How to return status code after getting db validation error in django-rest-framework?

Question

I have a test case that looks like this (the point being to prevent duplicate user profiles):

def test_create_duplicate_profile(self):
    new_user = models.User(
        username='bobjones',
        password=';alsdfkj;asoi'
    )
    new_user.save()
    client = APIClient()
    client.force_authenticate(new_user)
    response = client.post(
        path='/api/profiles/'
    )
    self.assertEqual(response.status_code, status.HTTP_201_CREATED)

    same_user = models.User.objects.get(
        username='bobjones'
    )
    response = client.post(
        path='/api/profiles/'
    )
    self.assertEqual(response.status_code, status.HTTP_409_CONFLICT)
    client.logout()

This results in an error (as well as failing test):

(.virtualenv) nbascoutingdotcom $ python manage.py test profiles
Creating test database for alias 'default'...
System check identified no issues (0 silenced).
E..
======================================================================
ERROR: test_create_duplicate_profile (profiles.tests.test_api.ProfilesAPITest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/evanzamir/nbascoutingdotcom/.virtualenv/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/Users/evanzamir/nbascoutingdotcom/.virtualenv/lib/python3.6/site-packages/django/db/backends/sqlite3/base.py", line 328, in execute
    return Database.Cursor.execute(self, query, params)
sqlite3.IntegrityError: UNIQUE constraint failed: profiles_profile.user_id

My model looks like this:

class Profile(TimestampModerated):
    id = models.BigAutoField(primary_key=True, db_column='id', null=False)
    uuid = models.UUIDField(db_index=True, default=uuid_lib.uuid4(), editable=False)
    user = models.OneToOneField('auth.User', on_delete=models.CASCADE, related_name='profiles', blank=False,
                                unique=True)
    bio = models.CharField(max_length=140, blank=True, null=True)
    media_url = models.URLField(blank=True, null=True)
    dob = models.DateField(blank=True, null=True)

    class Meta:
        verbose_name_plural = "profiles"

Here is the serializer:

class ProfileSerializer(serializers.ModelSerializer):
    user = serializers.CharField(source='user.username', read_only=True,
                                 validators=[UniqueValidator(queryset=Profile.objects.all())])
    email = serializers.CharField(source='user.email', read_only=True)
    first = serializers.CharField(source='user.first_name', read_only=True)
    last = serializers.CharField(source='user.last_name', read_only=True)
    last_login = serializers.DateTimeField(source='user.last_login', read_only=True)
    date_joined = serializers.DateTimeField(source='user.date_joined', read_only=True)

    class Meta:
        model = Profile
        fields = ('id', 'created', 'moderation_code', 'user', 'updated', 'uuid', 'bio', 'email',
                  'first', 'last', 'last_login', 'media_url', 'dob', 'date_joined')

Here is my ViewSet:

class ProfileViewSet(viewsets.ModelViewSet):
    """
    This viewsetomatically provides `list`, `create`, `retrieve`,
    `update` and `destroy` actions.

    """
    queryset = Profile.objects.all()
    serializer_class = ProfileSerializer
    authentication_classes = (SessionAuthentication,)
    permission_classes = (permissions.AllowAny, IsOwnerOrReadOnly)
    lookup_field = 'user'

    def perform_create(self, serializer):
        serializer.save(user=self.request.user)

I would like to be able to send back a valid HTTP status code (HTTP_40X_), but I can't seem to be able to hook into the validation error. I tried putting some code in the perform_create method to raise a ValidationError, but that didn't work for me. Any suggestions?

Could you check in the viewset if a Profile for self.request.user already exists and return early with your error code of choice? — perfect5th
– perfect5th, Commented Jul 23, 2017 at 1:00

eager_learner · Accepted Answer · 2018-06-11 08:30:16Z

1

You'd have to hook into ModelViewSet.create(...) where the actual response is created and returned:

from rest_framework import status
from rest_framework.response import Response


def create(self, request, *args, **kwargs):
    try:
        return super(ProfileViewSet, self).create(request, *args, **kwargs):
    except IntegrityError:
        return Response(status=status.HTTP_409_CONFLICT)

For a more general project-wide approach, you might also read the drf docs on custom exception handling.

edited Jun 11, 2018 at 8:30

eager_learner

1541 silver badge9 bronze badges

answered Jul 23, 2017 at 1:20

user2390182

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