Django allow custom error handlers, like handler403 for handling of "Permission Denied" errors. This error can be raised with:
from django.core.exceptions import PermissionDenied
...
raise PermissionDenied('info')
The handler can then be:
def error_403_permission_denied(request):
...
How can the handler get access to the information given when raising the PermissionDenied exception, for example the 'info' string above, in order to show this as part of the HTML generated for the error?
I don't think this is possible currently. There was a ticket that was fixed in Django 1.9 that addresses this limitation - so from Django 1.9 you will be able to accept an exception argument in your view.
Related
I have a similar issue as this question about validating data in the Django REST Framework outside of a serializer:
Raise Validation Error In Pre_Save Using Django Rest Framework
My code:
def pre_save(self, obj):
data = self.request.DATA['users']
for user in data:
if not user in allowed_users:
raise ParseError('An unpermitted user has been included')
From the trace it looks like it's trying to send the response but it fails with:
"" needs to have a value for field before this many-to-many relationship can be used.
UPDATE:
I moved raising the ParseError into a get_serializer_class() method like so:
def get_serializer_class(self):
if 'users' in self.request.DATA:
# make sure the users are allowed
data = self.request.DATA['users']
for user in data:
if not user in allowed_users:
raise ParseError(detail='Unpermitted user')
return serializer
And this raises the exception, however, it does not return it using the REST framework's JSON response. Rather I get the django stack trace and a 500 error, which is not good.
Thanks!
Have a look at APIView's handle_exception — this is where DRF processes exceptions raised during the request.
From the docs:
The default implementation handles any subclass of rest_framework.exceptions.APIException, as well as Django's Http404 and PermissionDenied exceptions, and returns an appropriate error response.
If you need to customize the error responses your API returns you should subclass this method.
So you need to override this to handle ParseError exceptions too.
Also check out the DRF docs on Exceptions.
I hope that helps.
When the exception is raised in the pre_save method(), post_save(), or even in a post() method for the viewclass, it was being handled correctly by Django-REST-Framework. Had I been using curl or similar, the error would have been returned correctly.
This actually is a bug in the browsable API, which is what I was using to test - sending the data using the "Raw data" form. When trying to render the html response, DRF apparently tries to capture the "context" of the post. In this case, it wanted the saved/completed post.
That did not exist, so a Django rendering error was being thrown and that confused me.
When testing using curl, the response was accurate.
Note that putting it in the get_serializer_class() like I did caused it to go outside of the DRF exception handler so Django rendered it correctly and showed the error was being thrown correctly.
I am having difficulty raising a validation error using the Django Rest Framework.
I have an owner field. The owner field needs to access the request object. The documentation suggests using the following approach:
def pre_save(self, obj):
obj.owner = self.request.user
My problem is how to raise a validation error if this code fails. I tried raising an error inside the pre_save method, but this doesn't work properly. It actually results in an HTML response coming back from Django, rather than a message from the Django Rest Framework.
Use the django rest framework exceptions. For example:
from rest_framework.exceptions import ParseError
...
parsed_data = self.parse(some_data)
if not parsed_data:
raise ParseError('Some error occurred')
Also note that you won't see a 404 in there, that's because it uses the django.http.Http404 exception. These are returned by the API in a nice way.
Note:
If you are doing a significant amount of validation you might want to look at placing your logic in the serializer.
In my Django application, I have a forms.py file in which I define loads of classes corresponding to form input screens. Each of these classes does some validation either in that attribute/field specific _clean() functions or in the overall clean() function for the form class. If validation fails in any of these clean() functions, I raise an error like this:
raise forms.ValidationError('Invalid value dude!!')
When such an error is raised, the application catches the error and displays it on the form for the user.
I also have a logger defined at the top of this file like this:
import logging
logger = logging.getLogger(__name__)
Now, in addition to reporting to the user the ValidationErrors, I would like to catch them and log them as errors. Is there some generic and elegant way I can get the logger to log all such errors without changing any other behavior that affects the application's user?
You can extend your Forms to log the errors as soon as the validation ends:
class LoggingMixin(object):
def full_clean(self):
super(LoggingMixin, self).full_clean()
for field, errors in self.errors.iteritems():
logger.info('Form error in %s: %s', ', '.join(errors))
Then define your forms using the logging mixin:
class MyForm(LoggingMixin, forms.Form):
...
