Error codes (#4550)

Add error codes to `APIException`

docs/api-guide/exceptions.md

@@ -98,7 +98,7 @@ Note that the exception handler will only be called for responses generated by r
 
 The **base class** for all exceptions raised inside an `APIView` class or `@api_view`.
 
-To provide a custom exception, subclass `APIException` and set the `.status_code` and `.default_detail` properties on the class.
+To provide a custom exception, subclass `APIException` and set the `.status_code`, `.default_detail`, and `default_code` attributes on the class.
 
 For example, if your API relies on a third party service that may sometimes be unreachable, you might want to implement an exception for the "503 Service Unavailable" HTTP response code.  You could do this like so:
 
@@ -107,10 +107,42 @@ For example, if your API relies on a third party service that may sometimes be u
     class ServiceUnavailable(APIException):
         status_code = 503
         default_detail = 'Service temporarily unavailable, try again later.'
+        default_code = 'service_unavailable'
+
+#### Inspecting API exceptions
+
+There are a number of different properties available for inspecting the status
+of an API exception. You can use these to build custom exception handling
+for your project.
+
+The available attributes and methods are:
+
+* `.detail` - Return the textual description of the error.
+* `.get_codes()` - Return the code identifier of the error.
+* `.full_details()` - Return both the textual description and the code identifier.
+
+In most cases the error detail will be a simple item:
+
+    >>> print(exc.detail)
+    You do not have permission to perform this action.
+    >>> print(exc.get_codes())
+    permission_denied
+    >>> print(exc.full_details())
+    {'message':'You do not have permission to perform this action.','code':'permission_denied'}
+
+In the case of validation errors the error detail will be either a list or
+dictionary of items:
+
+    >>> print(exc.detail)
+    {"name":"This field is required.","age":"A valid integer is required."}
+    >>> print(exc.get_codes())
+    {"name":"required","age":"invalid"}
+    >>> print(exc.get_full_details())
+    {"name":{"message":"This field is required.","code":"required"},"age":{"message":"A valid integer is required.","code":"invalid"}}
 
 ## ParseError
 
-**Signature:** `ParseError(detail=None)`
+**Signature:** `ParseError(detail=None, code=None)`
 
 Raised if the request contains malformed data when accessing `request.data`.
 
@@ -118,7 +150,7 @@ By default this exception results in a response with the HTTP status code "400 B
 
 ## AuthenticationFailed
 
-**Signature:** `AuthenticationFailed(detail=None)`
+**Signature:** `AuthenticationFailed(detail=None, code=None)`
 
 Raised when an incoming request includes incorrect authentication.
 
@@ -126,7 +158,7 @@ By default this exception results in a response with the HTTP status code "401 U
 
 ## NotAuthenticated
 
-**Signature:** `NotAuthenticated(detail=None)`
+**Signature:** `NotAuthenticated(detail=None, code=None)`
 
 Raised when an unauthenticated request fails the permission checks.
 
@@ -134,7 +166,7 @@ By default this exception results in a response with the HTTP status code "401 U
 
 ## PermissionDenied
 
-**Signature:** `PermissionDenied(detail=None)`
+**Signature:** `PermissionDenied(detail=None, code=None)`
 
 Raised when an authenticated request fails the permission checks.
 
@@ -142,7 +174,7 @@ By default this exception results in a response with the HTTP status code "403 F
 
 ## NotFound
 
-**Signature:** `NotFound(detail=None)`
+**Signature:** `NotFound(detail=None, code=None)`
 
 Raised when a resource does not exists at the given URL. This exception is equivalent to the standard `Http404` Django exception.
 
@@ -150,7 +182,7 @@ By default this exception results in a response with the HTTP status code "404 N
 
 ## MethodNotAllowed
 
-**Signature:** `MethodNotAllowed(method, detail=None)`
+**Signature:** `MethodNotAllowed(method, detail=None, code=None)`
 
 Raised when an incoming request occurs that does not map to a handler method on the view.
 
@@ -158,7 +190,7 @@ By default this exception results in a response with the HTTP status code "405 M
 
 ## NotAcceptable
 
-**Signature:** `NotAcceptable(detail=None)`
+**Signature:** `NotAcceptable(detail=None, code=None)`
 
 Raised when an incoming request occurs with an `Accept` header that cannot be satisfied by any of the available renderers.
 
