[1.9.x] Fixed #26153 -- Reallowed Q-objects in ForeignObject.get_extra_descriptor_filter().

Backport of 353aecbf8c1a8cc6f3985149e2895d49e53dfc1c from master

5 files changed, 39 insertions, 3 deletions

diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index 211c1cdf86..31434864cd 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -8,6 +8,7 @@ from django.apps import apps
 from django.core import checks, exceptions
 from django.db import connection, router
 from django.db.backends import utils
+from django.db.models import Q
 from django.db.models.deletion import CASCADE, SET_DEFAULT, SET_NULL
 from django.db.models.query_utils import PathInfo
 from django.db.models.utils import make_model_tuple
@@ -332,8 +333,13 @@ class RelatedField(Field):
             rh_field.attname: getattr(obj, lh_field.attname)
             for lh_field, rh_field in self.related_fields
         }
-        base_filter.update(self.get_extra_descriptor_filter(obj) or {})
-        return base_filter
+        descriptor_filter = self.get_extra_descriptor_filter(obj)
+        base_q = Q(**base_filter)
+        if isinstance(descriptor_filter, dict):
+            return base_q & Q(**descriptor_filter)
+        elif descriptor_filter:
+            return base_q & descriptor_filter
+        return base_q
 
     @property
     def swappable_setting(self):
diff --git a/django/db/models/fields/related_descriptors.py b/django/db/models/fields/related_descriptors.py
index e9caa2680f..abfa7283ae 100644
--- a/django/db/models/fields/related_descriptors.py
+++ b/django/db/models/fields/related_descriptors.py
@@ -164,7 +164,7 @@ class ForwardManyToOneDescriptor(object):
                 rel_obj = None
             else:
                 qs = self.get_queryset(instance=instance)
-                qs = qs.filter(**self.field.get_reverse_related_filter(instance))
+                qs = qs.filter(self.field.get_reverse_related_filter(instance))
                 # Assuming the database enforces foreign keys, this won't fail.
                 rel_obj = qs.get()
                 # If this is a one-to-one relation, set the reverse accessor
diff --git a/docs/releases/1.9.3.txt b/docs/releases/1.9.3.txt
index 994a018fbc..61a92878c7 100644
--- a/docs/releases/1.9.3.txt
+++ b/docs/releases/1.9.3.txt
@@ -17,3 +17,7 @@ Bugfixes
 
 * Added system checks for query name clashes of hidden relationships
   (:ticket:`26162`).
+
+* Fixed a regression for cases where
+  ``ForeignObject.get_extra_descriptor_filter()`` returned a ``Q`` object
+  (:ticket:`26153`).
diff --git a/tests/foreign_object/models/article.py b/tests/foreign_object/models/article.py
index f0c2f3fbac..6e16784d2c 100644
--- a/tests/foreign_object/models/article.py
+++ b/tests/foreign_object/models/article.py
@@ -44,6 +44,11 @@ class ActiveTranslationField(models.ForeignObject):
         setattr(cls, self.name, ArticleTranslationDescriptor(self))
 
 
+class ActiveTranslationFieldWithQ(ActiveTranslationField):
+    def get_extra_descriptor_filter(self, instance):
+        return models.Q(lang=get_language())
+
+
 @python_2_unicode_compatible
 class Article(models.Model):
     active_translation = ActiveTranslationField(
@@ -54,6 +59,14 @@ class Article(models.Model):
         on_delete=models.CASCADE,
         null=True,
     )
+    active_translation_q = ActiveTranslationFieldWithQ(
+        'ArticleTranslation',
+        from_fields=['id'],
+        to_fields=['article'],
+        related_name='+',
+        on_delete=models.CASCADE,
+        null=True,
+    )
     pub_date = models.DateField()
 
     def __str__(self):
diff --git a/tests/foreign_object/tests.py b/tests/foreign_object/tests.py
index bcdadc6d6d..c838ae4b66 100644
--- a/tests/foreign_object/tests.py
+++ b/tests/foreign_object/tests.py
@@ -467,3 +467,16 @@ class TestModelCheckTests(SimpleTestCase):
                 apps = test_apps
 
         self.assertEqual(Child._meta.get_field('parent').check(from_model=Child), [])
+
+
+class TestExtraJoinFilterQ(TestCase):
+    @translation.override('fi')
+    def test_extra_join_filter_q(self):
+        a = Article.objects.create(pub_date=datetime.datetime.today())
+        ArticleTranslation.objects.create(article=a, lang='fi', title='title', body='body')
+        qs = Article.objects.all()
+        with self.assertNumQueries(2):
+            self.assertEqual(qs[0].active_translation_q.title, 'title')
+        qs = qs.select_related('active_translation_q')
+        with self.assertNumQueries(1):
+            self.assertEqual(qs[0].active_translation_q.title, 'title')