Fixed last_modified date for item updated on term

django/website/data_layer/models.py

@@ -55,6 +55,13 @@ Item = Message
 @receiver(models.signals.m2m_changed, sender=Item.terms.through,
           dispatch_uid="data_layer.models.terms_signal_handler")
 def terms_signal_handler(sender, **kwargs):
-    if kwargs.get('action') == 'post_add':
-        instance = kwargs.get('instance')
-        instance.note_external_modification()
+    if kwargs.get('action') != 'post_add':
+        return
+
+    if kwargs.get('reverse'):
+        items = Item.objects.filter(pk__in=kwargs.get('pk_set'))
+    else:
+        items = [kwargs.get('instance')]
+
+    for item in items:
+        item.note_external_modification()

django/website/data_layer/tests/item_tests.py

@@ -56,10 +56,22 @@ def test_last_modified_date_updates_on_body_change(item, mock_time_now):
 
 
 @pytest.mark.django_db
-def test_last_modified_date_updates_on_category_change(item, mock_time_now):
+def test_last_modified_date_updates_on_item_category_change(
+        item, mock_time_now):
     with patch('django.utils.timezone.now', new=mock_time_now):
         orig_last_modified = last_modified(item)
         term = TermFactory()
         item.terms.add(term)
 
         assert num_updates(orig_last_modified, last_modified(item)) == 1
+
+
+@pytest.mark.django_db
+def test_last_modified_date_updates_on_category_item_change(
+        item, mock_time_now):
+    with patch('django.utils.timezone.now', new=mock_time_now):
+        orig_last_modified = last_modified(item)
+        term = TermFactory()
+        term.items.add(item)
+
+        assert num_updates(orig_last_modified, last_modified(item)) == 1