Remove the POLYMORPHIC_ANCESTOR code

Author: leo-naeka

docs/usage.md

@@ -427,19 +427,6 @@ field_name_mapping = {
 
 ### Working with polymorphic resources
 
-#### Extraction of the polymorphic type
-
-This package can defer the resolution of the type of polymorphic models instances to retrieve the appropriate type.
-However, most models are not polymorphic and for performance reasons this is only done if the underlying model is a subclass of a polymorphic model.
-
-Polymorphic ancestors must be defined on settings like this:
-
-```python
-JSON_API_POLYMORPHIC_ANCESTORS = (
-    'polymorphic.models.PolymorphicModel',
-)
-```
-
 #### Writing polymorphic resources
 
 A polymorphic endpoint can be setup if associated with a polymorphic serializer.

example/settings/test.py

@@ -15,6 +15,3 @@
 REST_FRAMEWORK.update({
     'PAGE_SIZE': 1,
 })
-JSON_API_POLYMORPHIC_ANCESTORS = (
-    'polymorphic.models.PolymorphicModel',
-)

rest_framework_json_api/renderers.py

@@ -362,7 +362,8 @@ def extract_included(cls, fields, resource, resource_instance, included_resource
                                 serializer_fields,
                                 serializer_resource,
                                 nested_resource_instance,
-                                resource_type
+                                resource_type,
+                                getattr(serializer, '_poly_force_type_resolution', False)
                             )
                         )
                         included_data.extend(
@@ -384,7 +385,8 @@ def extract_included(cls, fields, resource, resource_instance, included_resource
                     included_data.append(
                         cls.build_json_resource_obj(
                             serializer_fields, serializer_data,
-                            relation_instance, relation_type)
+                            relation_instance, relation_type,
+                            getattr(field, '_poly_force_type_resolution', False))
                     )
                     included_data.extend(
                         cls.extract_included(
@@ -426,9 +428,10 @@ def extract_root_meta(cls, serializer, resource):
         return data
 
     @classmethod
-    def build_json_resource_obj(cls, fields, resource, resource_instance, resource_name):
+    def build_json_resource_obj(cls, fields, resource, resource_instance, resource_name,
+                                force_type_resolution=False):
         # Determine type from the instance if the underlying model is polymorphic
-        if isinstance(resource_instance, utils.POLYMORPHIC_ANCESTORS):
+        if force_type_resolution:
             resource_name = utils.get_resource_type_from_instance(resource_instance)
         resource_data = [
             ('type', resource_name),
@@ -512,6 +515,9 @@ def render(self, data, accepted_media_type=None, renderer_context=None):
             # Get the serializer fields
             fields = utils.get_serializer_fields(serializer)
 
+            # Determine if resource name must be resolved on each instance (polymorphic serializer)
+            force_type_resolution = getattr(serializer, '_poly_force_type_resolution', False)
+
             # Extract root meta for any type of serializer
             json_api_meta.update(self.extract_root_meta(serializer, serializer_data))
 
@@ -523,7 +529,7 @@ def render(self, data, accepted_media_type=None, renderer_context=None):
                     resource_instance = serializer.instance[position]  # Get current instance
 
                     json_resource_obj = self.build_json_resource_obj(
-                        fields, resource, resource_instance, resource_name
+                        fields, resource, resource_instance, resource_name, force_type_resolution
                     )
                     meta = self.extract_meta(serializer, resource)
                     if meta:
@@ -538,7 +544,7 @@ def render(self, data, accepted_media_type=None, renderer_context=None):
             else:
                 resource_instance = serializer.instance
                 json_api_data = self.build_json_resource_obj(
-                    fields, serializer_data, resource_instance, resource_name
+                    fields, serializer_data, resource_instance, resource_name, force_type_resolution
                 )
 
                 meta = self.extract_meta(serializer, serializer_data)

rest_framework_json_api/serializers.py

@@ -198,6 +198,12 @@ def __new__(cls, name, bases, attrs):
         setattr(new_class, '_poly_serializer_model_map', serializer_to_model)
         setattr(new_class, '_poly_model_serializer_map', model_to_serializer)
         setattr(new_class, '_poly_type_serializer_map', type_to_serializer)
+        setattr(new_class, '_poly_force_type_resolution', True)
+
+        # Flag each linked polymorphic serializer to force type resolution based on instance
+        for serializer in polymorphic_serializers:
+            setattr(serializer, '_poly_force_type_resolution', True)
+
         return new_class
 
 

rest_framework_json_api/utils.py

@@ -52,11 +52,6 @@
         ReverseGenericRelatedObjectsDescriptor as ReverseGenericManyToOneDescriptor  # noqa: F401
     )
 
-POLYMORPHIC_ANCESTORS = ()
-for ancestor in getattr(settings, 'JSON_API_POLYMORPHIC_ANCESTORS', ()):
-    ancestor_class = import_class_from_dotted_path(ancestor)
-    POLYMORPHIC_ANCESTORS += (ancestor_class,)
-
 
 def get_resource_name(context, expand_polymorphic_types=False):
     """