Added SpatialFeatures.empty_intersection_returns_none.

django/contrib/gis/db/backends/base/features.py

@@ -54,6 +54,10 @@ class BaseSpatialFeatures:
     # Set of options that AsGeoJSON() doesn't support.
     unsupported_geojson_options = {}
 
+    # Does Intersection() return None (rather than an empty GeometryCollection)
+    # for empty results?
+    empty_intersection_returns_none = True
+
     @property
     def supports_bbcontains_lookup(self):
         return 'bbcontains' in self.connection.ops.gis_operators

django/contrib/gis/db/backends/mysql/features.py

@@ -17,8 +17,11 @@ class DatabaseFeatures(BaseSpatialFeatures, MySQLDatabaseFeatures):
     unsupported_geojson_options = {'crs'}
 
     @cached_property
-    def supports_empty_geometry_collection(self):
-        return self.connection.mysql_version >= (5, 7, 5)
+    def empty_intersection_returns_none(self):
+        return (
+            not self.connection.mysql_is_mariadb and
+            self.connection.mysql_version < (5, 7, 5)
+        )
 
     @cached_property
     def supports_geometry_field_unique_index(self):

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

@@ -10,3 +10,4 @@ class DatabaseFeatures(BaseSpatialFeatures, Psycopg2DatabaseFeatures):
     supports_3d_functions = True
     supports_raster = True
     supports_empty_geometries = True
+    empty_intersection_returns_none = False

tests/gis_tests/geoapp/test_functions.py

@@ -12,7 +12,7 @@ from django.db import NotSupportedError, connection
 from django.db.models import IntegerField, Sum, Value
 from django.test import TestCase, skipUnlessDBFeature
 
-from ..utils import FuncTestMixin, mariadb, mysql, oracle, postgis, spatialite
+from ..utils import FuncTestMixin, mariadb, mysql, oracle, postgis
 from .models import City, Country, CountryWebMercator, State, Track
 
 
@@ -295,11 +295,10 @@ class GISFunctionsTests(FuncTestMixin, TestCase):
         geom = Point(5, 23, srid=4326)
         qs = Country.objects.annotate(inter=functions.Intersection('mpoly', geom))
         for c in qs:
-            if spatialite or (mysql and not connection.features.supports_empty_geometry_collection) or oracle:
-                # When the intersection is empty, some databases return None.
-                expected = None
-            else:
-                expected = c.mpoly.intersection(geom)
+            expected = (
+                None if connection.features.empty_intersection_returns_none
+                else c.mpoly.intersection(geom)
+            )
             self.assertEqual(c.inter, expected)
 
     @skipUnlessDBFeature("has_IsValid_function")
@@ -570,8 +569,11 @@ class GISFunctionsTests(FuncTestMixin, TestCase):
             return
         for c in qs:
             self.assertTrue(c.mpoly.difference(geom).equals(c.difference))
-            if not (spatialite or mysql):
-                self.assertEqual(c.mpoly.intersection(geom), c.intersection)
+            expected_intersection = (
+                None if connection.features.empty_intersection_returns_none
+                else c.mpoly.intersection(geom)
+            )
+            self.assertEqual(c.intersection, expected_intersection)
             self.assertTrue(c.mpoly.sym_difference(geom).equals(c.sym_difference))
             self.assertTrue(c.mpoly.union(geom).equals(c.union))