OPTIONS fields type doesn't return "multiple choice" for generic ManyToMany fields on ModelSerilalizer subclasses

[ugurunver]

Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• I have reduced the issue to the simplest possible case.
• I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Steps to reproduce

Python 2 virtual environment:

# requirements
Django==1.9.5
argparse==1.2.1
djangorestframework==3.3.3  # i checked metadata.py on master already, it is same
wsgiref==0.1.2

# myapp.models
from django.db import models


class SampleSubModel(models.Model):
    name = models.CharField(max_length=100)


class SampleModel(models.Model):
    subs = models.ManyToManyField(SampleSubModel)

# myapp.serializers
from rest_framework import serializers
from myapp import models

class SampleModelSerializer(serializers.ModelSerializer):
     class Meta:
        model = models.SampleModel

# myapp.views
from rest_framework import viewsets
from myapp import models
from myapp import serializers

class SampleViewset(viewsets.ModelViewSet):
    serializer_class = serializers.SampleModelSerializer
    queryset = models.SampleModel.objects.all()

    def post(self):
        # i don't know why this is necessary, but tests need this
        pass

# myapp.tests

from django.test import TestCase

from rest_framework.request import Request
from rest_framework.test import APIRequestFactory

from rest_framework import serializers
from rest_framework.metadata import SimpleMetadata

from myapp.views import SampleViewset


request = Request(APIRequestFactory().options('/?format=api'))

class TestSampleOptions(TestCase):

    def test_options(self):

        view = SampleViewset.as_view({'options': 'options'})
        response = view(request)
        subs_type = response.data["actions"]["POST"]["subs"]["type"]
        self.assertEqual(subs_type, "multiple choice")  # fails because returns "field"

    def test_options_with_custom_metadata(self):
        class CustomMetadata(SimpleMetadata):
            custom_label_lookup = SimpleMetadata.label_lookup
            custom_label_lookup[serializers.ManyRelatedField] = 'multiple choice'
            label_lookup = custom_label_lookup

        class NewSampleViewset(SampleViewset):
            metadata_class = CustomMetadata

        view = NewSampleViewset.as_view({'options': 'options'})
        response = view(request)
        subs_type = response.data["actions"]["POST"]["subs"]["type"]
        self.assertEqual(subs_type, "multiple choice")

Expected behavior

ManyToMany fields must be represented as multiple selectbox fields on frontend, so field type should be "multiple choice", and i guess you missed this because you are rendering data on backend in BrowsableApiRenderer and you didn't notice what we need on frontend.

(venv)ugur@pcpc:~/workspace/test/drftest$ ./manage.py  test myapp.tests.TestSampleOptions.test_options_with_custom_metadata
Creating test database for alias 'default'...
.
----------------------------------------------------------------------
Ran 1 test in 0.005s

OK
Destroying test database for alias 'default'...

Actual behavior

It returns "field" for manytomany fields because SimpleMetadata.label_lookup doesn't handle serializers.ManyRelatedField

(venv)ugur@pcpc:~/workspace/test/drftest$ ./manage.py  test myapp.tests.TestSampleOptions.test_options
Creating test database for alias 'default'...
F
======================================================================
FAIL: test_options (myapp.tests.TestSampleOptions)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/ugur/workspace/test/drftest/myapp/tests.py", line 22, in test_options
    self.assertEqual(subs_type, "multiple choice")  # fails because returns "field"
AssertionError: u'field' != 'multiple choice'

----------------------------------------------------------------------
Ran 1 test in 0.005s

FAILED (failures=1)
Destroying test database for alias 'default'...

[tomchristie]

The AssertionError here is noted and sounds like it needs to be fixed, tho note that we probably shouldn't be displaying relationship choices in the OPTIONS response (although we currently do), as it opens up too much information to the user that the developer may not have intended to, so any fix for this should resolve the error, but not present a complete list of choices.

[tomchristie]

Closing as per #4160.