Add GeometrySizeValidator to limit area

spillway/validators.py

@@ -0,0 +1,21 @@
+from django import forms
+from django.utils.deconstruct import deconstructible
+from django.utils.translation import ugettext_lazy as _
+
+
+@deconstructible
+class GeometrySizeValidator(object):
+    """Field validator to limit geometries to a given area."""
+    message = _('Max area exceeded.')
+    code = 'invalid'
+
+    def __init__(self, max_area, srid=None):
+        self.max_area = max_area
+        self.srid = srid
+
+    def __call__(self, geom):
+        if self.srid and geom.srid != self.srid:
+            geom.transform(self.srid)
+        if (getattr(geom, 'ogr', geom).dimension > 1 and
+                geom.area > self.max_area):
+            raise forms.ValidationError(self.message, code=self.code)

tests/test_fields.py

@@ -8,6 +8,7 @@
 
 from spillway.forms.fields import OGRGeometryField, GeometryFileField
 from spillway.collections import Feature, NamedCRS
+from spillway.validators import GeometrySizeValidator
 from .models import _geom
 
 
@@ -41,6 +42,11 @@ def test_feature_srid(self):
     def test_invalid(self):
         self.assertRaises(forms.ValidationError, self.field.to_python, '3')
 
+    def test_size_validator(self):
+        validator = GeometrySizeValidator(3 ** 2, 4326)
+        field = OGRGeometryField(validators=[validator])
+        self.assertRaises(forms.ValidationError, field.clean, '0,0,5,5')
+
     def test_srid(self):
         srid = 4269
         geom = OGRGeometryField(srid=srid).to_python('POINT(0 0)')