Support annotating a `PATCH` `@action` with `@extend_schema` to use `PatchedTRequest`

[johnthagen]

I have an @action of the form:

    @action(
        methods=[HTTPMethod.PATCH],
        detail=False,
        url_path="bulk-partial-update",
    )
    def bulk_partial_update(self, request: Request) -> Response:
        ...

And a ViewSet of the form:

@extend_schema_view(
    bulk_partial_update=extend_schema(
        request=TSerializer(many=True), responses=TSerializer(many=True)
    ),
)
class TViewSet(ModelViewSet):
    queryset = T.objects.all()
    ...

I was hoping that because the @action was tagged as HTTPMethod.PATCH that drf-spectacular would automatically use the PatchedTRequest form of the generated T for the request side of the API since PATCH is used in HTTP for partial updates.

But when I looked at the generated OpenAPI spec, I found it looked like:

  /T/bulk-partial-update/:
    patch:
      operationId: t_bulk_partial_update_partial_update
      requestBody:
        content:
          application/json:
            schema:
              type: array
              items:
                $ref: '#/components/schemas/TRequest'
        required: true
      responses:
        '200':
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/T'
          description: ''

Specifically I was hoping that requestBody would use PatchedTRequest.

[johnthagen]

This code seems relevant to this issue

drf-spectacular/drf_spectacular/plumbing.py

Lines 170 to 176 in a79bc5d

	def is_patched_serializer(serializer, direction) -> bool:
	return bool(
	spectacular_settings.COMPONENT_SPLIT_PATCH
	and getattr(serializer, 'partial', None)
	and not getattr(serializer, 'read_only', None)
	and not (spectacular_settings.COMPONENT_SPLIT_REQUEST and direction == 'response')
	)

[johnthagen]

I was able to manually add partial=True to work around this.

@extend_schema_view(
    bulk_partial_update=extend_schema(
        request=TSerializer(many=True, partial=True), responses=TSerializer(many=True)
    ),
)

[johnthagen]

So the only issue I have remaining is that for bulk partial updates, I need to have the required id present, but all other fields marked optional. partial=True solves the part of making all fields optional, but is there any clean way to also describe "even for this request, the id field must exist"?

As an example of what the partial update data looks like:

[
  {"id": 1, "name": "fred"},
  {"id": 2, "age": 10}
]