auth: Improve robustness of not sending duplicate login emails.

Previously, we had a very not-robust check on the URL, which might
have caused cases like Google auth registration to not do the right
thing.

zerver/signals.py

@@ -64,13 +64,9 @@ def email_on_new_login(sender, user, request, **kwargs):
         return
 
     if request:
-        # Login emails are for returning users, not new registrations.
-        # Determine if login request was from new registration.
-        path = request.META.get('PATH_INFO', None)
-
-        if path:
-            if path == "/accounts/register/":
-                return
+        # If the user's account was just created, avoid sending an email.
+        if getattr(user, "just_registered", False):
+            return
 
         login_time = timezone_now().strftime('%A, %B %d, %Y at %I:%M%p ') + \
             timezone_get_current_timezone_name()

zerver/tests/test_new_users.py

@@ -47,9 +47,9 @@ class SendLoginEmailTest(ZulipTestCase):
         with self.settings(SEND_LOGIN_EMAILS=True):
             self.register("test@zulip.com", "test")
 
-            for email in mail.outbox:
-                subject = 'New login from an unknown browser on an unknown operating system'
-                self.assertNotEqual(email.subject, subject)
+            # Verify that there's just 1 email for new user registration.
+            self.assertEqual(mail.outbox[0].subject, "Activate your Zulip account")
+            self.assertEqual(len(mail.outbox), 1)
 
     def test_without_path_info_dont_send_login_emails_for_new_user_registration_logins(self):
         # type: () -> None

zerver/views/registration.py

@@ -244,6 +244,9 @@ def accounts_register(request):
             logging.error("Subdomain mismatch in registration %s: %s" % (
                 realm.subdomain, user_profile.email,))
             return redirect('/')
+
+        # Mark the user as having been just created, so no login email is sent
+        auth_result.just_registered = True
         login(request, auth_result)
         return HttpResponseRedirect(realm.uri + reverse('zerver.views.home.home'))