validate GeometryField and cleanup intersection errors if possible

src/c3nav/mapdata/fields.py

@@ -1,19 +1,32 @@
 import json
 
+from django.core.exceptions import ValidationError
 from django.db import models
+from shapely import validation
 from shapely.geometry import mapping, shape
+from shapely.geometry.base import BaseGeometry
 
-from c3nav.mapdata.utils import format_geojson
+from c3nav.mapdata.utils import clean_geometry, format_geojson
+
+
+def validate_geometry(geometry):
+    if not isinstance(geometry, BaseGeometry):
+        raise ValidationError('GeometryField expexted a Shapely BaseGeometry child-class.')
+
+    if not geometry.is_valid:
+        raise ValidationError('Invalid geometry: %s' % validation.explain_validity(geometry))
 
 
 class GeometryField(models.TextField):
+    default_validators = [validate_geometry]
+
     def from_db_value(self, value, expression, connection, context):
         if value is None:
             return value
         return shape(json.loads(value))
 
     def to_python(self, value):
-        return shape(json.loads(value))
+        return clean_geometry(shape(json.loads(value)))
 
     def get_prep_value(self, value):
         return json.dumps(format_geojson(mapping(value)))