@@ -166,7 +198,7 @@ By default this exception results in a response with the HTTP status code "406 N
 
 ## UnsupportedMediaType
 
-**Signature:** `UnsupportedMediaType(media_type, detail=None)`
+**Signature:** `UnsupportedMediaType(media_type, detail=None, code=None)`
 
 Raised if there are no parsers that can handle the content type of the request data when accessing `request.data`.
 
@@ -174,7 +206,7 @@ By default this exception results in a response with the HTTP status code "415 U
 
 ## Throttled
 
-**Signature:** `Throttled(wait=None, detail=None)`
+**Signature:** `Throttled(wait=None, detail=None, code=None)`
 
 Raised when an incoming request fails the throttling checks.
 
@@ -182,7 +214,7 @@ By default this exception results in a response with the HTTP status code "429 T
 
 ## ValidationError
 
-**Signature:** `ValidationError(detail)`
+**Signature:** `ValidationError(detail, code=None)`
 
 The `ValidationError` exception is slightly different from the other `APIException` classes:
 

rest_framework/authtoken/serializers.py

@@ -21,13 +21,13 @@ class AuthTokenSerializer(serializers.Serializer):
                 # (Assuming the default `ModelBackend` authentication backend.)
                 if not user.is_active:
                     msg = _('User account is disabled.')
-                    raise serializers.ValidationError(msg)
+                    raise serializers.ValidationError(msg, code='authorization')
             else:
                 msg = _('Unable to log in with provided credentials.')
-                raise serializers.ValidationError(msg)
+                raise serializers.ValidationError(msg, code='authorization')
         else:
             msg = _('Must include "username" and "password".')
-            raise serializers.ValidationError(msg)
+            raise serializers.ValidationError(msg, code='authorization')
 
         attrs['user'] = user
         return attrs

rest_framework/exceptions.py

@@ -17,27 +17,61 @@ from rest_framework import status
 from rest_framework.utils.serializer_helpers import ReturnDict, ReturnList
 
 
-def _force_text_recursive(data):
+def _get_error_details(data, default_code=None):
     """
     Descend into a nested data structure, forcing any
-    lazy translation strings into plain text.
+    lazy translation strings or strings into `ErrorDetail`.
     """
     if isinstance(data, list):
         ret = [
-            _force_text_recursive(item) for item in data
+            _get_error_details(item, default_code) for item in data
         ]
         if isinstance(data, ReturnList):
             return ReturnList(ret, serializer=data.serializer)
         return ret
     elif isinstance(data, dict):
         ret = {
-            key: _force_text_recursive(value)
+            key: _get_error_details(value, default_code)
             for key, value in data.items()
         }
         if isinstance(data, ReturnDict):
             return ReturnDict(ret, serializer=data.serializer)
         return ret
-    return force_text(data)
+
+    text = force_text(data)
+    code = getattr(data, 'code', default_code)
+    return ErrorDetail(text, code)
+
+
+def _get_codes(detail):
+    if isinstance(detail, list):
+        return [_get_codes(item) for item in detail]
+    elif isinstance(detail, dict):
+        return {key: _get_codes(value) for key, value in detail.items()}
+    return detail.code
+
+
+def _get_full_details(detail):
+    if isinstance(detail, list):
+        return [_get_full_details(item) for item in detail]
+    elif isinstance(detail, dict):
+        return {key: _get_full_details(value) for key, value in detail.items()}
+    return {
+        'message': detail,
+        'code': detail.code
+    }
+
+
+class ErrorDetail(six.text_type):
+    """
+    A string-like object that can additionally
+    """
+    code = None
+
+    def __new__(cls, string, code=None):
+        self = super(ErrorDetail, cls).__new__(cls, string)
+        self.code = code
+        return self
 
 
 class APIException(Exception):
@@ -47,16 +81,35 @@ class APIException(Exception):
     """
     status_code = status.HTTP_500_INTERNAL_SERVER_ERROR
     default_detail = _('A server error occurred.')
+    default_code = 'error'
 
-    def __init__(self, detail=None):
-        if detail is not None:
-            self.detail = force_text(detail)
-        else:
-            self.detail = force_text(self.default_detail)
+    def __init__(self, detail=None, code=None):
+        if detail is None:
+            detail = self.default_detail
+        if code is None:
+            code = self.default_code
+
+        self.detail = _get_error_details(detail, code)
 
     def __str__(self):
         return self.detail
 
+    def get_codes(self):
+        """
+        Return only the code part of the error details.
+
+        Eg. {"name": ["required"]}
+        """
+        return _get_codes(self.detail)
+
+    def get_full_details(self):
+        """
+        Return both the message & code parts of the error details.
+
+        Eg. {"name": [{"message": "This field is required.", "code": "required"}]}
+        """
+        return _get_full_details(self.detail)
+
 
