djnago_rest_framework_error_handler.md

Django rest framework error handler

This handler works only when you use django framework + django rest framework.

Requirements:

• django 2.0+
• django rest framework 3.8+

Instruction:

• Create error_handler.py in your project root folder and add source code there;
• Add information about error handler to rest framework settings;
• Add to the end of your project base urls file 404 handler.

Error handler code

from django.http import JsonResponse

from rest_framework import status
from rest_framework.views import exception_handler
    
    
def rest_exception_handler(exc, context):
    response = exception_handler(exc, context)
    
    def response_message(msg='Unspecified error. Try again later.'):
        return {'error': msg}
    
    def prepare_response(data):
        if isinstance(data, list) and len(data) > 0:
            result = response_message(msg=data[0])
        elif isinstance(data, str):
            result = response_message(msg=data)
        else:
            result = response_message()
    
        return result
    
    if response is not None:
        if 'error' in response.data:
            response.data = prepare_response(response.data.get('error'))
        elif 'detail' in response.data:
            response.data = prepare_response(response.data.get('detail'))
        else:
            response.data = {'fields': response.data, 'error': 'Some fields have errors.'}
    
    return response


def drf_404_handler(request, *args, **kwargs):
    return JsonResponse({'error': 'Not found.'}, status=status.HTTP_404_NOT_FOUND)

Django rest framework settings:

REST_FRAMEWORK = {
    ...
    'EXCEPTION_HANDLER': '<project_root_folder>.<error_handler.py>.rest_exception_handler',
    'NON_FIELD_ERRORS_KEY': 'error'
    ...
}

Base project urls

from .error_handler import drf_404_handler

...

handler404 = drf_404_handler

Example json responses (before / after):

   { "detail": "Not found" }

   { "error": "Not found" }

---

  {
    "email": ["This field is required."],
    "password": ["This field is required."]
  }

  {
    "fields": {
      "email": ["This field is required."],
      "password": ["This field is required."]
    },
    "error": "Some fields have errors."
  }

---

  {
    "non_field_errors": "Passwords don't match."
  }

  {
    "error": "Passwords don't match."
  }