Commit 7ec330ee authored by Simon Charette's avatar Simon Charette
Browse files

Refs #26565 -- Errored nicely when using Prefetch with a values() queryset. 

Thanks Maxime Lorant for the report and Anssi for the suggestion.
parent 8a47ba67

django/db/models/query.py

+2 −0
Original line number Diff line number Diff line
@@ -1331,6 +1331,8 @@ class Prefetch(object): 
        self.prefetch_through = lookup

        # `prefetch_to` is the path to the attribute that stores the result.

        self.prefetch_to = lookup

        if queryset is not None and queryset._iterable_class is not ModelIterable:

            raise ValueError('Prefetch querysets cannot use values().')

        if to_attr:

            self.prefetch_to = LOOKUP_SEP.join(lookup.split(LOOKUP_SEP)[:-1] + [to_attr])

tests/prefetch_related/tests.py

+4 −0
Original line number Diff line number Diff line
@@ -733,6 +733,10 @@ class CustomPrefetchTests(TestCase): 
        self.assertEqual(str(warns[0].message), msg)

        self.assertEqual(str(warns[0].message), msg)



    def test_values_queryset(self):

        with self.assertRaisesMessage(ValueError, 'Prefetch querysets cannot use values().'):

            Prefetch('houses', House.objects.values('pk'))





class DefaultManagerTests(TestCase):