 # The recommended style for using `ValidationError` is to keep it namespaced
 # under `serializers`, in order to minimize potential confusion with Django's
@@ -67,13 +120,21 @@ class APIException(Exception):
 
 class ValidationError(APIException):
     status_code = status.HTTP_400_BAD_REQUEST
+    default_detail = _('Invalid input.')
+    default_code = 'invalid'
 
-    def __init__(self, detail):
-        # For validation errors the 'detail' key is always required.
-        # The details should always be coerced to a list if not already.
+    def __init__(self, detail, code=None):
+        if detail is None:
+            detail = self.default_detail
+        if code is None:
+            code = self.default_code
+
+        # For validation failures, we may collect may errors together, so the
+        # details should always be coerced to a list if not already.
         if not isinstance(detail, dict) and not isinstance(detail, list):
             detail = [detail]
-        self.detail = _force_text_recursive(detail)
+
+        self.detail = _get_error_details(detail, code)
 
     def __str__(self):
         return six.text_type(self.detail)
@@ -82,62 +143,63 @@ class ValidationError(APIException):
 class ParseError(APIException):
     status_code = status.HTTP_400_BAD_REQUEST
     default_detail = _('Malformed request.')
+    default_code = 'parse_error'
 
 
 class AuthenticationFailed(APIException):
     status_code = status.HTTP_401_UNAUTHORIZED
     default_detail = _('Incorrect authentication credentials.')
+    default_code = 'authentication_failed'
 
 
 class NotAuthenticated(APIException):
     status_code = status.HTTP_401_UNAUTHORIZED
     default_detail = _('Authentication credentials were not provided.')
+    default_code = 'not_authenticated'
 
 
 class PermissionDenied(APIException):
     status_code = status.HTTP_403_FORBIDDEN
     default_detail = _('You do not have permission to perform this action.')
+    default_code = 'permission_denied'
 
 
 class NotFound(APIException):
     status_code = status.HTTP_404_NOT_FOUND
     default_detail = _('Not found.')
+    default_code = 'not_found'
 
 
 class MethodNotAllowed(APIException):
     status_code = status.HTTP_405_METHOD_NOT_ALLOWED
     default_detail = _('Method "{method}" not allowed.')
+    default_code = 'method_not_allowed'
 
-    def __init__(self, method, detail=None):
-        if detail is not None:
-            self.detail = force_text(detail)
-        else:
-            self.detail = force_text(self.default_detail).format(method=method)
+    def __init__(self, method, detail=None, code=None):
+        if detail is None:
+            detail = force_text(self.default_detail).format(method=method)
+        super(MethodNotAllowed, self).__init__(detail, code)
 
 
 class NotAcceptable(APIException):
     status_code = status.HTTP_406_NOT_ACCEPTABLE
     default_detail = _('Could not satisfy the request Accept header.')
+    default_code = 'not_acceptable'
 
-    def __init__(self, detail=None, available_renderers=None):
-        if detail is not None:
-            self.detail = force_text(detail)
-        else:
-            self.detail = force_text(self.default_detail)
+    def __init__(self, detail=None, code=None, available_renderers=None):
         self.available_renderers = available_renderers
+        super(NotAcceptable, self).__init__(detail, code)
 
 
 class UnsupportedMediaType(APIException):
     status_code = status.HTTP_415_UNSUPPORTED_MEDIA_TYPE
     default_detail = _('Unsupported media type "{media_type}" in request.')
+    default_code = 'unsupported_media_type'
 
-    def __init__(self, media_type, detail=None):
-        if detail is not None:
-            self.detail = force_text(detail)
-        else:
-            self.detail = force_text(self.default_detail).format(
-                media_type=media_type
-            )
+    def __init__(self, media_type, detail=None, code=None):
+        if detail is None:
+            detail = force_text(self.default_detail).format(media_type=media_type)
+        super(UnsupportedMediaType, self).__init__(detail, code)
 
 
 class Throttled(APIException):
@@ -145,12 +207,10 @@ class Throttled(APIException):
     default_detail = _('Request was throttled.')
     extra_detail_singular = 'Expected available in {wait} second.'
     extra_detail_plural = 'Expected available in {wait} seconds.'
+    default_code = 'throttled'
 
