Fixed #26789 -- Fixed handling of empty geometries in BaseSpatialField.get_db_prep_save().

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

@@ -26,6 +26,8 @@ class BaseSpatialFeatures(object):
     supports_real_shape_operations = True
     # Can geometry fields be null?
     supports_null_geometries = True
+    # Are empty geometries supported?
+    supports_empty_geometries = False
     # Can the the function be applied on geodetic coordinate systems?
     supports_distance_geodetic = True
     supports_length_geodetic = True

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

@@ -8,3 +8,4 @@ class DatabaseFeatures(BaseSpatialFeatures, Psycopg2DatabaseFeatures):
     supports_3d_functions = True
     supports_left_right_lookups = True
     supports_raster = True
+    supports_empty_geometries = True

django/contrib/gis/db/models/fields.py

@@ -177,10 +177,10 @@ class BaseSpatialField(Field):
         """
         Prepare the value for saving in the database.
         """
-        if not value:
+        if isinstance(value, Geometry) or value:
-            return None
-        else:
             return connection.ops.Adapter(self.get_prep_value(value))
+        else:
+            return None
 
     def get_raster_prep_value(self, value, is_candidate):
         """

tests/gis_tests/geoapp/tests.py

@@ -6,8 +6,8 @@ import tempfile
 from django.contrib.gis import gdal
 from django.contrib.gis.db.models import Extent, MakeLine, Union
 from django.contrib.gis.geos import (
-    GeometryCollection, GEOSGeometry, LinearRing, LineString, Point, Polygon,
+    GeometryCollection, GEOSGeometry, LinearRing, LineString, MultiLineString,
-    fromstr,
+    MultiPoint, MultiPolygon, Point, Polygon, fromstr,
 )
 from django.core.management import call_command
 from django.db import connection
@@ -215,6 +215,29 @@ class GeoModelTest(TestCase):
             call_command('loaddata', tmp.name, verbosity=0)
         self.assertListEqual(original_data, list(City.objects.all().order_by('name')))
 
+    @skipUnlessDBFeature("supports_empty_geometries")
+    def test_empty_geometries(self):
+        geometry_classes = [
+            Point,
+            LineString,
+            LinearRing,
+            Polygon,
+            MultiPoint,
+            MultiLineString,
+            MultiPolygon,
+            GeometryCollection,
+        ]
+        for klass in geometry_classes:
+            g = klass(srid=4326)
+            feature = Feature.objects.create(name='Empty %s' % klass.__name__, geom=g)
+            feature.refresh_from_db()
+            if klass is LinearRing:
+                # LinearRing isn't representable in WKB, so GEOSGeomtry.wkb
+                # uses LineString instead.
+                g = LineString(srid=4326)
+            self.assertEqual(feature.geom, g)
+            self.assertEqual(feature.geom.srid, g.srid)
+
 
 @skipUnlessDBFeature("gis_enabled")
 class GeoLookupTest(TestCase):