[1.8.x] Fixed #24508 -- Made annotations commutative (3a1886d1) · Commits · Dom Sekotill / django

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")

+8 −0

Original line number	Diff line number	Diff line
		@@ -99,6 +99,14 @@ 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=2)
		Book.objects.annotate(other_rating=F('rating') - 1).update(rating=F('other_rating'))