Fixed bug sending always all data to users, who get restricted data

Due to changes in an iterator, a RuntimeError was thrown but interpred al a too low change id. Fixed the bug and make a custom exception for this.

openslides/utils/cache.py

@@ -22,6 +22,10 @@ from .utils import get_element_id, split_element_id
 logger = logging.getLogger(__name__)
 
 
+class ChangeIdTooLowError(Exception):
+    pass
+
+
 def get_all_cachables() -> List[Cachable]:
     """
     Returns all element of OpenSlides.
@@ -274,7 +278,7 @@ class ElementCache:
         Only returns elements with the change_id or newer. When change_id is 0,
         all elements are returned.
 
-        Raises a RuntimeError when the lowest change_id in redis is higher then
+        Raises a ChangeIdTooLowError when the lowest change_id in redis is higher then
         the requested change_id. In this case the method has to be rerun with
         change_id=0. This is importend because there could be deleted elements
         that the cache does not know about.
@@ -288,9 +292,8 @@ class ElementCache:
         if change_id < lowest_change_id:
             # When change_id is lower then the lowest change_id in redis, we can
             # not inform the user about deleted elements.
-            raise RuntimeError(
-                f"change_id {change_id} is lower then the lowest change_id in redis {lowest_change_id}. "
-                "Catch this exception and rerun the method with change_id=0."
+            raise ChangeIdTooLowError(
+                f"change_id {change_id} is lower then the lowest change_id in redis {lowest_change_id}."
             )
 
         raw_changed_elements, deleted_elements = await self.cache_provider.get_data_since(
@@ -302,7 +305,9 @@ class ElementCache:
         }
 
         if user_id is not None:
-            for collection_string, elements in changed_elements.items():
+            # the list(...) is important, because `changed_elements` will be
+            # altered during iteration and restricting data
+            for collection_string, elements in list(changed_elements.items()):
                 restricter = self.cachables[collection_string].restrict_elements
                 restricted_elements = await restricter(user_id, elements)
 
@@ -332,8 +337,6 @@ class ElementCache:
     async def get_lowest_change_id(self) -> int:
         """
         Returns the lowest change id.
-
-        Raises a RuntimeError if there is no change_id.
         """
         return await self.cache_provider.get_lowest_change_id()
 

openslides/utils/consumers.py

@@ -7,7 +7,7 @@ from ..utils.websocket import WEBSOCKET_CHANGE_ID_TOO_HIGH
 from . import logging
 from .auth import async_anonymous_is_enabled
 from .autoupdate import AutoupdateFormat
-from .cache import element_cache, split_element_id
+from .cache import ChangeIdTooLowError, element_cache, split_element_id
 from .utils import get_worker_id
 from .websocket import ProtocollAsyncJsonWebsocketConsumer
 
@@ -138,7 +138,7 @@ class SiteConsumer(ProtocollAsyncJsonWebsocketConsumer):
             changed_elements, deleted_element_ids = await element_cache.get_data_since(
                 user_id, change_id, max_change_id
             )
-        except RuntimeError:
+        except ChangeIdTooLowError:
             # The change_id is lower the the lowerst change_id in redis. Return all data
             changed_elements = await element_cache.get_all_data_list(user_id)
             all_data = True

tests/unit/utils/test_cache.py

@@ -3,7 +3,7 @@ from typing import Any, Dict, List
 
 import pytest
 
-from openslides.utils.cache import ElementCache
+from openslides.utils.cache import ChangeIdTooLowError, ElementCache
 
 from .cache_provider import TTestCacheProvider, example_data, get_cachable_provider
 
@@ -156,7 +156,7 @@ async def test_get_data_since_change_id_lower_than_in_redis(element_cache):
     }
     element_cache.cache_provider.default_change_id = 2
     element_cache.cache_provider.change_id_data = {2: {"app/collection1:1"}}
-    with pytest.raises(RuntimeError):
+    with pytest.raises(ChangeIdTooLowError):
         await element_cache.get_data_since(None, 1)
 
 
@@ -283,7 +283,7 @@ async def test_get_restricted_data_2(element_cache):
 async def test_get_restricted_data_change_id_lower_than_in_redis(element_cache):
     element_cache.cache_provider.default_change_id = 2
 
-    with pytest.raises(RuntimeError):
+    with pytest.raises(ChangeIdTooLowError):
         await element_cache.get_data_since(0, 1)