allow implicit list expansion of PolymorphicProxySerializer #995

drf_spectacular/utils.py

@@ -79,17 +79,28 @@ def __init__(
             ],
             resource_type_field_name: Optional[str],
             many: Optional[bool] = None,
+            **kwargs
     ):
         self.component_name = component_name
         self.serializers = serializers
         self.resource_type_field_name = resource_type_field_name
         if self._many is False:  # type: ignore[attr-defined]
             set_override(self, 'many', False)
-        super().__init__()
+        # retain kwargs in context for potential anonymous re-init with many=True
+        kwargs.setdefault('context', {}).update({
+            'component_name': component_name,
+            'serializers': serializers,
+            'resource_type_field_name': resource_type_field_name
+        })
+        super().__init__(**kwargs)
 
     def __new__(cls, *args, **kwargs):
         many = kwargs.pop('many', None)
         if many is True:
+            context = kwargs.get('context', {})
+            for arg in ['component_name', 'serializers', 'resource_type_field_name']:
+                if arg in context:
+                    kwargs[arg] = context.pop(arg)  # re-apply retained args
             instance = cls.many_init(*args, **kwargs)
         else:
             instance = super().__new__(cls, *args, **kwargs)

tests/test_polymorphic.py

@@ -370,3 +370,31 @@ def list(self, request, *args, **kwargs):
             {'type': 'array', 'items': {'$ref': '#/components/schemas/NaturalPerson'}}
         ]
     }
+
+
+def test_polymorphic_implicit_many_through_list_method_decoration(no_warnings):
+    @extend_schema(responses=PolymorphicProxySerializer(**PROXY_SERIALIZER_PARAMS))
+    class XViewSet(viewsets.ReadOnlyModelViewSet):
+        queryset = LegalPerson2.objects.none()
+        serializer_class = LegalPersonSerializer
+
+    schema = generate_schema('/x', XViewSet)
+
+    assert get_response_schema(schema['paths']['/x/']['get']) == {
+        'items': {'$ref': '#/components/schemas/MetaPerson'}, 'type': 'array'
+    }
+    assert get_response_schema(schema['paths']['/x/{id}/']['get']) == {
+        '$ref': '#/components/schemas/MetaPerson'
+    }
+    assert schema['components']['schemas']['MetaPerson'] == {
+        'discriminator': {
+            'mapping': {
+                'legal': '#/components/schemas/LegalPerson',
+                'natural': '#/components/schemas/NaturalPerson'
+            },
+            'propertyName': 'type'
+        },
+        'oneOf': [
+            {'$ref': '#/components/schemas/LegalPerson'}, {'$ref': '#/components/schemas/NaturalPerson'}
+        ]
+    }