How to show query parameter options in Django REST Framework – Swagger

I found the rest framework swagger docs.
so we can write the parameter type(interger, char), response, etc.

the tripple --- is necessary.

@api_view(["POST"])
def foo_view(request):
    """
    Your docs
    ---
    # YAML (must be separated by `---`)

    type:
      name:
        required: true
        type: string
      url:
        required: false
        type: url
      created_at:
        required: true
        type: string
        format: date-time

    serializer: .serializers.FooSerializer
    omit_serializer: false

    parameters_strategy: merge
    omit_parameters:
        - path
    parameters:
        - name: name
          description: Foobar long description goes here
          required: true
          type: string
          paramType: form
        - name: other_foo
          paramType: query
        - name: other_bar
          paramType: query
        - name: avatar
          type: file

    responseMessages:
        - code: 401
          message: Not authenticated
    """

How about the situation we use the mixins class such as ModelViewSets.
Do we need to define the list function just to add the docs?
— No

We can do like this:

class ArticleViewSet(viewsets.ModelViewSet):

    """
    Articles.
    ---
    list:    #<--- here!!
        parameters:
            - name: name
              description: article title
    get_price:
        omit_serializer: true

    """

    @list_route(methods=['get'])
    def get_price(self, request):
        pass

New swagger

from rest_framework.filters import BaseFilterBackend
import coreapi

class SimpleFilterBackend(BaseFilterBackend):
    def get_schema_fields(self, view):
        return [coreapi.Field(
            name='query',
            location='query',
            required=False,
            type='string'
        )]

class MyViewSet(viewsets.ViewSet):
    filter_backends = (SimpleFilterBackend,)

    def list(self, request, *args, **kwargs):
        # print(request.GET.get('query'))  # Use the query param in your view
        return Response({'hello': 'world'}, status.HTTP_200_OK)

Disclaimer: I am using django_filters, so results may vary. django_filters uses the param filter_fields in the DRF ViewSet, which may be different than not using django_filters.

I took inspiration from this thread and overrode the get_schema_fields() method in the filtering backend in the following way.

settings.py

REST_FRAMEWORK = {
    ...
    'DEFAULT_FILTER_BACKENDS': ('location.of.custom_backend.CustomDjangoFilterBackend')
    ...
}

custom_backend.py

import coreapi
import coreschema
from django_filters.rest_framework import DjangoFilterBackend


class CustomDjangoFilterBackend(DjangoFilterBackend):
    """
    Overrides get_schema_fields() to show filter_fields in Swagger.
    """

    def get_schema_fields(self, view):
        assert (
            coreapi is not None
        ), "coreapi must be installed to use `get_schema_fields()`"
        assert (
            coreschema is not None
        ), "coreschema must be installed to use `get_schema_fields()`"

        # append filter fields to existing fields
        fields = super().get_schema_fields(view)
        if hasattr(view, "filter_fields"):
            fields += view.filter_fields

        return [
            coreapi.Field(
                name=field,
                location='query',
                required=False,
                type='string',
            ) for field in fields
        ]

Elaborating on the answers above from @vadimchin – here is a working example.

# requirements.txt

djangorestframework==3.9.3
django-rest-swagger==2.2.0
django==2.2.1
coreapi==2.3.3

I am using Viewsets in my application. I had to implement filter_queryset(self, request, queryset, view) as suggested by @jarussi.

# models.py

from django.db import models 

class Recording(models.Model):
    _id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=511)

# serializers.py

from models import Recording
from rest_framework import serializers

class RecordingSerializer(serializers.ModelSerializer):
    class Meta:
        model = Recording
        fields = '__all__'

# views.py

from rest_framework import viewsets
from filters import NameFilterBackend
from serializers import RecordingSerializer

class RecordingViewSet(viewsets.ModelViewSet):
    serializer_class = RecordingSerializer
    queryset = Recording.objects.all()
    filter_backends = (NameFilterBackend,)

# filters.py 

from rest_framework.filters import BaseFilterBackend
import coreapi

class NameFilterBackend(BaseFilterBackend):
    def get_schema_fields(self, view):
        return [coreapi.Field(
            name='name',
            location='query',
            required=False,
            type='string',
            description='name of recording'
        )]

    def filter_queryset(self, request, queryset, view):
        try:
            n = request.query_params['name']
            queryset = queryset.filter(name=n)
        except KeyError:
            # no query parameters
            pass
        return queryset

Please refer this github issue which solves the problem.

Working with openapi (and not coreapi), the “simplest” way I found is from this core dev comment:

from rest_framework.schemas.openapi import AutoSchema


class CustomSchema(AutoSchema):
    def get_operation(self, path, method):
        op = super().get_operation(path, method)
        op['parameters'].append({
            "name": "foo",
            "in": "query",
            "required": True,
            "description": "What foo does...",
            'schema': {'type': 'string'}
        })
        return op


class MyViewSet(ModelViewSet):
    schema = CustomSchema()

    def get_queryset(self):
        foo = self.request.query_params.get("foo")
        if foo:
            self.queryset = self.queryset.filter(foo=foo)
        return self.queryset

If the query parameters are used in a filter backend, adding a get_schema_operation_parameters method is the simplest solution:

class SimpleFilterBackend(BaseFilterBackend):
    def filter_queryset(self, request, queryset, view):
        foo = request.query_params.get("foo")
        if foo:
            queryset = queryset.filter(foo=foo)
        return queryset

    def get_schema_operation_parameters(self, view):
        return [{
            "name": "foo",
            "in": "query",
            "required": True,
            "description": "What foo does...",
            "schema": {"type": "string"}
        }]

class MyViewSet(ModelViewSet):
    filter_backends = [SimpleFilterBackend]

For anyone stumbling upon this later, I pieced together a few solutions and came up with this:

This is using the new openapi instead of coreapi.

I subclassed AutoSchema to accept a dictionary keyed on action name and mapping to the OpenApi Operation Parameter object spec. These params get appended to the operation.

from rest_framework.schemas.openapi import AutoSchema

class ParameterSchema(AutoSchema):
    def __init__(self, **kwargs):
        self.parameters = kwargs.pop("parameters")
        super().__init__(**kwargs)

    def get_operation(self, path, method):
        op = super().get_operation(path, method)
        method_name = getattr(self.view, "action", method.lower())
        action_parameters = self.parameters.get(method_name, [])
        for param in action_parameters:
            op["parameters"].append(param)
        return op


class MyViewSet(viewsets.ModelViewSet):
    schema = ParameterSchema(
        parameters={
            "list": [
                {
                    "name": "my-param",
                    "in": "query",
                    "required": False,
                    "description": "Description on the param",
                    "schema": {"type": "boolean", "default": False},
                }
            ]
        }
    )