Merge pull request #61 from HackSoftware/exception-handling

Exception handling

Author: RadoRado

.env.example

@@ -0,0 +1 @@
+PYTHONBREAKPOINT=ipdb.set_trace

config/settings/base.py

@@ -12,11 +12,12 @@
 
 import os
 
-from .env_reader import env
+from .env_reader import env, environ
 
 # Build paths inside the project like this: os.path.join(BASE_DIR, ...)
-BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+BASE_DIR = environ.Path(__file__) - 3
 
+env.read_env(os.path.join(BASE_DIR, ".env"))
 
 # Quick-start development settings - unsuitable for production
 # See https://docs.djangoproject.com/en/3.0/howto/deployment/checklist/
@@ -33,10 +34,12 @@
 # Application definition
 
 LOCAL_APPS = [
+    'styleguide_example.core.apps.CoreConfig',
     'styleguide_example.common.apps.CommonConfig',
     'styleguide_example.tasks.apps.TasksConfig',
     'styleguide_example.api.apps.ApiConfig',
     'styleguide_example.users.apps.UsersConfig',
+    'styleguide_example.errors.apps.ErrorsConfig',
 ]
 
 THIRD_PARTY_APPS = [
@@ -155,7 +158,8 @@
 STATICFILES_STORAGE = 'whitenoise.storage.CompressedManifestStaticFilesStorage'
 
 REST_FRAMEWORK = {
-    'EXCEPTION_HANDLER': 'styleguide_example.api.errors.custom_exception_handler',
+    'EXCEPTION_HANDLER': 'styleguide_example.api.exception_handlers.drf_default_with_modifications_exception_handler',
+    # 'EXCEPTION_HANDLER': 'styleguide_example.api.exception_handlers.hacksoft_proposed_exception_handler',
     'DEFAULT_FILTER_BACKENDS': (
         'django_filters.rest_framework.DjangoFilterBackend',
     ),

styleguide_example/api/errors.py

@@ -0,0 +1,81 @@
+from django.core.exceptions import ValidationError as DjangoValidationError, PermissionDenied
+from django.http import Http404
+
+from rest_framework.views import exception_handler
+from rest_framework import exceptions
+from rest_framework.serializers import as_serializer_error
+from rest_framework.response import Response
+
+from styleguide_example.core.exceptions import ApplicationError
+
+
+def drf_default_with_modifications_exception_handler(exc, ctx):
+    if isinstance(exc, DjangoValidationError):
+        exc = exceptions.ValidationError(as_serializer_error(exc))
+
+    if isinstance(exc, Http404):
+        exc = exceptions.NotFound()
+
+    if isinstance(exc, PermissionDenied):
+        exc = exceptions.PermissionDenied()
+
+    response = exception_handler(exc, ctx)
+
+    # If unexpected error occurs (server error, etc.)
+    if response is None:
+        return response
+
+    if isinstance(exc.detail, (list, dict)):
+        response.data = {
+            "detail": response.data
+        }
+
+    return response
+
+
+def hacksoft_proposed_exception_handler(exc, ctx):
+    """
+    {
+        "message": "Error message",
+        "extra": {}
+    }
+    """
+    if isinstance(exc, DjangoValidationError):
+        exc = exceptions.ValidationError(as_serializer_error(exc))
+
+    if isinstance(exc, Http404):
+        exc = exceptions.NotFound()
+
+    if isinstance(exc, PermissionDenied):
+        exc = exceptions.PermissionDenied()
+
+    response = exception_handler(exc, ctx)
+
+    # If unexpected error occurs (server error, etc.)
+    if response is None:
+        if isinstance(exc, ApplicationError):
+            data = {
+                "message": exc.message,
+                "extra": exc.extra
+            }
+            return Response(data, status=400)
+
+        return response
+
+    if isinstance(exc.detail, (list, dict)):
+        response.data = {
+            "detail": response.data
+        }
+
+    if isinstance(exc, exceptions.ValidationError):
+        response.data["message"] = "Validation error"
+        response.data["extra"] = {
+            "fields": response.data["detail"]
+        }
+    else:
+        response.data["message"] = response.data["detail"]
+        response.data["extra"] = {}
+
+    del response.data["detail"]
+
+    return response

styleguide_example/api/exception_handlers.py

@@ -1,16 +1,12 @@
 from importlib import import_module
 
-from django.core.exceptions import ValidationError
 from django.conf import settings
 
 from django.contrib import auth
 
-from rest_framework import exceptions as rest_exceptions
 from rest_framework.permissions import IsAuthenticated
 from rest_framework.authentication import SessionAuthentication, BaseAuthentication
 
-from styleguide_example.api.errors import get_error_message
-
 
 def get_auth_header(headers):
     value = headers.get('Authorization')
@@ -65,24 +61,3 @@ def enforce_csrf(self, request):
 class ApiAuthMixin:
     authentication_classes = (CsrfExemptedSessionAuthentication, SessionAsHeaderAuthentication)
     permission_classes = (IsAuthenticated, )
-
-
-class ApiErrorsMixin:
-    """
-    Mixin that transforms Django and Python exceptions into rest_framework ones.
-    without the mixin, they return 500 status code which is not desired.
-    """
-    expected_exceptions = {
-        ValueError: rest_exceptions.ValidationError,
-        ValidationError: rest_exceptions.ValidationError,
-        PermissionError: rest_exceptions.PermissionDenied
-    }
-
-    def handle_exception(self, exc):
-        if isinstance(exc, tuple(self.expected_exceptions.keys())):
-            drf_exception_class = self.expected_exceptions[exc.__class__]
-            drf_exception = drf_exception_class(get_error_message(exc))
-
-            return super().handle_exception(drf_exception)
-
-        return super().handle_exception(exc)