Commit cbcf78fa authored by Y3K's avatar Y3K Committed by Josh Smeaton
Browse files

Fixed #25252 -- Added friendly error message on incorrect .select_related() use 

Using select_related() after .values() or .values_list() is not possible
because .values() or .values_list() already got the values they need.
parent 7a98442f

django/db/models/query.py

+4 −0
Original line number Diff line number Diff line
@@ -843,6 +843,10 @@ class QuerySet(object): 


        If select_related(None) is called, the list is cleared.

        """



        if self._fields is not None:

            raise TypeError("Cannot call select_related() after .values() or .values_list()")



        obj = self._clone()

        if fields == (None,):

            obj.query.select_related = False

tests/select_related/tests.py

+20 −0
Original line number Diff line number Diff line
@@ -163,6 +163,26 @@ class SelectRelatedTests(TestCase): 
            self.assertEqual(obj.parent_1, parent_1)

            self.assertEqual(obj.parent_2, parent_2)



    def test_select_related_after_values(self):

        """

        Running select_related() after calling values() raises a TypeError

        """



        message = "Cannot call select_related() after .values() or .values_list()"



        with self.assertRaisesMessage(TypeError, message):

            list(Species.objects.values('name').select_related('genus'))



    def test_select_related_after_values_list(self):

        """

        Running select_related() after calling values_list() raises a TypeError

        """



        message = "Cannot call select_related() after .values() or .values_list()"



        with self.assertRaisesMessage(TypeError, message):

            list(Species.objects.values_list('name').select_related('genus'))





class SelectRelatedValidationTests(SimpleTestCase):

    """