-    def __init__(self, wait=None, detail=None):
-        if detail is not None:
-            self.detail = force_text(detail)
-        else:
-            self.detail = force_text(self.default_detail)
+    def __init__(self, wait=None, detail=None, code=None):
+        super(Throttled, self).__init__(detail, code)
 
         if wait is None:
             self.wait = None

rest_framework/fields.py

@@ -34,7 +34,7 @@ from rest_framework import ISO_8601
 from rest_framework.compat import (
     get_remote_field, unicode_repr, unicode_to_repr, value_from_object
 )
-from rest_framework.exceptions import ValidationError
+from rest_framework.exceptions import ErrorDetail, ValidationError
 from rest_framework.settings import api_settings
 from rest_framework.utils import html, humanize_datetime, representation
 
@@ -224,6 +224,18 @@ def iter_options(grouped_choices, cutoff=None, cutoff_text=None):
         yield Option(value='n/a', display_text=cutoff_text, disabled=True)
 
 
+def get_error_detail(exc_info):
+    """
+    Given a Django ValidationError, return a list of ErrorDetail,
+    with the `code` populated.
+    """
+    code = getattr(exc_info, 'code', None) or 'invalid'
+    return [
+        ErrorDetail(msg, code=code)
+        for msg in exc_info.messages
+    ]
+
+
 class CreateOnlyDefault(object):
     """
     This class may be used to provide default values that are only used
@@ -525,7 +537,7 @@ class Field(object):
                     raise
                 errors.extend(exc.detail)
             except DjangoValidationError as exc:
-                errors.extend(exc.messages)
+                errors.extend(get_error_detail(exc))
         if errors:
             raise ValidationError(errors)
 
@@ -563,7 +575,7 @@ class Field(object):
             msg = MISSING_ERROR_MESSAGE.format(class_name=class_name, key=key)
             raise AssertionError(msg)
         message_string = msg.format(**kwargs)
-        raise ValidationError(message_string)
+        raise ValidationError(message_string, code=key)
 
     @cached_property
     def root(self):

rest_framework/serializers.py

@@ -291,32 +291,29 @@ class SerializerMetaclass(type):
         return super(SerializerMetaclass, cls).__new__(cls, name, bases, attrs)
 
 
-def get_validation_error_detail(exc):
+def as_serializer_error(exc):
     assert isinstance(exc, (ValidationError, DjangoValidationError))
 
     if isinstance(exc, DjangoValidationError):
-        # Normally you should raise `serializers.ValidationError`
-        # inside your codebase, but we handle Django's validation
-        # exception class as well for simpler compat.
-        # Eg. Calling Model.clean() explicitly inside Serializer.validate()
-        return {
-            api_settings.NON_FIELD_ERRORS_KEY: list(exc.messages)
-        }
-    elif isinstance(exc.detail, dict):
+        detail = get_error_detail(exc)
+    else:
+        detail = exc.detail
+
+    if isinstance(detail, dict):
         # If errors may be a dict we use the standard {key: list of values}.
         # Here we ensure that all the values are *lists* of errors.
         return {
             key: value if isinstance(value, (list, dict)) else [value]
-            for key, value in exc.detail.items()
+            for key, value in detail.items()
         }
-    elif isinstance(exc.detail, list):
+    elif isinstance(detail, list):
         # Errors raised as a list are non-field errors.
         return {
-            api_settings.NON_FIELD_ERRORS_KEY: exc.detail
+            api_settings.NON_FIELD_ERRORS_KEY: detail
         }
     # Errors raised as a string are non-field errors.
     return {
-        api_settings.NON_FIELD_ERRORS_KEY: [exc.detail]
+        api_settings.NON_FIELD_ERRORS_KEY: [detail]
     }
 
