AttributeError: 'ListSerializer' object has no attribute 'fields'

[srtab]

Hi,
I'm using a ListSerializer in my views and when I try to load do openapi, just raise the following exception:

...
File "/usr/local/lib/python3.6/site-packages/drf_spectacular/views.py", line 34, in get
  public=spectacular_settings.SERVE_PUBLIC
File "/usr/local/lib/python3.6/site-packages/drf_spectacular/openapi.py", line 107, in get_schema
  paths=self.parse(None if public else request),
File "/usr/local/lib/python3.6/site-packages/drf_spectacular/openapi.py", line 87, in parse
  operation = view.schema.get_operation(path, method, self.registry)
File "/usr/local/lib/python3.6/site-packages/drf_spectacular/openapi.py", line 136, in get_operation
  request_body = self._get_request_body(path, method)
File "/usr/local/lib/python3.6/site-packages/drf_spectacular/openapi.py", line 743, in _get_request_body
  component = self.resolve_serializer(method, serializer)
File "/usr/local/lib/python3.6/site-packages/drf_spectacular/openapi.py", line 867, in resolve_serializer
  component.schema = self._map_serializer(method, serializer)
File "/usr/local/lib/python3.6/site-packages/drf_spectacular/openapi.py", line 605, in _map_serializer
  return self._map_basic_serializer(method, serializer)
File "/usr/local/lib/python3.6/site-packages/drf_spectacular/openapi.py", line 611, in _map_basic_serializer
  for field in serializer.fields.values():
AttributeError: 'ListSerializer' object has no attribute 'fields'

ListSerializer doesn't have fields attribute, but can be extracted from child attribute. Do you think that makes sense drf-spectacular to support this kind of serializers too?

[tfranzel]

Hi @srtab, thats for raising that issue. spectacular should never bail with an exception so this is a bug.

actually ListSerializers are usually auto-substituted by using field = XXXSerializer(many=True), which we support. I never used it manually.

could you please provide a small snipped on how you use ListSerializer, to maybe incorporate that use case?

[srtab]

I'm using it to make bulk updates, here is an simple example:

serializers.py

from rest_framework import serializers

from .models import Step


class StepSerializer(serializers.ModelSerializer):
    class Meta:
        model = Step
        fields = ("pk", "position")
        extra_kwargs = {"pk": {"read_only": False}}


class StepListSerializer(serializers.ListSerializer):
    child = StepSerializer()

    def update(self, instance, validated_data):
        ...

views.py

from rest_framework.generics import GenericAPIView

from .models import Step
from .serializers import StepListSerializer

class StepUpdateAPIView(GenericAPIView):
    model = Step
    serializer_class = StepListSerializer

    def post(self, request, *args, **kwargs):
        serializer = self.get_serializer(self.get_queryset(), data=request.data)
        serializer.is_valid(raise_exception=True)
        serializer.save()
        return Response(serializer.data)

[tfranzel]

@srtab that looks like reasonable usage. i fixed the exception and added ListSerializer handling for explicit usage.
the way the list is expanded (and the operation_id) is opinionated, but in accordance with the implicit usage. i hope this solves your problem.

[srtab]

@tfranzel That's perfect! Thanks for the fast response!
And Congrats for the fantastic app!

[tfranzel]

you're welcome and thank you!