views: Add a decorator to handle exceptions in JSON views

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/tests/test_views.py

@@ -3,10 +3,13 @@
 Tests for common FreedomBox views.
 """
 
+import json
+
 import pytest
+from django.http import JsonResponse
 from django.urls import resolve
 
-from plinth.views import get_breadcrumbs, is_safe_url
+from plinth.views import get_breadcrumbs, is_safe_url, json_exception
 
 
 def test_get_breadcrumbs(rf, test_menu):
@@ -82,3 +85,31 @@ def test_is_safe_url_valid_url(url):
 def test_is_safe_url_invalid_url(url):
     """Test invalid URLs for safe URL checks."""
     assert not is_safe_url(url)
+
+
+def test_json_exception(rf):
+    """Test handling exceptions in JSON views."""
+
+    @json_exception
+    def error_view(request):
+        raise Exception('exception-message')
+
+    assert error_view.__name__ == 'error_view'
+
+    request = rf.get('')
+    response = error_view(request)
+    assert response.status_code == 500
+    json_content = json.loads(response.content)
+    assert not json_content['result']
+    assert json_content['error_name'] == 'Exception'
+    assert json_content['error_string'] == 'exception-message'
+
+    def success_view(request):
+        return JsonResponse({'result': True, 'error_string': None})
+
+    request = rf.get('')
+    response = success_view(request)
+    assert response.status_code == 200
+    json_content = json.loads(response.content)
+    assert json_content['result']
+    assert json_content['error_string'] is None

plinth/views.py

@@ -3,10 +3,13 @@
 Main FreedomBox views.
 """
 
+import functools
+import logging
 import random
 import time
 import traceback
 import urllib.parse
+from collections.abc import Callable
 
 from django.contrib import messages
 from django.core.exceptions import ImproperlyConfigured
@@ -33,6 +36,8 @@ from plinth.translation import get_language_from_request, set_language
 
 from . import forms, frontpage, operation, setup
 
+logger = logging.getLogger(__name__)
+
 REDIRECT_FIELD_NAME = 'next'
 
 
@@ -683,6 +688,7 @@ class AppLogsView(TemplateView):
 def notification_dismiss(request, id):
     """Dismiss a notification."""
     from django.http import HttpResponse
+
     from .notification import Notification
     notes = Notification.list(key=id, user=request.user)
     if notes:
@@ -697,3 +703,24 @@ def notification_dismiss(request, id):
         return response
 
     return HttpResponseRedirect(_get_redirect_url_from_param(request))
+
+
+def json_exception(view_func: Callable):
+    """View decorator to return an view exception in JSON format."""
+
+    @functools.wraps(view_func)
+    def wrapper(*args, **kwargs):
+        """Wrapper over view function to handle exceptions."""
+        try:
+            return view_func(*args, **kwargs)
+        except Exception as exception:
+            logger.exception('Error running view %s - %s', view_func.__name__,
+                             exception)
+            return JsonResponse(
+                {
+                    'result': False,
+                    'error_name': type(exception).__name__,
+                    'error_string': str(exception)
+                }, status=500)  # Internal server error
+
+    return wrapper