[1.8.x] Fixed #24705 -- Fixed negated Q objects in expressions.

Avoided split_exclude() for Q when used as an expression.

Backport of bc87061a3c from master

tests/expressions_case/tests.py

@@ -1063,6 +1063,48 @@ class CaseExpressionTests(TestCase):
             lambda x: (x, x.foo)
         )
 
+    def test_m2m_exclude(self):
+        CaseTestModel.objects.create(integer=10, integer2=1, string='1')
+        qs = CaseTestModel.objects.values_list('id', 'integer').annotate(
+            cnt=models.Sum(
+                Case(When(~Q(fk_rel__integer=1), then=1), default=2),
+                output_field=models.IntegerField()
+            ),
+        ).order_by('integer')
+        # The first o has 2 as its fk_rel__integer=1, thus it hits the
+        # default=2 case. The other ones have 2 as the result as they have 2
+        # fk_rel objects, except for integer=4 and integer=10 (created above).
+        # The integer=4 case has one integer, thus the result is 1, and
+        # integer=10 doesn't have any and this too generates 1 (instead of 0)
+        # as ~Q() also matches nulls.
+        self.assertQuerysetEqual(
+            qs,
+            [(1, 2), (2, 2), (2, 2), (3, 2), (3, 2), (3, 2), (4, 1), (10, 1)],
+            lambda x: x[1:]
+        )
+
+    def test_m2m_reuse(self):
+        CaseTestModel.objects.create(integer=10, integer2=1, string='1')
+        # Need to use values before annotate so that Oracle will not group
+        # by fields it isn't capable of grouping by.
+        qs = CaseTestModel.objects.values_list('id', 'integer').annotate(
+            cnt=models.Sum(
+                Case(When(~Q(fk_rel__integer=1), then=1), default=2),
+                output_field=models.IntegerField()
+            ),
+        ).annotate(
+            cnt2=models.Sum(
+                Case(When(~Q(fk_rel__integer=1), then=1), default=2),
+                output_field=models.IntegerField()
+            ),
+        ).order_by('integer')
+        self.assertEqual(str(qs.query).count(' JOIN '), 1)
+        self.assertQuerysetEqual(
+            qs,
+            [(1, 2, 2), (2, 2, 2), (2, 2, 2), (3, 2, 2), (3, 2, 2), (3, 2, 2), (4, 1, 1), (10, 1, 1)],
+            lambda x: x[1:]
+        )
+
 
 class CaseDocumentationExamples(TestCase):
     @classmethod