[1.8.x] Fixed #26215 -- Fixed RangeField/ArrayField serialization with None values

Also added tests for HStoreField.
Thanks Aleksey Bukin for the report and Tim Graham for the initial patch and
the review.
Backport of 928c12eb1 from master.

django/contrib/postgres/fields/array.py

@@ -95,8 +95,11 @@ class ArrayField(Field):
         base_field = self.base_field
 
         for val in vals:
-            obj = AttributeSetter(base_field.attname, val)
-            values.append(base_field.value_to_string(obj))
+            if val is None:
+                values.append(None)
+            else:
+                obj = AttributeSetter(base_field.attname, val)
+                values.append(base_field.value_to_string(obj))
         return json.dumps(values)
 
     def get_transform(self, name):

django/contrib/postgres/fields/ranges.py

@@ -51,8 +51,12 @@ class RangeField(models.Field):
         base_field = self.base_field
         result = {"bounds": value._bounds}
         for end in ('lower', 'upper'):
-            obj = AttributeSetter(base_field.attname, getattr(value, end))
-            result[end] = base_field.value_to_string(obj)
+            val = getattr(value, end)
+            if val is None:
+                result[end] = None
+            else:
+                obj = AttributeSetter(base_field.attname, val)
+                result[end] = base_field.value_to_string(obj)
         return json.dumps(result)
 
     def formfield(self, **kwargs):

docs/releases/1.8.10.txt

@@ -17,3 +17,7 @@ Bugfixes
 
 * Made ``forms.FileField`` and ``utils.translation.lazy_number()`` picklable
   (:ticket:`26212`).
+
+* Fixed :class:`~django.contrib.postgres.fields.RangeField` and
+  :class:`~django.contrib.postgres.fields.ArrayField` serialization with
+  ``None`` values (:ticket:`26215`).

tests/postgres_tests/test_array.py

@@ -412,16 +412,18 @@ class TestMigrations(TransactionTestCase):
 
 
 class TestSerialization(TestCase):
-    test_data = '[{"fields": {"field": "[\\"1\\", \\"2\\"]"}, "model": "postgres_tests.integerarraymodel", "pk": null}]'
+    test_data = (
+        '[{"fields": {"field": "[\\"1\\", \\"2\\", null]"}, "model": "postgres_tests.integerarraymodel", "pk": null}]'
+    )
 
     def test_dumping(self):
-        instance = IntegerArrayModel(field=[1, 2])
+        instance = IntegerArrayModel(field=[1, 2, None])
         data = serializers.serialize('json', [instance])
         self.assertEqual(json.loads(data), json.loads(self.test_data))
 
     def test_loading(self):
         instance = list(serializers.deserialize('json', self.test_data))[0].object
-        self.assertEqual(instance.field, [1, 2])
+        self.assertEqual(instance.field, [1, 2, None])
 
 
 class TestValidation(TestCase):

tests/postgres_tests/test_hstore.py

@@ -130,7 +130,8 @@ class TestQuerying(TestCase):
 
 
 class TestSerialization(TestCase):
-    test_data = '[{"fields": {"field": "{\\"a\\": \\"b\\"}"}, "model": "postgres_tests.hstoremodel", "pk": null}]'
+    test_data = ('[{"fields": {"field": "{\\"a\\": \\"b\\"}"}, '
+                 '"model": "postgres_tests.hstoremodel", "pk": null}]')
 
     def test_dumping(self):
         instance = HStoreModel(field={'a': 'b'})
@@ -141,6 +142,12 @@ class TestSerialization(TestCase):
         instance = list(serializers.deserialize('json', self.test_data))[0].object
         self.assertEqual(instance.field, {'a': 'b'})
 
+    def test_roundtrip_with_null(self):
+        instance = HStoreModel(field={'a': 'b', 'c': None})
+        data = serializers.serialize('json', [instance])
+        new_instance = list(serializers.deserialize('json', data))[0].object
+        self.assertEqual(instance.field, new_instance.field)
+
 
 class TestValidation(TestCase):
 

tests/postgres_tests/test_ranges.py

@@ -225,6 +225,17 @@ class TestSerialization(TestCase):
         self.assertEqual(instance.floats, NumericRange(empty=True))
         self.assertEqual(instance.bigints, None)
 
+    def test_serialize_range_with_null(self):
+        instance = RangesModel(ints=NumericRange(None, 10))
+        data = serializers.serialize('json', [instance])
+        new_instance = list(serializers.deserialize('json', data))[0].object
+        self.assertEqual(new_instance.ints, NumericRange(None, 10))
+
+        instance = RangesModel(ints=NumericRange(10, None))
+        data = serializers.serialize('json', [instance])
+        new_instance = list(serializers.deserialize('json', data))[0].object
+        self.assertEqual(new_instance.ints, NumericRange(10, None))
+
 
 class TestValidators(TestCase):