Fixed #15271 -- Defined a to_python method for GeometryField

Thanks volrath and copelco for their work on the patch.

django/contrib/gis/forms/fields.py

@@ -5,7 +5,7 @@ from django.utils.translation import ugettext_lazy as _
 
 # While this couples the geographic forms to the GEOS library,
 # it decouples from database (by not importing SpatialBackend).
-from django.contrib.gis.geos import GEOSGeometry
+from django.contrib.gis.geos import GEOSException, GEOSGeometry
 
 class GeometryField(forms.Field):
     """
@@ -31,6 +31,15 @@ class GeometryField(forms.Field):
         self.null = kwargs.pop('null', True)
         super(GeometryField, self).__init__(**kwargs)
 
+    def to_python(self, value):
+        """
+        Transforms the value to a Geometry object.
+        """
+        try:
+            return GEOSGeometry(value)
+        except (GEOSException, ValueError, TypeError):
+            raise forms.ValidationError(self.error_messages['invalid_geom'])
+
     def clean(self, value):
         """
         Validates that the input value can be converted to a Geometry
@@ -44,11 +53,8 @@ class GeometryField(forms.Field):
             else:
                 raise forms.ValidationError(self.error_messages['no_geom'])
 
-        # Trying to create a Geometry object from the form value.
-        try:
-            geom = GEOSGeometry(value)
-        except:
-            raise forms.ValidationError(self.error_messages['invalid_geom'])
+        # Transform the value to a python object first
+        geom = self.to_python(value)
 
         # Ensuring that the geometry is of the correct type (indicated
         # using the OGC string label).

django/contrib/gis/tests/test_geoforms.py

@@ -56,8 +56,25 @@ class GeometryFieldTest(unittest.TestCase):
 
         pnt_fld = forms.GeometryField(geom_type='POINT')
         self.assertEqual(GEOSGeometry('POINT(5 23)'), pnt_fld.clean('POINT(5 23)'))
+        # a WKT for any other geom_type will be properly transformed by `to_python`
+        self.assertEqual(GEOSGeometry('LINESTRING(0 0, 1 1)'), pnt_fld.to_python('LINESTRING(0 0, 1 1)'))
+        # but rejected by `clean`
         self.assertRaises(forms.ValidationError, pnt_fld.clean, 'LINESTRING(0 0, 1 1)')
 
+    def test04_to_python(self):
+        """
+        Testing to_python returns a correct GEOSGeometry object or
+        a ValidationError
+        """
+        fld = forms.GeometryField()
+        # to_python returns the same GEOSGeometry for a WKT
+        for wkt in ('POINT(5 23)', 'MULTIPOLYGON(((0 0, 0 1, 1 1, 1 0, 0 0)))', 'LINESTRING(0 0, 1 1)'):
+            self.assertEqual(GEOSGeometry(wkt), fld.to_python(wkt))
+        # but raises a ValidationError for any other string
+        for wkt in ('POINT(5)', 'MULTI   POLYGON(((0 0, 0 1, 1 1, 1 0, 0 0)))', 'BLAH(0 0, 1 1)'):
+            self.assertRaises(forms.ValidationError, fld.to_python, wkt)
+
+
 def suite():
     s = unittest.TestSuite()
     s.addTest(unittest.makeSuite(GeometryFieldTest))