Integration with drf-rw-serializers

[luzfcb]

Describe the bug
Hello, first of all, thanks for your work. This library is being very useful for one of the projects I'm working on.

One of the projects I work on, we make extensive use of drf-rw-serializers.

This means that serializer_class is not defined in the Views, and instead, write_serializer_class and read_serializer_class are defined.

All view classes provided by drf-rw-serializers inherit from drf-rw-serializers GenericAPIView class https://github.com/vintasoftware/drf-rw-serializers/blob/master/drf_rw_serializers/generics.py#L8-L71

I'm trying to get the documentation generated correctly, but I haven't been able to succeed yet.

The generated schema does not include any information provided by serializers:

  /api/mymodel/:
    post:
      operationId: mymodel_create
      description: ''
      tags:
      - core
      security:
      - cookieAuth: []
      - basicAuth: []
      responses:
        '201':
          description: No response body
  /api/mymodel/{id}/:
    get:
      operationId: mymodel_retrieve
      description: ''
      parameters:
      - in: path
        name: id
        schema:
          type: integer
        required: true
      tags:
      - core
      security:
      - cookieAuth: []
      - basicAuth: []
      responses:
        '200':
          description: No response body

Below is the minimum code to reproduce the problem.

To Reproduce

from rest_framework.permissions import IsAdminUser
from rest_framework import parsers
from drf_rw_serializers.viewsets import ModelViewSet as ModelRWViewSet
from drf_spectacular.utils import extend_schema, extend_schema_view

from .models import MyModel
from .serializers import MyModelUploadSerializer, MyModelSerializer

@extend_schema_view(
    post=extend_schema(
        description="POST method description here",
        request=MyModelUploadSerializer,
        responses={
            201: MyModelSerializer
        }
    ),
    get=extend_schema(
        description="GET method description here",
        responses={
            200: MyModelSerializer
        }
    )
)
class MyAPIView(ModelRWViewSet):
    queryset = MyModel.objects.order_by('-created').all()
    write_serializer_class = MyModelUploadSerializer
    read_serializer_class = MyModelSerializer
    permission_classes = [IsAdminUser]
    parser_classes = [parsers.MultiPartParser]

urls.py

from django.urls import path
from .api_views import MyAPIView

urlpatterns = [
    path('api/mymodel/', view=MyAPIView.as_view({'post': 'create'}),
         name='mymodel-upload'
         ),
    path('api/mymodel/<int:pk>/', view=MyAPIView.as_view({'get': 'retrieve'}),
         name='mymodel-detail'
         ),
]

Expected behavior

I would hope to get some hint on how to implement a generic way to make drf-spectacular understand the structure of a view that inherits from drf-rw-serializers GenericAPIView class and from there, be able to use write_serializer_class and read_serializer_class instead of just serializer_class to generate the OpenAPI schema.

[tfranzel]

hi @luzfcb,

that's a pretty neat library i never heard about. nice and very useful. regarding your schema not changing

https://drf-spectacular.readthedocs.io/en/latest/faq.html#using-extend-schema-on-apiview-has-no-effect

so i'm pretty sure you used the wrong method names for @extend_schema_view. for viewsets it must be create and list/retrieve not post etc. for a APIView it would be correct like that.

if you use this a lot i would recommend having a patched AutoSchema that accounts for this lib. something like

class CustomSchema(AutoSchema):

    def get_request_serializer(self):
        """ override this for custom behaviour """
        if isinstance(self.view, drf_rw_serializers.GenericAPIView):
             return view.get_write_serializer_class()()
        return self._get_serializer()

    def get_response_serializers(self):
        """ override this for custom behaviour """
        if isinstance(self.view, drf_rw_serializers.GenericAPIView):
             return view.get_read_serializer_class()()
        return self._get_serializer()

this would probably need some refinement but should point you in the right direction. don't forget to set this AutoSchema in the settings.

[tfranzel]

this does not really fit into the core but we can add a blueprint to the docs and link in on the global Readme if you care to do a PR

[luzfcb]

@tfranzel thanks for pointing out my error in using the wrong method names with viewsets... my initial implementation didn't use viewsets and I hadn't read the FAQ documentation before. Sorry about that.

Thanks for the tip to customize AutoSchema, it worked almost without changes.

from drf_spectacular.openapi import AutoSchema
from drf_rw_serializers.generics import GenericAPIView as RWGenericAPIView


class CustomAutoSchema(AutoSchema):
    def get_request_serializer(self):
        if isinstance(self.view, RWGenericAPIView):
            return self.view.get_write_serializer_class()()
        return self._get_serializer()

    def get_response_serializers(self):
        if isinstance(self.view, RWGenericAPIView):
            return self.view.get_read_serializer_class()()
        return self._get_serializer()

On your settings.py:

REST_FRAMEWORK = {
    # ...
    'DEFAULT_SCHEMA_CLASS': 'path.to.your.openapi.CustomAutoSchema',
}

I plan to create a pull-request to include this example in the documentation

[tfranzel]

awsome! it should probably go in here https://drf-spectacular.readthedocs.io/en/latest/blueprints.html with a link in the README. at least that is how i would imagine it.