Add range nullification

setup.py

@@ -24,7 +24,7 @@ extras_require = {
     'anyjson': ['anyjson>=0.3.3'],
     'babel': ['Babel>=1.3'],
     'arrow': ['arrow>=0.3.4'],
-    'intervals': ['intervals>=0.2.0'],
+    'intervals': ['intervals>=0.2.2'],
     'phone': ['phonenumbers>=5.9.2'],
     'password': ['passlib >= 1.6, < 2.0'],
     'color': ['colour>=0.0.4'],

sqlalchemy_utils/types/range.py

@@ -182,9 +182,10 @@ class RangeType(types.TypeDecorator, ScalarCoercible):
 
     def load_dialect_impl(self, dialect):
         if dialect.name == 'postgresql':
-            # Use the native JSON type.
+            # Use the native range type for postgres.
             return dialect.type_descriptor(self.impl)
         else:
+            # Other drivers don't have native types.
             return dialect.type_descriptor(sa.String(255))
 
     def process_bind_param(self, value, dialect):
@@ -193,7 +194,7 @@ class RangeType(types.TypeDecorator, ScalarCoercible):
         return value
 
     def process_result_value(self, value, dialect):
-        if value:
+        if value is not None:
             if self.interval_class.step is not None:
                 return self.canonicalize_result_value(
                     self.interval_class(value)
@@ -206,9 +207,9 @@ class RangeType(types.TypeDecorator, ScalarCoercible):
         return intervals.canonicalize(value, True, True)
 
     def _coerce(self, value):
-        if value is not None:
-            value = self.interval_class(value)
-        return value
+        if value is None:
+            return None
+        return self.interval_class(value)
 
 
 class IntRangeType(RangeType):

tests/types/test_int_range.py

@@ -32,6 +32,18 @@ class NumberRangeTestCase(TestCase):
         self.session.commit()
         return self.session.query(self.Building).first()
 
+    def test_nullify_range(self):
+        building = self.create_building(None)
+        assert building.persons_at_night == None
+
+    def test_update_with_none(self):
+        interval = intervals.IntInterval('(,)')
+        building = self.create_building(interval)
+        building.persons_at_night = None
+        assert building.persons_at_night is None
+        self.session.commit()
+        assert building.persons_at_night is None
+
     @mark.parametrize(
         'number_range',
         (

tests/types/test_numeric_range.py

@@ -29,6 +29,10 @@ class NumericRangeTestCase(TestCase):
         self.session.commit()
         return self.session.query(self.Car).first()
 
+    def test_nullify_range(self):
+        building = self.create_car(None)
+        assert building.price_range == None
+
     @mark.parametrize(
         'number_range',
         (