API: Format HTTP 500 errors as JSON

tabbycat/api/exceptions.py

@@ -0,0 +1,24 @@
+import logging
+
+from django.conf import settings
+from rest_framework import status
+from rest_framework.response import Response
+from rest_framework.views import exception_handler as drf_exception_handler
+
+logger = logging.getLogger(__name__)
+
+
+def api_exception_handler(exc, context):
+    """Return JSON for unhandled errors instead of letting Django serve the HTML 500 page."""
+    response = drf_exception_handler(exc, context)
+    if response is not None:
+        return response
+
+    if settings.DEBUG:
+        return
+
+    logger.exception("Unhandled exception in API request")
+
+    data = {'detail': 'A server error occurred.'}
+
+    return Response(data, status=status.HTTP_500_INTERNAL_SERVER_ERROR)

tabbycat/api/tests/test_views.py

@@ -1,4 +1,5 @@
 import json
+from unittest.mock import patch
 
 from django.conf import settings
 from django.test import Client
@@ -33,6 +34,17 @@ def test_get_v1_root(self):
         })
 
 
+class APIExceptionHandlerTests(CompletedTournamentTestMixin, APITestCase):
+
+    @patch('api.views.TournamentViewSet.list', side_effect=RuntimeError('deliberate failure'))
+    def test_unhandled_exception_returns_json(self, _mock):
+        response = self.client.get(reverse('api-tournament-list'))
+        self.assertEqual(response.status_code, 500)
+        self.assertIn('application/json', response['Content-Type'])
+        payload = json.loads(response.content)
+        self.assertIn('detail', payload)
+
+
 class TournamentViewsetTests(CompletedTournamentTestMixin, APITestCase):
 
     def test_get_tournament_list(self):

tabbycat/settings/core.py

@@ -366,6 +366,7 @@
 # ==============================================================================
 
 REST_FRAMEWORK = {
+    'EXCEPTION_HANDLER': 'api.exceptions.api_exception_handler',
     'DEFAULT_RENDERER_CLASSES': [
         'rest_framework.renderers.JSONRenderer',
     ],