Issue 431: return all exceptions as JSON:API error objects

.gitignore

@@ -31,11 +31,15 @@ pip-delete-this-directory.txt
 
 # PyTest cache
 .cache/
+.pytest_cache/
+
 
 # Tox
 .tox/
 .cache/
 .python-version
+.coverage
+htmlcov/
 
 # VirtualEnv
 .venv/

CHANGELOG.md

@@ -1,7 +1,12 @@
 v2.5.0 - [unreleased]
+
 * Add new pagination classes based on JSON:API query parameter *recommendations*:
   * JsonApiPageNumberPagination and JsonApiLimitOffsetPagination. See [usage docs](docs/usage.md#pagination).
   * Deprecates PageNumberPagination and LimitOffsetPagination.
+* Add exception handling improvements:
+  * Document JSON_API_UNIFORM_EXCEPTIONS setting.
+  * Catch all exceptions not caught by DRF and format as JSON API error objects instead of returning HTML error pages.
+  * handle missing fields exception
 
 v2.4.0 - Released January 25, 2018
 

docs/usage.md

@@ -82,6 +82,14 @@ class MyLimitPagination(JsonApiLimitOffsetPagination):
     max_limit = None
 ```
 
+### Exception handling
+
+For the `exception_handler` class, if the optional `JSON_API_UNIFORM_EXCEPTIONS` is set to True,
+all exceptions will respond with the JSON API [error format](http://jsonapi.org/format/#error-objects).
+
+When `JSON_API_UNIFORM_EXCEPTIONS` is False (the default), non-JSON API views will respond
+with the normal DRF error format.
+
 ### Performance Testing
 
 If you are trying to see if your viewsets are configured properly to optimize performance,

example/tests/test_views.py

@@ -1,15 +1,24 @@
 import json
+import sys
 
+import pytest
 from django.test import RequestFactory
 from django.utils import timezone
 from rest_framework.reverse import reverse
 from rest_framework.test import APITestCase, force_authenticate
 
 from rest_framework_json_api.utils import format_resource_type
+from rest_framework_json_api.views import ModelViewSet
 
 from . import TestBase
 from .. import views
 from example.models import Author, Blog, Comment, Entry
+from example.serializers import BlogSerializer
+
+try:
+    from unittest import mock
+except ImportError:
+    import mock
 
 
 class TestRelationshipView(APITestCase):
@@ -280,3 +289,32 @@ def test_no_content_response(self):
         response = self.client.delete(url)
         assert response.status_code == 204, response.rendered_content.decode()
         assert len(response.rendered_content) == 0, response.rendered_content.decode()
+
+
+class BadBlogViewSet(ModelViewSet):
+    queryset = Blog.objects.all()
+    serializer_class = BlogSerializer
+
+    def get_queryset(self, *args, **kwargs):
+        return self.queryset.filter(foo=1)
+
+
+@pytest.mark.xfail((sys.version_info.major, sys.version_info.minor) == (2, 7),
+                   reason="python2.7 mock raises "
+                   "'unbound method get_queryset() must be called with BadBlogViewSet "
+                   "instance as first argument (got nothing instead)' "
+                   "rather than working properly as does python3.x mock")
+class TestViewExceptions(TestBase):
+    def setUp(self):
+        self.blog = Blog.objects.create(name='Some Blog', tagline="It's a blog")
+
+    @mock.patch(
+        'example.views.BlogViewSet.get_queryset',
+        new=BadBlogViewSet.get_queryset)
+    def test_field_error_exception(self):
+        url = '/blogs'
+        response = self.client.get(url)
+        self.assertEqual(response.data[0]['code'], "field_error",
+                         msg=response.data[0]['detail'])
+        self.assertEqual(response.data[0]['source']['parameter'], "foo",
+                         msg=response.data[0]['detail'])

rest_framework_json_api/exceptions.py

@@ -1,5 +1,9 @@
+import re
+
+from django.core.exceptions import FieldDoesNotExist, FieldError
 from django.utils.translation import ugettext_lazy as _
 from rest_framework import exceptions, status
+from rest_framework.response import Response
 
 from rest_framework_json_api import utils
 
@@ -14,6 +18,52 @@ def rendered_with_json_api(view):
     return False
 
 
+def unhandled_drf_exception_handler(exc, context):
+    """
+    Deal with exceptions that DRF doesn't catch and return a JSON:API errors object.
+
+    For model query parameters, attempt to identify the parameter that caused the exception:
+    "Cannot resolve keyword 'xname' into field. Choices are: name, title, ...."
+    Unfortunately there's no "clean" way to identify which field caused the exception other than
+    parsing the error message. If the parse fails, a more generic error is reported.
+
+    Even a 500 error for a jsonapi view should return a jsonapi error object, not an HTML response.
+    """
+    if not rendered_with_json_api(context['view']):
+        return None
+    keymatch = re.compile(r"^Cannot resolve keyword '(?P<keyword>\w+)' into field.")
+    if isinstance(exc, (FieldError, FieldDoesNotExist,)):
+        matched = keymatch.match(str(exc))
+        bad_kw = matched.group("keyword") if matched else "?"
+        status_code = 400
+        errors = [
+            {
+                "status": status_code,
+                "code": "field_error",
+                "title": "Field error",
+                "detail": str(exc),
+                "source": {
+                    "pointer": context["request"].path,
+                    "parameter": bad_kw
+                }
+            }
+        ]
+    else:
+        status_code = 500
+        errors = [
+            {
+                "status": status_code,
+                "code": "server_error",
+                "title": "Internal Server Error",
+                "detail": str(exc),
+                "source": {
+                    "pointer": context["request"].path,
+                }
+            }
+        ]
+    return Response(errors, status=status_code)
+
+
 def exception_handler(exc, context):
     # Import this here to avoid potential edge-case circular imports, which
     # crashes with:
@@ -26,7 +76,7 @@ def exception_handler(exc, context):
     # Render exception with DRF
     response = drf_exception_handler(exc, context)
     if not response:
-        return response
+        return unhandled_drf_exception_handler(exc, context)
 
     # Use regular DRF format if not rendered by DRF JSON API and not uniform
     is_json_api_view = rendered_with_json_api(context['view'])

tox.ini

@@ -7,13 +7,16 @@ deps =
     django111: Django>=1.11,<1.12
     drf36: djangorestframework>=3.6.3,<3.7
     drf37: djangorestframework>=3.7.0,<3.8
+    coverage
 
 setenv =
     PYTHONPATH = {toxinidir}
     DJANGO_SETTINGS_MODULE=example.settings.test
 
 commands =
-    python setup.py test {posargs}
+    coverage erase
+    coverage run setup.py test {posargs}
+    coverage html --include=rest_framework_json_api/*
 
 [testenv:isort]
 deps =