KeyError: Got KeyError when attempting to get a value for a simple CharField declared in the Meta fields on serializer

[AvaStancu]

Calling get for ContractListAPIView fetches the results correctly but rendering them with the DRF templates raises a KeyError (for reference further on, 'name' is a models.CharField on the Contract model). I have seen this error before on DRF rendering since moving to python3.8 but back then it was related to a field inheriting from PrimaryKeyRelatedField so I said maybe that one was messing something up. But here it's just a simple model CharField. Is this a known issue? Does it have a solution?

class ContractSerializer(serializers.ModelSerializer):
    [...nothing related to name here]
    class Meta:
        model = Contract
        fields = [
            "id",
            "name",
            [...]
        ]
        
class ContractPaginatedResponseSerializer(serializers.Serializer):
    count = serializers.IntegerField()
    results = ContractSerializer(many=True)
    
class ContractListAPIView(generics.ListAPIView):
        serializer_class = ContractSerializer
        pagination_class = ContractPagination
        
        def get(self, request, *args, **kwargs):
            contracts = self.get_queryset()
            page = self.paginate_queryset_if_page_param(
            contracts
        )
            return Response(  # this is rest_framework.response's Response model
            ContractPaginatedResponseSerializer(
                {"count": contracts.count(), "results": page}
            ).data
        )
        

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.8/site-packages/django/core/handlers/base.py", line 204, in _get_response
    response = response.render()
  File "/usr/local/lib/python3.8/site-packages/django/template/response.py", line 105, in render
    self.content = self.rendered_content
  File "/usr/local/lib/python3.8/site-packages/rest_framework/response.py", line 70, in rendered_content
    ret = renderer.render(self.data, accepted_media_type, context)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/renderers.py", line 724, in render
    context = self.get_context(data, accepted_media_type, renderer_context)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/renderers.py", line 657, in get_context
    raw_data_patch_form = self.get_raw_data_form(data, view, 'PATCH', request)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/renderers.py", line 563, in get_raw_data_form
    data = serializer.data.copy()
  File "/usr/local/lib/python3.8/site-packages/rest_framework/serializers.py", line 548, in data
    ret = super().data
  File "/usr/local/lib/python3.8/site-packages/rest_framework/serializers.py", line 246, in data
    self._data = self.to_representation(self.instance)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/serializers.py", line 502, in to_representation
    attribute = field.get_attribute(instance)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/fields.py", line 490, in get_attribute
    raise type(exc)(msg)
KeyError: "Got KeyError when attempting to get a value for field `name` on serializer `ContractSerializer`.\nThe serializer field might be named incorrectly and not match any attribute or key on the `dict` instance.\nOriginal exception text was: 'name'."

[hashlash]

Could you please provide your ContractPagination and paginate_queryset_if_page_param implementation? Have you tried using the built-in pagination class?

[hashlash]

@AvaStancu

I've tried to reproduce your bug but it works fine. Can you take a look at the repo and see if anything is different from your case? Perhaps it's a bug from the old DRF version, have you tried to update your dependencies?

[AvaStancu]

Sure, ContractPagination is inheriting from DRF's PageNumberPagination

class ContractPagination(PageNumberPagination):
    page_size = 10
    page_size_query_param = "page_size"
    max_page_size = 50

def paginate_queryset_if_page_param(self, queryset):
    if self.pagination_class.page_query_param in self.request.query_params.keys():
        return self.paginate_queryset(queryset)

and paginate_queryset returns the self.paginator.paginate_queryset(queryset, self.request, view=self) self being an PaginationHandlerMixin that has an instance of the paginator and does this paginate_queryset if a page param exists.

[shamspias]

Is it fixed yet ?