Avoid looking up the facility user twice if not needed.

Ensure we don't error when exact username duplicates exist in a facility.

kolibri/core/auth/api.py

@@ -878,7 +878,23 @@ def create(self, request):
                 status=status.HTTP_401_UNAUTHORIZED,
             )
 
-        # Find the FacilityUser we're looking for use later on
+        user = None
+        if interface.enabled and valid_app_key_on_request(request):
+            # If we are in app context, then try to get the automatically created OS User
+            # if it matches the username, without needing a password.
+            user = self._check_os_user(request, username)
+        if user is None:
+            # Otherwise attempt full authentication
+            user = authenticate(
+                username=username, password=password, facility=facility_id
+            )
+        if user is not None and user.is_active:
+            # Correct password, and the user is marked "active"
+            login(request, user)
+            # Success!
+            return self.get_session_response(request)
+        # Otherwise, try to give a helpful error message
+        # Find the FacilityUser we're looking for
         try:
             unauthenticated_user = FacilityUser.objects.get(
                 username__iexact=username, facility=facility_id
@@ -898,24 +914,9 @@ def create(self, request):
             )
         except FacilityUser.MultipleObjectsReturned:
             # Handle case of multiple matching usernames
-            unauthenticated_user = FacilityUser.objects.get(
+            unauthenticated_user = FacilityUser.objects.filter(
                 username__exact=username, facility=facility_id
-            )
-        user = None
-        if interface.enabled and valid_app_key_on_request(request):
-            # If we are in app context, then try to get the automatically created OS User
-            # if it matches the username, without needing a password.
-            user = self._check_os_user(request, username)
-        if user is None:
-            # Otherwise attempt full authentication
-            user = authenticate(
-                username=username, password=password, facility=facility_id
-            )
-        if user is not None and user.is_active:
-            # Correct password, and the user is marked "active"
-            login(request, user)
-            # Success!
-            return self.get_session_response(request)
+            ).first()
         if unauthenticated_user.password == NOT_SPECIFIED:
             # Here - we have a Learner whose password is "NOT_SPECIFIED" because they were created
             # while the "Require learners to log in with password" setting was disabled - but now

kolibri/core/auth/test/test_api.py

@@ -1180,9 +1180,34 @@ def test_case_insensitive_matching_usernames(self):
         # Assert the expected behavior for the second user
         self.assertEqual(response_user2.status_code, 200)
 
-        # Cleanup: Delete the created users
-        self.user1.delete()
-        self.user2.delete()
+    def test_case_sensitive_matching_usernames(self):
+        FacilityUserFactory.create(username="shared_username", facility=self.facility)
+
+        response_user2 = self.client.post(
+            reverse("kolibri:core:session-list"),
+            data={
+                "username": "shared_username",
+                "password": DUMMY_PASSWORD,
+                "facility": self.facility.id,
+            },
+            format="json",
+        )
+
+        # Assert the expected behavior for the second user
+        self.assertEqual(response_user2.status_code, 200)
+
+        # Test no error when authentication fails
+        response_user3 = self.client.post(
+            reverse("kolibri:core:session-list"),
+            data={
+                "username": "shared_username",
+                "password": "wrong_password",
+                "facility": self.facility.id,
+            },
+            format="json",
+        )
+
+        self.assertEqual(response_user3.status_code, 401)
 
 
 class SignUpBase(object):