Merge pull request #160 from django-json-api/bugfix/none-value-fields

Adds tests for extract_attributes and fixes read_only fields rendering None

Author: jsenecal

example/tests/unit/test_utils.py

@@ -111,6 +111,20 @@ def test_build_json_resource_obj():
     assert utils.build_json_resource_obj(
         serializer.fields, resource, resource_instance, 'user') == output
 
+def test_extract_attributes():
+    fields = {
+        'id': serializers.Field(),
+        'username': serializers.Field(),
+        'deleted': serializers.ReadOnlyField(),
+    }
+    resource = {'id': 1, 'deleted': None, 'username': 'jerel'}
+    expected = {
+        'username': 'jerel',
+        'deleted': None
+    }
+    assert sorted(utils.extract_attributes(fields, resource)) == sorted(expected), 'Regular fields should be extracted'
+    assert sorted(utils.extract_attributes(fields, {})) == sorted({'username': ''}), 'Should not extract read_only fields on empty serializer'
+
 
 class SerializerWithIncludedSerializers(EntrySerializer):
     included_serializers = {

rest_framework_json_api/utils.py

@@ -239,10 +239,14 @@ def extract_attributes(fields, resource):
         if isinstance(field, (RelatedField, BaseSerializer, ManyRelatedField)):
             continue
 
-        # Skip read_only attribute fields when the resource is non-existent
-        # Needed for the "Raw data" form of the browseable API
-        if resource.get(field_name) is None and fields[field_name].read_only:
-            continue
+        # Skip read_only attribute fields when `resource` is an empty
+        # serializer. Prevents the "Raw Data" form of the browseable API
+        # from rendering `"foo": null` for read only fields
+        try:
+            resource[field_name]
+        except KeyError:
+            if fields[field_name].read_only:
+                continue
 
         data.update({
             field_name: resource.get(field_name)