 
@@ -410,7 +407,7 @@ class Serializer(BaseSerializer):
             value = self.validate(value)
             assert value is not None, '.validate() should return the validated data'
         except (ValidationError, DjangoValidationError) as exc:
-            raise ValidationError(detail=get_validation_error_detail(exc))
+            raise ValidationError(detail=as_serializer_error(exc))
 
         return value
 
@@ -424,7 +421,7 @@ class Serializer(BaseSerializer):
             )
             raise ValidationError({
                 api_settings.NON_FIELD_ERRORS_KEY: [message]
-            })
+            }, code='invalid')
 
         ret = OrderedDict()
         errors = OrderedDict()
@@ -440,7 +437,7 @@ class Serializer(BaseSerializer):
             except ValidationError as exc:
                 errors[field.field_name] = exc.detail
             except DjangoValidationError as exc:
-                errors[field.field_name] = list(exc.messages)
+                errors[field.field_name] = get_error_detail(exc)
             except SkipField:
                 pass
             else:
@@ -564,7 +561,7 @@ class ListSerializer(BaseSerializer):
             value = self.validate(value)
             assert value is not None, '.validate() should return the validated data'
         except (ValidationError, DjangoValidationError) as exc:
-            raise ValidationError(detail=get_validation_error_detail(exc))
+            raise ValidationError(detail=as_serializer_error(exc))
 
         return value
 
@@ -581,13 +578,13 @@ class ListSerializer(BaseSerializer):
             )
             raise ValidationError({
                 api_settings.NON_FIELD_ERRORS_KEY: [message]
-            })
+            }, code='not_a_list')
 
         if not self.allow_empty and len(data) == 0:
             message = self.error_messages['empty']
             raise ValidationError({
                 api_settings.NON_FIELD_ERRORS_KEY: [message]
-            })
+            }, code='empty')
 
         ret = []
         errors = []

rest_framework/validators.py

@@ -80,7 +80,7 @@ class UniqueValidator(object):
         queryset = self.filter_queryset(value, queryset)
         queryset = self.exclude_current_instance(queryset)
         if qs_exists(queryset):
-            raise ValidationError(self.message)
+            raise ValidationError(self.message, code='unique')
 
     def __repr__(self):
         return unicode_to_repr('<%s(queryset=%s)>' % (
@@ -120,13 +120,13 @@ class UniqueTogetherValidator(object):
         if self.instance is not None:
             return
 
-        missing = {
+        missing_items = {
             field_name: self.missing_message
             for field_name in self.fields
             if field_name not in attrs
         }
-        if missing:
-            raise ValidationError(missing)
+        if missing_items:
+            raise ValidationError(missing_items, code='required')
 
     def filter_queryset(self, attrs, queryset):
         """
@@ -167,7 +167,8 @@ class UniqueTogetherValidator(object):
         ]
         if None not in checked_values and qs_exists(queryset):
             field_names = ', '.join(self.fields)
-            raise ValidationError(self.message.format(field_names=field_names))
+            message = self.message.format(field_names=field_names)
+            raise ValidationError(message, code='unique')
 
     def __repr__(self):
         return unicode_to_repr('<%s(queryset=%s, fields=%s)>' % (
@@ -204,13 +205,13 @@ class BaseUniqueForValidator(object):
         The `UniqueFor<Range>Validator` classes always force an implied
         'required' state on the fields they are applied to.
         """
-        missing = {
+        missing_items = {
             field_name: self.missing_message
             for field_name in [self.field, self.date_field]
             if field_name not in attrs
         }
-        if missing:
-            raise ValidationError(missing)
+        if missing_items:
+            raise ValidationError(missing_items, code='required')
 
     def filter_queryset(self, attrs, queryset):
         raise NotImplementedError('`filter_queryset` must be implemented.')
@@ -231,7 +232,9 @@ class BaseUniqueForValidator(object):
         queryset = self.exclude_current_instance(attrs, queryset)
         if qs_exists(queryset):
             message = self.message.format(date_field=self.date_field)
-            raise ValidationError({self.field: message})
+            raise ValidationError({
+                self.field: message
+            }, code='unique')
 
     def __repr__(self):
         return unicode_to_repr('<%s(queryset=%s, field=%s, date_field=%s)>' % (

tests/test_exceptions.py

@@ -3,19 +3,39 @@ from __future__ import unicode_literals
 from django.test import TestCase
 from django.utils.translation import ugettext_lazy as _
 
-from rest_framework.exceptions import _force_text_recursive
+from rest_framework.exceptions import ErrorDetail, _get_error_details
 
 
 class ExceptionTestCase(TestCase):
 
-    def test_force_text_recursive(self):
+    def test_get_error_details(self):
 
-        s = "sfdsfggiuytraetfdlklj"
-        self.assertEqual(_force_text_recursive(_(s)), s)
-        self.assertEqual(type(_force_text_recursive(_(s))), type(s))
+        example = "string"
+        lazy_example = _(example)
 
