OPTIONS does not use action specific serializers

[EmCeeEs]

Assume an app that manages information about countries:

from django.db import models
from rest_framework import viewsets, serializers, routers


class Country(models.Model):
    name = models.CharField(max_length=100)
    population = models.PositiveIntegerField()


class CountrySerializer(serializers.ModelSerializer):
    class Meta:
        model = Country
        fields = "__all__"


class CountryCreateSerializer(serializers.ModelSerializer):
    class Meta:
        model = Country
        fields = ("name",)


class CountryViewSet(viewsets.ModelViewSet):
    queryset = Country.objects.all()
    serializer_class = CountrySerializer

    def get_serializer_class(self):
        if self.action == "create":
            return CountryCreateSerializer
        return super().get_serializer_class()


router = routers.DefaultRouter()
router.register(r"country", CountryViewSet)


urlpatterns = router.urls

OPTIONS /country/

Expected Behavior

POST action reflects CountryCreateSerializer fields:

HTTP 200 OK
Allow: GET, POST, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "name": "Country List",
    "description": "",
    "renders": [
        "application/json",
        "text/html"
    ],
    "parses": [
        "application/json",
        "application/x-www-form-urlencoded",
        "multipart/form-data"
    ],
    "actions": {
        "POST": {
            "name": {
                "type": "string",
                "required": true,
                "read_only": false,
                "label": "Name",
                "max_length": 100
            },
        }
    }
}

Actual Behavior

POST action reflects CountrySerializer fields:

HTTP 200 OK
Allow: GET, POST, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "name": "Country List",
    "description": "",
    "renders": [
        "application/json",
        "text/html"
    ],
    "parses": [
        "application/json",
        "application/x-www-form-urlencoded",
        "multipart/form-data"
    ],
    "actions": {
        "POST": {
            "id": {
                "type": "integer",
                "required": false,
                "read_only": true,
                "label": "ID"
            },
            "name": {
                "type": "string",
                "required": true,
                "read_only": false,
                "label": "Name",
                "max_length": 100
            },
            "population": {
                "type": "integer",
                "required": true,
                "read_only": false,
                "label": "Population",
                "min_value": 0,
                "max_value": 2147483647
            }
        }
    }
}

Explanation / Resolution

SimpleMetadata.determine_actions should take the action specific serializers into account.

Current workaround

class DynamicSerializerMetadata(SimpleMetadata):
    def determine_actions(self, request, view):
        actions = {}
        for method in {"PUT", "POST"} & set(view.allowed_methods):
            view.request = clone_request(request, method)
            try:
                # Test global permissions
                if hasattr(view, "check_permissions"):
                    view.check_permissions(view.request)
                # Test object permissions
                if method == "PUT" and hasattr(view, "get_object"):
                    view.get_object()
            except (exceptions.APIException, PermissionDenied, Http404):
                pass
            else:
                # If user has appropriate permissions for the view, include
                # appropriate metadata about the fields that should be supplied.

                view.action =  view.action_map.get(method.lower())  # <----- SET TO CORRECT ACTION BEFORE CALLING get_serializer
                serializer = view.get_serializer()
                view.action = "metadata" # <------ RESTORE
                actions[method] = self.get_serializer_info(serializer)
            finally:
                view.request = request
        
        return actions