Added generic 500 and 400 JSON error handlers. (#5904)

* Added generic 500 and 400 JSON error handlers.
* Docs for generic error views.

Author: carltongibson

Diff for: docs/api-guide/exceptions.md

@@ -230,5 +230,33 @@ The generic views use the `raise_exception=True` flag, which means that you can
 
 By default this exception results in a response with the HTTP status code "400 Bad Request".
 
+
+---
+
+# Generic Error Views
+
+Django REST Framework provides two error views suitable for providing generic JSON `500` Server Error and
+`400` Bad Request responses. (Django's default error views provide HTML responses, which may not be appropriate for an
+API-only application.)
+
+Use these as per [Django's Customizing error views documentation][django-custom-error-views].
+
+## `rest_framework.exceptions.server_error`
+
+Returns a response with status code `500` and `application/json` content type.
+
+Set as `handler500`:
+
+    handler500 = 'rest_framework.exceptions.server_error'
+
+## `rest_framework.exceptions.server_error`
+
+Returns a response with status code `400` and `application/json` content type.
+
+Set as `handler400`:
+
+    handler400 = 'rest_framework.exceptions.bad_request'
+
 [cite]: https://doughellmann.com/blog/2009/06/19/python-exception-handling-techniques/
 [authentication]: authentication.md
+[django-custom-error-views]: https://docs.djangoproject.com/en/dev/topics/http/views/#customizing-error-views

Diff for: rest_framework/exceptions.py

@@ -8,6 +8,7 @@
 
 import math
 
+from django.http import JsonResponse
 from django.utils import six
 from django.utils.encoding import force_text
 from django.utils.translation import ugettext_lazy as _
@@ -235,3 +236,23 @@ def __init__(self, wait=None, detail=None, code=None):
                                      wait))))
         self.wait = wait
         super(Throttled, self).__init__(detail, code)
+
+
+def server_error(request, *args, **kwargs):
+    """
+    Generic 500 error handler.
+    """
+    data = {
+        'error': 'Server Error (500)'
+    }
+    return JsonResponse(data, status=status.HTTP_500_INTERNAL_SERVER_ERROR)
+
+
+def bad_request(request, exception, *args, **kwargs):
+    """
+    Generic 400 error handler.
+    """
+    data = {
+        'error': 'Bad Request (400)'
+    }
+    return JsonResponse(data, status=status.HTTP_400_BAD_REQUEST)

Diff for: tests/test_exceptions.py

@@ -1,11 +1,13 @@
+# -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
-from django.test import TestCase
+from django.test import RequestFactory, TestCase
 from django.utils import six, translation
 from django.utils.translation import ugettext_lazy as _
 
 from rest_framework.exceptions import (
-    APIException, ErrorDetail, Throttled, _get_error_details
+    APIException, ErrorDetail, Throttled, _get_error_details, bad_request,
+    server_error
 )
 
 
@@ -87,3 +89,18 @@ def test_message(self):
         # this test largely acts as a sanity test to ensure the translation files are present.
         self.assertEqual(_('A server error occurred.'), 'Une erreur du serveur est survenue.')
         self.assertEqual(six.text_type(APIException()), 'Une erreur du serveur est survenue.')
+
+
+def test_server_error():
+    request = RequestFactory().get('/')
+    response = server_error(request)
+    assert response.status_code == 500
+    assert response["content-type"] == 'application/json'
+
+
+def test_bad_request():
+    request = RequestFactory().get('/')
+    exception = Exception('Something went wrong — Not used')
+    response = bad_request(request, exception)
+    assert response.status_code == 400
+    assert response["content-type"] == 'application/json'