-        self.assertEqual(_force_text_recursive({'a': _(s)})['a'], s)
-        self.assertEqual(type(_force_text_recursive({'a': _(s)})['a']), type(s))
+        self.assertEqual(
+            _get_error_details(lazy_example),
+            example
+        )
+        assert isinstance(
+            _get_error_details(lazy_example),
+            ErrorDetail
+        )
 
-        self.assertEqual(_force_text_recursive([[_(s)]])[0][0], s)
-        self.assertEqual(type(_force_text_recursive([[_(s)]])[0][0]), type(s))
+        self.assertEqual(
+            _get_error_details({'nested': lazy_example})['nested'],
+            example
+        )
+        assert isinstance(
+            _get_error_details({'nested': lazy_example})['nested'],
+            ErrorDetail
+        )
+
+        self.assertEqual(
+            _get_error_details([[lazy_example]])[0][0],
+            example
+        )
+        assert isinstance(
+            _get_error_details([[lazy_example]])[0][0],
+            ErrorDetail
+        )

tests/test_validation.py

@@ -60,7 +60,7 @@ class TestNestedValidationError(TestCase):
             }
         })
 
-        self.assertEqual(serializers.get_validation_error_detail(e), {
+        self.assertEqual(serializers.as_serializer_error(e), {
             'nested': {
                 'field': ['error'],
             }

tests/test_validation_error.py

@@ -0,0 +1,101 @@
+from django.test import TestCase
+
+from rest_framework import serializers, status
+from rest_framework.decorators import api_view
+from rest_framework.response import Response
+from rest_framework.settings import api_settings
+from rest_framework.test import APIRequestFactory
+from rest_framework.views import APIView
+
+factory = APIRequestFactory()
+
+
+class ExampleSerializer(serializers.Serializer):
+    char = serializers.CharField()
+    integer = serializers.IntegerField()
+
+
+class ErrorView(APIView):
+    def get(self, request, *args, **kwargs):
+        ExampleSerializer(data={}).is_valid(raise_exception=True)
+
+
+@api_view(['GET'])
+def error_view(request):
+    ExampleSerializer(data={}).is_valid(raise_exception=True)
+
+
+class TestValidationErrorWithFullDetails(TestCase):
+    def setUp(self):
+        self.DEFAULT_HANDLER = api_settings.EXCEPTION_HANDLER
+
+        def exception_handler(exc, request):
+            data = exc.get_full_details()
+            return Response(data, status=status.HTTP_400_BAD_REQUEST)
+
+        api_settings.EXCEPTION_HANDLER = exception_handler
+
+        self.expected_response_data = {
+            'char': [{
+                'message': 'This field is required.',
+                'code': 'required',
+            }],
+            'integer': [{
+                'message': 'This field is required.',
+                'code': 'required'
+            }],
+        }
+
+    def tearDown(self):
+        api_settings.EXCEPTION_HANDLER = self.DEFAULT_HANDLER
+
+    def test_class_based_view_exception_handler(self):
+        view = ErrorView.as_view()
+
+        request = factory.get('/', content_type='application/json')
+        response = view(request)
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertEqual(response.data, self.expected_response_data)
+
+    def test_function_based_view_exception_handler(self):
+        view = error_view
+
+        request = factory.get('/', content_type='application/json')
+        response = view(request)
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertEqual(response.data, self.expected_response_data)
+
+
+class TestValidationErrorWithCodes(TestCase):
+    def setUp(self):
+        self.DEFAULT_HANDLER = api_settings.EXCEPTION_HANDLER
+
+        def exception_handler(exc, request):
+            data = exc.get_codes()
+            return Response(data, status=status.HTTP_400_BAD_REQUEST)
+
+        api_settings.EXCEPTION_HANDLER = exception_handler
+
+        self.expected_response_data = {
+            'char': ['required'],
+            'integer': ['required'],
+        }
+
+    def tearDown(self):
+        api_settings.EXCEPTION_HANDLER = self.DEFAULT_HANDLER
+
+    def test_class_based_view_exception_handler(self):
+        view = ErrorView.as_view()
+
+        request = factory.get('/', content_type='application/json')
+        response = view(request)
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertEqual(response.data, self.expected_response_data)
+
+    def test_function_based_view_exception_handler(self):
+        view = error_view
+
+        request = factory.get('/', content_type='application/json')
+        response = view(request)
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertEqual(response.data, self.expected_response_data)