Django rest_framework custom error message - django

Question

I have a API endpoint where it will do input validation using rest_framework's serializer.is_valid() where it will return custom error message and response.
serializer = FormSerializer(data=data)
if not serializer.is_valid(raise_exception=False):
return Response({"Failure": "Error"}, status=status.HTTP_400_BAD_REQUEST)
Is it possible to populate validation errors without using the generic response provided by raise_exception=True? I am trying to avoid using the generic response as it will display all the validation errors if there are more than one error.
The response will be something like
return Response(
{
"Failure": "Error",
"Error_list": {"field1": "This field is required"}
},
status=status.HTTP_400_BAD_REQUEST
)

Answer 1

Create a Custom Exception class as,
from rest_framework.exceptions import PermissionDenied
from rest_framework import status
class MyCustomExcpetion(PermissionDenied):
status_code = status.HTTP_400_BAD_REQUEST
default_detail = "Custom Exception Message"
default_code = 'invalid'
def __init__(self, detail, status_code=None):
self.detail = detail
if status_code is not None:
self.status_code = status_code
Why I'm inherrited from PermissionDenied exception class ??
see this SO post -- Why DRF ValidationError always returns 400
Then in your serializer, raise exceptions as,
class SampleSerializer(serializers.ModelSerializer):
class Meta:
fields = '__all__'
model = SampleModel
def validate_age(self, age): # field level validation
if age > 10:
raise MyCustomExcpetion(detail={"Failure": "error"}, status_code=status.HTTP_400_BAD_REQUEST)
return age
def validate(self, attrs): # object level validation
if some_condition:
raise MyCustomExcpetion(detail={"your": "exception", "some_other": "key"}, status_code=status.HTTP_410_GONE)
return attrs
age and name are two fields of SampleModel class
Response will be like this
By using this method,
1. You can customize the JSON Response
2. You can return any status codes
3. You don't need to pass True in serializer.is_valid() method (This is not reccomended)

Answer 2

A simple way is to use one of the exception messages, eg NotFound. See docs
# views.py
from rest_framework.exceptions import NotFound
class myview(viewsets.ModelViewSet):
def perform_create(self, serializer):
raise NotFound("My text here")
That will return a 404 and change the response to your text
HTTP 404 Not Found
Allow: GET, POST, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept
{
"detail": "my text here"
}

Answer 3

You can write custom error handler:
from rest_framework.views import exception_handler
def custom_exception_handler(exc, context):
response = exception_handler(exc, context)
if response is not None:
response.data['Failure'] = 'Error'
return response