register(check_user_model, checks.Tags.models)
         checks.register(check_models_permissions, checks.Tags.models)

django/contrib/auth/models.py

@@ -1,6 +1,5 @@
 from django.contrib import auth
 from django.contrib.auth.base_user import AbstractBaseUser, BaseUserManager
-from django.contrib.auth.signals import user_logged_in
 from django.contrib.contenttypes.models import ContentType
 from django.core.exceptions import PermissionDenied
 from django.core.mail import send_mail
@@ -21,9 +20,6 @@ def update_last_login(sender, user, **kwargs):
     user.save(update_fields=['last_login'])
 
 
-user_logged_in.connect(update_last_login)
-
-
 class PermissionManager(models.Manager):
     use_in_migrations = True
 

tests/auth_tests/models/__init__.py

@@ -4,6 +4,7 @@ from .custom_user import (
 )
 from .invalid_models import CustomUserNonUniqueUsername
 from .is_active import IsActiveTestUser1
+from .minimal import MinimalUser
 from .uuid_pk import UUIDUser
 from .with_foreign_key import CustomUserWithFK, Email
 from .with_integer_username import IntegerUsernameUser
@@ -11,5 +12,6 @@ from .with_integer_username import IntegerUsernameUser
 __all__ = (
     'CustomUser', 'CustomUserWithoutIsActiveField', 'CustomPermissionsUser',
     'CustomUserWithFK', 'Email', 'ExtensionUser', 'IsActiveTestUser1',
-    'UUIDUser', 'CustomUserNonUniqueUsername', 'IntegerUsernameUser'
+    'MinimalUser', 'UUIDUser', 'CustomUserNonUniqueUsername',
+    'IntegerUsernameUser',
 )

tests/auth_tests/models/minimal.py

@@ -0,0 +1,6 @@
+from django.db import models
+
+
+class MinimalUser(models.Model):
+    REQUIRED_FIELDS = ()
+    USERNAME_FIELD = 'id'

tests/auth_tests/test_signals.py

@@ -1,8 +1,12 @@
+from django.apps import apps
 from django.contrib.auth import authenticate, signals
 from django.contrib.auth.models import User
+from django.core.exceptions import FieldDoesNotExist
 from django.test import TestCase, override_settings
 from django.test.client import RequestFactory
 
+from .models import MinimalUser
+
 
 @override_settings(ROOT_URLCONF='auth_tests.urls')
 class SignalTestCase(TestCase):
@@ -82,3 +86,23 @@ class SignalTestCase(TestCase):
     def test_failed_login_without_request(self):
         authenticate(username='testclient', password='bad')
         self.assertIsNone(self.login_failed[0]['request'])
+
+    def test_login_with_custom_user_without_last_login_field(self):
+        """
+        The user_logged_in signal is only registered if the user model has a
+        last_login field.
+        """
+        last_login_receivers = signals.user_logged_in.receivers
+        try:
+            signals.user_logged_in.receivers = []
+            with self.assertRaises(FieldDoesNotExist):
+                MinimalUser._meta.get_field('last_login')
+            with self.settings(AUTH_USER_MODEL='auth_tests.MinimalUser'):
+                apps.get_app_config('auth').ready()
+            self.assertEqual(signals.user_logged_in.receivers, [])
+
+            with self.settings(AUTH_USER_MODEL='auth.User'):
+                apps.get_app_config('auth').ready()
+            self.assertEqual(len(signals.user_logged_in.receivers), 1)
+        finally:
+            signals.user_logged_in.receivers = last_login_receivers