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

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

Backport of bc87061a3c7c8d6b4d2469f35cc78683c6cff647 from master

4 files changed, 54 insertions, 6 deletions

diff --git a/django/db/models/query_utils.py b/django/db/models/query_utils.py
index ac9405ec73..eca060e667 100644
--- a/django/db/models/query_utils.py
+++ b/django/db/models/query_utils.py
@@ -88,7 +88,7 @@ class Q(tree.Node):
         # We must promote any new joins to left outer joins so that when Q is
         # used as an expression, rows aren't filtered due to joins.
         joins_before = query.tables[:]
-        clause, joins = query._add_q(self, reuse, allow_joins=allow_joins)
+        clause, joins = query._add_q(self, reuse, allow_joins=allow_joins, split_subq=False)
         joins_to_promote = [j for j in joins if j not in joins_before]
         query.promote_joins(joins_to_promote)
         return clause
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index 387b91a60b..6f883031ef 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -1112,7 +1112,7 @@ class Query(object):
                 (name, lhs.output_field.__class__.__name__))
 
     def build_filter(self, filter_expr, branch_negated=False, current_negated=False,
-                     can_reuse=None, connector=AND, allow_joins=True):
+                     can_reuse=None, connector=AND, allow_joins=True, split_subq=True):
         """
         Builds a WhereNode for a single filter clause, but doesn't add it
         to this Query. Query.add_q() will then add this filter to the where
@@ -1161,7 +1161,7 @@ class Query(object):
 
         opts = self.get_meta()
         alias = self.get_initial_alias()
-        allow_many = not branch_negated
+        allow_many = not branch_negated or not split_subq
 
         try:
             field, sources, opts, join_list, path = self.setup_joins(
@@ -1309,7 +1309,7 @@ class Query(object):
         self.demote_joins(existing_inner)
 
     def _add_q(self, q_object, used_aliases, branch_negated=False,
-               current_negated=False, allow_joins=True):
+               current_negated=False, allow_joins=True, split_subq=True):
         """
         Adds a Q-object to the current filter.
         """
@@ -1323,12 +1323,14 @@ class Query(object):
             if isinstance(child, Node):
                 child_clause, needed_inner = self._add_q(
                     child, used_aliases, branch_negated,
-                    current_negated, allow_joins)
+                    current_negated, allow_joins, split_subq)
                 joinpromoter.add_votes(needed_inner)
             else:
                 child_clause, needed_inner = self.build_filter(
                     child, can_reuse=used_aliases, branch_negated=branch_negated,
-                    current_negated=current_negated, connector=connector, allow_joins=allow_joins)
+                    current_negated=current_negated, connector=connector,
+                    allow_joins=allow_joins, split_subq=split_subq,
+                )
                 joinpromoter.add_votes(needed_inner)
             target_clause.add(child_clause, connector)
         needed_inner = joinpromoter.update_join_types(self)
diff --git a/docs/releases/1.8.2.txt b/docs/releases/1.8.2.txt
index 18c1ba38c9..635bc96e92 100644
--- a/docs/releases/1.8.2.txt
+++ b/docs/releases/1.8.2.txt
@@ -18,6 +18,10 @@ Bugfixes
   query with a  ``Case`` expression could unexpectedly filter out results
   (:ticket:`24766`).
 
+* Fixed negated ``Q`` objects in expressions. Cases like
+  ``Case(When(~Q(friends__age__lte=30)))`` tried to generate a subquery which
+  resulted in a crash (:ticket:`24705`).
+
 * Fixed incorrect GROUP BY clause generation on MySQL when the query's model
   has a self-referential foreign key (:ticket:`24748`).
 
diff --git a/tests/expressions_case/tests.py b/tests/expressions_case/tests.py
index d6ff0debb0..58dc7ca80d 100644
--- a/tests/expressions_case/tests.py
+++ b/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