Add custom exception handler for Django REST Framework

Add a custom exception handler to wrap all exceptions that are not handled
by the REST framework's default exception handler into a JSON response
with a 500 Internal Server Error HTTP status code.

Author: hoangpn

promgen/middleware.py

@@ -18,12 +18,15 @@
 """
 
 import logging
+from http import HTTPStatus
 from threading import local
 
 from django.contrib import messages
 from django.db.models import prefetch_related_objects
+from django.http import JsonResponse
+from rest_framework import views, exceptions
 
-from promgen import models
+from promgen import models, settings
 from promgen.signals import trigger_write_config, trigger_write_rules, trigger_write_urls
 
 logger = logging.getLogger(__name__)
@@ -67,3 +70,18 @@ def __call__(self, request):
 
 def get_current_user():
     return getattr(_user, "value", None)
+
+
+def custom_exception_handler(exc, context):
+    # Call REST framework's default exception handler first,
+    # to get the standard error response.
+    response = views.exception_handler(exc, context)
+
+    if response is None:
+        # If an exception is raised that we don't handle, we will return a 500 error
+        # with the exception message. This is useful for debugging in development
+        if settings.DEBUG:
+            return JsonResponse({"detail": str(exc)}, status=HTTPStatus.INTERNAL_SERVER_ERROR)
+        return exceptions.server_error(context["request"])
+
+    return response

promgen/settings.py

@@ -198,6 +198,7 @@
     ),
     "DEFAULT_FILTER_BACKENDS": ("django_filters.rest_framework.DjangoFilterBackend",),
     "DEFAULT_SCHEMA_CLASS": "promgen.schemas.CustomSchema",
+    "EXCEPTION_HANDLER": "promgen.middleware.custom_exception_handler",
 }
 
 # If CELERY_BROKER_URL is set in our environment, then we configure celery as