Avoided that an empty attributes dict is rendered (#1196)

Author: sliverc

Diff for: CHANGELOG.md

@@ -19,6 +19,8 @@ any parts of the framework not mentioned in the documentation should generally b
 
 * Fixed OpenAPI schema generation for `Serializer` when used inside another `Serializer` or as a child of `ListField`.
 * `ModelSerializer` fields are now returned in the same order than DRF
+* Avoided that an empty attributes dict is rendered in case serializer does not
+  provide any attribute fields.
 
 ### Removed
 

Diff for: example/tests/unit/test_renderers.py

@@ -126,7 +126,7 @@ class WriteonlyTestSerializer(serializers.ModelSerializer):
 
         class Meta:
             model = Entry
-            fields = ("comments", "rating")
+            fields = ("headline", "comments", "rating")
 
     class WriteOnlyDummyTestViewSet(views.ReadOnlyModelViewSet):
         queryset = Entry.objects.all()
@@ -136,6 +136,7 @@ class WriteOnlyDummyTestViewSet(views.ReadOnlyModelViewSet):
     result = json.loads(rendered.decode())
 
     assert "rating" not in result["data"]["attributes"]
+    assert "headline" in result["data"]["attributes"]
     assert "relationships" not in result["data"]
 
 
@@ -153,6 +154,7 @@ class EmptyRelationshipViewSet(views.ReadOnlyModelViewSet):
 
     rendered = render_dummy_test_serialized_view(EmptyRelationshipViewSet, Author())
     result = json.loads(rendered.decode())
+    assert "attributes" not in result["data"]
     assert "relationships" in result["data"]
     assert "bio" in result["data"]["relationships"]
     assert result["data"]["relationships"]["bio"] == {"data": None}

Diff for: rest_framework_json_api/renderers.py

@@ -452,8 +452,10 @@ def build_json_resource_obj(
         resource_data = {
             "type": resource_name,
             "id": utils.get_resource_id(resource_instance, resource),
-            "attributes": cls.extract_attributes(fields, resource),
         }
+        attributes = cls.extract_attributes(fields, resource)
+        if attributes:
+            resource_data["attributes"] = attributes
         relationships = cls.extract_relationships(fields, resource, resource_instance)
         if relationships:
             resource_data["relationships"] = relationships