cache: Clear realm descriptions when description is changed.

Clear both the rendered and the text descriptions for a realm, when the
description of the realm is changed.

zerver/lib/cache.py

@@ -375,47 +375,47 @@ def delete_display_recipient_cache(user_profile: 'UserProfile') -> None:
     keys = [display_recipient_cache_key(rid) for rid in recipient_ids]
     cache_delete_many(keys)
 
+def changed(kwargs: Any, fields: List[str]) -> bool:
+    if kwargs.get('update_fields') is None:
+        # adds/deletes should invalidate the cache
+        return True
+
+    update_fields = set(kwargs['update_fields'])
+    for f in fields:
+        if f in update_fields:
+            return True
+
+    return False
+
 # Called by models.py to flush the user_profile cache whenever we save
 # a user_profile object
 def flush_user_profile(sender: Any, **kwargs: Any) -> None:
     user_profile = kwargs['instance']
     delete_user_profile_caches([user_profile])
 
-    def changed(fields: List[str]) -> bool:
-        if kwargs.get('update_fields') is None:
-            # adds/deletes should invalidate the cache
-            return True
-
-        update_fields = set(kwargs['update_fields'])
-        for f in fields:
-            if f in update_fields:
-                return True
-
-        return False
-
     # Invalidate our active_users_in_realm info dict if any user has changed
     # the fields in the dict or become (in)active
-    if changed(realm_user_dict_fields):
+    if changed(kwargs, realm_user_dict_fields):
         cache_delete(realm_user_dicts_cache_key(user_profile.realm_id))
 
-    if changed(['is_active']):
+    if changed(kwargs, ['is_active']):
         cache_delete(active_user_ids_cache_key(user_profile.realm_id))
         cache_delete(active_non_guest_user_ids_cache_key(user_profile.realm_id))
 
-    if changed(['is_guest']):
+    if changed(kwargs, ['is_guest']):
         cache_delete(active_non_guest_user_ids_cache_key(user_profile.realm_id))
 
-    if changed(['email', 'full_name', 'short_name', 'id', 'is_mirror_dummy']):
+    if changed(kwargs, ['email', 'full_name', 'short_name', 'id', 'is_mirror_dummy']):
         delete_display_recipient_cache(user_profile)
 
     # Invalidate our bots_in_realm info dict if any bot has
     # changed the fields in the dict or become (in)active
-    if user_profile.is_bot and changed(bot_dict_fields):
+    if user_profile.is_bot and changed(kwargs, bot_dict_fields):
         cache_delete(bot_dicts_in_realm_cache_key(user_profile.realm))
 
     # Invalidate realm-wide alert words cache if any user in the realm has changed
     # alert words
-    if changed(['alert_words']):
+    if changed(kwargs, ['alert_words']):
         cache_delete(realm_alert_words_cache_key(user_profile.realm))
         cache_delete(realm_alert_words_automaton_cache_key(user_profile.realm))
 
@@ -438,6 +438,10 @@ def flush_realm(sender: Any, **kwargs: Any) -> None:
         cache_delete(realm_rendered_description_cache_key(realm))
         cache_delete(realm_text_description_cache_key(realm))
 
+    if changed(kwargs, ['description']):
+        cache_delete(realm_rendered_description_cache_key(realm))
+        cache_delete(realm_text_description_cache_key(realm))
+
 def realm_alert_words_cache_key(realm: 'Realm') -> str:
     return "realm_alert_words:%s" % (realm.string_id,)
 

zerver/tests/test_realm.py

@@ -21,6 +21,7 @@ from zerver.lib.actions import (
 )
 
 from confirmation.models import create_confirmation_link, Confirmation
+from zerver.lib.realm_description import get_realm_rendered_description, get_realm_text_description
 from zerver.lib.send_email import send_future_email
 from zerver.lib.test_classes import ZulipTestCase
 from zerver.lib.test_helpers import tornado_redirected_to_list
@@ -185,6 +186,22 @@ class RealmTest(ZulipTestCase):
         do_deactivate_realm(user.realm)
         self.assertEqual(ScheduledEmail.objects.count(), 0)
 
+    def test_do_change_realm_description_clears_cached_descriptions(self) -> None:
+        realm = get_realm('zulip')
+        rendered_description = get_realm_rendered_description(realm)
+        text_description = get_realm_text_description(realm)
+
+        realm.description = 'New Description'
+        realm.save(update_fields=['description'])
+
+        new_rendered_description = get_realm_rendered_description(realm)
+        self.assertNotEqual(rendered_description, new_rendered_description)
+        self.assertIn(realm.description, new_rendered_description)
+
+        new_text_description = get_realm_text_description(realm)
+        self.assertNotEqual(text_description, new_text_description)
+        self.assertEqual(realm.description, new_text_description)
+
     def test_do_deactivate_realm_on_deactivated_realm(self) -> None:
         """Ensure early exit is working in realm deactivation"""
         realm = get_realm('zulip')