Fixed #27014 -- Fixed annotations with database functions on PostGIS.

Thanks Sean Mc Allister for providing a test.

django/contrib/gis/db/backends/postgis/adapter.py

@@ -15,7 +15,7 @@ class PostGISAdapter(object):
         """
         Initialize on the spatial object.
         """
-        self.is_geometry = isinstance(obj, Geometry)
+        self.is_geometry = isinstance(obj, (Geometry, PostGISAdapter))
 
         # Getting the WKB (in string form, to allow easy pickling of
         # the adaptor) and the SRID from the geometry or raster.

docs/releases/1.10.1.txt

@@ -48,3 +48,6 @@ Bugfixes
 
 * Fixed ``ClearableFileInput`` to avoid the ``required`` HTML attribute when
   initial data exists (:ticket:`27037`).
+
+* Fixed annotations with database functions when combined with lookups on
+  PostGIS (:ticket:`27014`).

tests/gis_tests/geogapp/tests.py

@@ -142,6 +142,9 @@ class GeographyFunctionTests(TestCase):
         qs = Zipcode.objects.annotate(distance=Distance('poly', htown.point))
         for z, ref in zip(qs, ref_dists):
             self.assertAlmostEqual(z.distance.m, ref, 2)
+        # Distance function in combination with a lookup.
+        hzip = Zipcode.objects.get(code='77002')
+        self.assertEqual(qs.get(distance__lte=0), hzip)
 
     @skipUnlessDBFeature("has_Area_function", "supports_distance_geodetic")
     def test_geography_area(self):