Unified LoginView/LogoutView.get_default_redirect_url() methods.

This might change the behavior when self.next_page == "". However,
resolve_url(self.next_page) would almost certainly fail in that case.

It is technically possible to define a logout URLpattern whose name is
"": path('logout/', LogoutView.as_view(), name=''), and then to refer to
this pattern with next_page = "". However this feels like a pathological
case, so we decided not to handle it.

Most checks on next_page, LOGIN_REDIRECT_URL, and LOGOUT_REDIRECT_URL
are performed with boolean evaluation rather than comparison with None.
That's why we standardizing that way.

1 files changed, 13 insertions, 6 deletions

diff --git a/django/contrib/auth/views.py b/django/contrib/auth/views.py
index 25d987d0dc..60ae71b669 100644
--- a/django/contrib/auth/views.py
+++ b/django/contrib/auth/views.py
@@ -85,7 +85,10 @@ class LoginView(RedirectURLMixin, FormView):
 
     def get_default_redirect_url(self):
         """Return the default redirect URL."""
-        return resolve_url(self.next_page or settings.LOGIN_REDIRECT_URL)
+        if self.next_page:
+            return resolve_url(self.next_page)
+        else:
+            return resolve_url(settings.LOGIN_REDIRECT_URL)
 
     def get_form_class(self):
         return self.authentication_form or self.form_class
@@ -151,13 +154,17 @@ class LogoutView(RedirectURLMixin, TemplateView):
     # RemovedInDjango50Warning.
     get = post
 
-    def get_success_url(self):
-        if self.next_page is not None:
-            next_page = resolve_url(self.next_page)
+    def get_default_redirect_url(self):
+        """Return the default redirect URL, or None if no URL is configured."""
+        if self.next_page:
+            return resolve_url(self.next_page)
         elif settings.LOGOUT_REDIRECT_URL:
-            next_page = resolve_url(settings.LOGOUT_REDIRECT_URL)
+            return resolve_url(settings.LOGOUT_REDIRECT_URL)
         else:
-            next_page = self.next_page
+            return None
+
+    def get_success_url(self):
+        next_page = self.get_default_redirect_url()
 
         if (
             self.redirect_field_name in self.request.POST