Avoid empty notifications when no effective modifications (#1074)

Fix TG-5341

taiga/projects/notifications/services.py

@@ -245,14 +245,20 @@ def send_sync_notifications(notification_id):
     """
 
     notification = HistoryChangeNotification.objects.select_for_update().get(pk=notification_id)
-    # If the last modification is too recent we ignore it
+    # If the last modification is too recent we ignore it for the time being
     now = timezone.now()
     time_diff = now - notification.updated_datetime
     if time_diff.seconds < settings.CHANGE_NOTIFICATIONS_MIN_INTERVAL:
         return
 
     history_entries = tuple(notification.history_entries.all().order_by("created_at"))
-    history_entries = squash_history_entries(history_entries)
+    history_entries = list(squash_history_entries(history_entries))
+
+    # If there are no effective modifications we can delete this notification
+    # without further processing
+    if notification.history_type == HistoryType.change and not history_entries:
+        notification.delete()
+        return
 
     obj, _ = get_last_snapshot_for_key(notification.key)
     obj_class = get_model_from_key(obj.key)

tests/integration/test_notifications.py

@@ -359,7 +359,7 @@ def test_send_notifications_using_services_method_for_user_stories(settings, mai
     history_change = f.HistoryEntryFactory.create(
         project=project,
         user={"pk": member1.user.id},
-        comment="",
+        comment="test:change",
         type=HistoryType.change,
         key="userstories.userstory:{}".format(us.id),
         is_hidden=False,
@@ -454,7 +454,7 @@ def test_send_notifications_using_services_method_for_tasks(settings, mail):
     history_change = f.HistoryEntryFactory.create(
         project=project,
         user={"pk": member1.user.id},
-        comment="",
+        comment="test:change",
         type=HistoryType.change,
         key="tasks.task:{}".format(task.id),
         is_hidden=False,
@@ -549,7 +549,7 @@ def test_send_notifications_using_services_method_for_issues(settings, mail):
     history_change = f.HistoryEntryFactory.create(
         project=project,
         user={"pk": member1.user.id},
-        comment="",
+        comment="test:change",
         type=HistoryType.change,
         key="issues.issue:{}".format(issue.id),
         is_hidden=False,
@@ -644,7 +644,7 @@ def test_send_notifications_using_services_method_for_wiki_pages(settings, mail)
     history_change = f.HistoryEntryFactory.create(
         project=project,
         user={"pk": member1.user.id},
-        comment="",
+        comment="test:change",
         type=HistoryType.change,
         key="wiki.wikipage:{}".format(wiki.id),
         is_hidden=False,