misc: keep cache of queryset result after __iter__ usage (#33013)

tests/test_formdata.py

@@ -786,6 +786,11 @@ def test_lazy_formdata_queryset(pub, variable_test_data):
     for draft in qs:
         assert draft.internal_id == formdata.id
 
+    # check __iter__ creates a cached resultset
+    qs = lazy_formdata.objects.drafts()
+    for formdata1, formdata2 in zip(list(qs), list(qs)):
+        assert formdata1 is formdata2
+
     # check ordering
     qs = lazy_formdata.objects.pending().order_by('id')
     assert [x.number for x in qs] == ['1-1', '1-2', '1-3', '1-4', '1-5', '1-6', '1-7']

wcs/variables.py

@@ -111,18 +111,22 @@ class LazyFormDefObjectsManager(object):
 
     def __getitem__(self, key):
         if self._cached_resultset is None:
-            self._cached_resultset = self._formdef.data_class().select(
-                    clause=self._criterias, order_by=self._order_by)
-        return LazyFormData(self._cached_resultset[key])
+            self._cached_resultset = [LazyFormData(x) for x in
+                    self._formdef.data_class().select(clause=self._criterias, order_by=self._order_by)]
+        return self._cached_resultset[key]
 
     def __iter__(self):
         if self._cached_resultset:
-            for formdata in self._cached_resultset:
-                yield LazyFormData(formdata)
+            for lazy_formdata in self._cached_resultset:
+                yield lazy_formdata
         data_class = self._formdef.data_class()
+        temp_cached_resultset = []
         for formdata in self._formdef.data_class().select_iterator(
                 clause=self._criterias, order_by=self._order_by):
-            yield LazyFormData(formdata)
+            lazy_formdata = LazyFormData(formdata)
+            temp_cached_resultset.append(lazy_formdata)
+            yield lazy_formdata
+        self._cached_resultset = temp_cached_resultset
 
     def __nonzero__(self):
         return any(self)