Fixed #16110 -- Fixed GeometryField odd behaviour regarding null values

Thanks slinkp for the report and the initial patch.

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

@@ -202,7 +202,6 @@ class GeometryField(Field):
 
     def formfield(self, **kwargs):
         defaults = {'form_class' : forms.GeometryField,
-                    'null' : self.null,
                     'geom_type' : self.geom_type,
                     'srid' : self.srid,
                     }

django/contrib/gis/forms/fields.py

@@ -1,5 +1,7 @@
 from __future__ import unicode_literals
 
+import warnings
+
 from django import forms
 from django.utils import six
 from django.utils.translation import ugettext_lazy as _
@@ -18,7 +20,7 @@ class GeometryField(forms.Field):
     widget = forms.Textarea
 
     default_error_messages = {
-        'no_geom' : _('No geometry value provided.'),
+        'required' : _('No geometry value provided.'),
         'invalid_geom' : _('Invalid geometry value.'),
         'invalid_geom_type' : _('Invalid geometry type.'),
         'transform_error' : _('An error occurred when transforming the geometry '
@@ -30,13 +32,18 @@ class GeometryField(forms.Field):
         # defaults (e.g., allow None).
         self.srid = kwargs.pop('srid', None)
         self.geom_type = kwargs.pop('geom_type', 'GEOMETRY')
-        self.null = kwargs.pop('null', True)
+        if 'null' in kwargs:
+            kwargs.pop('null', True)
+            warnings.warn("Passing 'null' keyword argument to GeometryField is deprecated.",
+                DeprecationWarning, stacklevel=2)
         super(GeometryField, self).__init__(**kwargs)
 
     def to_python(self, value):
         """
         Transforms the value to a Geometry object.
         """
+        if value in self.empty_values:
+            return None
         try:
             return GEOSGeometry(value)
         except (GEOSException, ValueError, TypeError):
@@ -48,15 +55,9 @@ class GeometryField(forms.Field):
         object (which is returned).  A ValidationError is raised if
         the value cannot be instantiated as a Geometry.
         """
-        if not value:
-            if self.null and not self.required:
-                # The geometry column allows NULL and is not required.
-                return None
-            else:
-                raise forms.ValidationError(self.error_messages['no_geom'])
-
-        # Transform the value to a python object first
-        geom = self.to_python(value)
+        geom = super(GeometryField, self).clean(value)
+        if geom is None:
+            return geom
 
         # Ensuring that the geometry is of the correct type (indicated
         # using the OGC string label).

django/contrib/gis/tests/test_geoforms.py

@@ -1,6 +1,7 @@
 from django.forms import ValidationError
 from django.contrib.gis.gdal import HAS_GDAL
 from django.contrib.gis.tests.utils import HAS_SPATIALREFSYS
+from django.utils import six
 from django.utils import unittest
 
 
@@ -37,15 +38,13 @@ class GeometryFieldTest(unittest.TestCase):
         "Testing GeometryField's handling of null (None) geometries."
         # Form fields, by default, are required (`required=True`)
         fld = forms.GeometryField()
-        self.assertRaises(forms.ValidationError, fld.clean, None)
-
-        # Still not allowed if `null=False`.
-        fld = forms.GeometryField(required=False, null=False)
-        self.assertRaises(forms.ValidationError, fld.clean, None)
+        with six.assertRaisesRegex(self, forms.ValidationError,
+                "No geometry value provided."):
+            fld.clean(None)
 
         # This will clean None as a geometry (See #10660).
         fld = forms.GeometryField(required=False)
-        self.assertEqual(None, fld.clean(None))
+        self.assertIsNone(fld.clean(None))
 
     def test03_geom_type(self):
         "Testing GeometryField's handling of different geometry types."