Commit 127b3873 authored by Josh Smeaton's avatar Josh Smeaton
Browse files

Fixed #24508 -- Made annotations commutative

parent a6bada1e

django/db/models/expressions.py

+12 −2
Original line number Diff line number Diff line
@@ -238,7 +238,16 @@ class BaseExpression(object): 
        """

        Attempts to infer the output type of the expression. If the output

        fields of all source fields match then we can simply infer the same

        type here.

        type here. This isn't always correct, but it makes sense most of the

        time.



        Consider the difference between `2 + 2` and `2 / 3`. Inferring

        the type here is a convenience for the common case. The user should

        supply their own output_field with more complex computations.



        If a source does not have an `_output_field` then we exclude it from

        this check. If all sources are `None`, then an error will be thrown

        higher up the stack in the `output_field` property.

        """

        if self._output_field is None:

            sources = self.get_source_fields()
@@ -246,8 +255,9 @@ class BaseExpression(object): 
            if num_sources == 0:

                self._output_field = None

            else:

                self._output_field = sources[0]

                for source in sources:

                    if self._output_field is None:

                        self._output_field = source

                    if source is not None and not isinstance(self._output_field, source.__class__):

                        raise FieldError(

                            "Expression contains mixed types. You must set output_field")

tests/annotations/tests.py

+8 −0
Original line number Diff line number Diff line
@@ -182,6 +182,14 @@ class NonAggregateAnnotationTestCase(TestCase): 
                sum_rating=Sum('rating')

            ).filter(sum_rating=F('nope')))



    def test_combined_annotation_commutative(self):

        book1 = Book.objects.annotate(adjusted_rating=F('rating') + 2).get(pk=self.b1.pk)

        book2 = Book.objects.annotate(adjusted_rating=2 + F('rating')).get(pk=self.b1.pk)

        self.assertEqual(book1.adjusted_rating, book2.adjusted_rating)

        book1 = Book.objects.annotate(adjusted_rating=F('rating') + None).get(pk=self.b1.pk)

        book2 = Book.objects.annotate(adjusted_rating=None + F('rating')).get(pk=self.b1.pk)

        self.assertEqual(book1.adjusted_rating, book2.adjusted_rating)



    def test_update_with_annotation(self):

        book_preupdate = Book.objects.get(pk=self.b2.pk)

        Book.objects.annotate(other_rating=F('rating') - 1).update(rating=F('other_rating'))