custom_exception_handdler.py

from rest_framework.views import exception_handler
from rest_framework import status
from django.http import Http404


def custom_exception_handler(exc, context):
    """
    This function will handle errors that are returned by
    the different views.
    The `handlers` dictionary will map
    each exception name to the function that should handle it.
    Each function should return a response with a message
    and the actual error.
    """

    # We Call REST framework's default exception handler first
    response = exception_handler(exc, context)
    handlers = {
        'ValidationError': _handle_generic_error,
        'Http404': _handle_generic_error,
        'PermissionDenied': _handle_generic_error,
        'NotAuthenticated': _handle_authentication_error
    }

    exception_class = exc.__class__.__name__
    # Now we add the HTTP status code to the response when its in the context
    # of the LoginAPIVIew.
    if response is not None:
        # Raising a NotAuthenticatedError should send a 401 response status
        # code, however due to the Authentication scheme used by our
        # application it raises 403 instead. This calls for the need to
        # write a custom exception handler and make it send a 401 in the
        # context of login
        response = _handle_generic_error(exc, context, response)
        response.data['status_code'] = response.status_code

        if "AuthUserAPIView" in str(context['view']) and exc.status_code == 401:
            response.status_code = status.HTTP_200_OK
            response.data = {'is_logged_in': False}
            return response

    if exception_class in handlers:
        return handlers[exception_class](exc, context, response)

    return response


def _handle_generic_error(exc, context, response):
    # We take the response generated by DRF and wrap it in the `errors` key
    return response


def _handle_authentication_error(exc, context, response):
    """If users are not logged in, we return this custom response"""
    response.data = {
        'error': 'Please log in to proceed.'
    }
    response.data['status_code'] = response.status_code

    return response