When Django 1.7 is out, you will also be able to catch the exceptions messages as they are raised. This will give you the raw exceptions as they have been raised (the Form does some more checking):
class LoggingMixin(object):
def add_error(self, field, error):
if field:
logger.info('Form error on field %s: %s', field, error)
else:
logger.info('Form error: %s', error)
super(LoggingMixin, self).add_error(field, error)
WARNING: Using add_error will do nothing in Django <= 1.6.
Django documentation says:
When DEBUG is False, Django will email the users listed in the ADMINS
setting whenever your code raises an unhandled exception and results
in an internal server error (HTTP status code 500).
But does this includes django admin site? And if not, how can I enable such reporting?
I'm asking this because when I intensionally rise an Exception at ModelAdmin subclass I receive no email.
On the other hand I tried to send manually and it works fine.
$ ./manage.py shell
>>> from django.core.mail import EmailMessage
>>> email = EmailMessage('Hello', 'World', to=['email#example.com'])
>>> email.send()
UPDATE:
Also Django does sends crash reports when exception rises at API part of application (driven by piston).
Any help is much appreciated.
There is nothing special about the admin site in this instance. Django will send you an email when an admin view raises an unhandled exception.
Troubleshooting idea 1
Have you tested whether you receive an email for a non-admin view? Could it be a permissions issue? The webserver might be running as a different user than when you test emailing from the shell.
Troubleshooting idea 2
Where in the ModelAdmin are you raising the exception?
The following example will not work, because the exception is raised when the ModelAdmin class is defined, not when the request is processed.
class MyModelAdmin(ModelAdmin):
raise Exception
Instead, raise the exception in a method. You should get an email for the following model, if you go to it's change view url (e.g /admin/app/mymodel/)
class MyModelAdmin(ModelAdmin):
def get_queryset(self, request, queryset):
raise Exception
In django-social-auth, there are a few instances where a back-end will raise a ValueError (such as when a user cancels a login request or if a user tries to associate with an account that's already been associated with another User). If a User runs into one of these scenarios, they'll be presented with a 500 error on your site.
So, what's the best way to catch these? I'd prefer to be able to display a useful message (via the messages framework) when this happens, but I'm at a loss as to the best way to do this.
I'm thinking about writing my own view (in a separate app) that just wraps social_auth's associate_complete view, but this seems clunky... Any ideas?
I could fork django-social-auth and customize this behavior, but I'd prefer not to maintain a separate fork - especially since I can't assume everone would want to handle these Exceptions in the same manner.
Rather old question but worth mention that recent version of DSA supports a custom exception processor where you can do whatever you want with the exception message. The default version stores them in the messages app.
Also the exceptions are differentiated now instead of the not-useful ValueError used. Check the docs http://django-social-auth.readthedocs.org/en/latest/configuration.html.
Update (13/08/2013):
Since I've posted the above things have changed, now DSA has an exception middleware that when enabled stores the exception message in the jango builtin messages app. It's preferable to subclass the middleware and add the custom behavior to it. Check the doc at http://django-social-auth.readthedocs.org/en/latest/configuration.html#exceptions-middleware
Sample middleware:
# -*- coding: utf-8 -*-
from social_auth.middleware import SocialAuthExceptionMiddleware
from social_auth.exceptions import AuthFailed
from django.contrib import messages
class CustomSocialAuthExceptionMiddleware( SocialAuthExceptionMiddleware):
def get_message(self, request, exception):
msg = None
if (isinstance(exception, AuthFailed) and
exception.message == u"User not allowed"):
msg = u"Not in whitelist"
else:
msg = u"Some other problem"
messages.add_message(request, messages.ERROR, msg)
I've ecountered the same problem and it seems, that creating wrapper view is the best way to handle this situation, at this point, atleast. Here is how I had mine done:
def social_auth_login(request, backend):
"""
This view is a wrapper to social_auths auth
It is required, because social_auth just throws ValueError and gets user to 500 error
after every unexpected action. This view handles exceptions in human friendly way.
See https://convore.com/django-social-auth/best-way-to-handle-exceptions/
"""
from social_auth.views import auth
try:
# if everything is ok, then original view gets returned, no problem
return auth(request, backend)
except ValueError, error:
# in case of errors, let's show a special page that will explain what happened
return render_to_response('users/login_error.html',
locals(),
context_instance=RequestContext(request))
You will have to setup url for it:
urlpatterns = patterns('',
# ...
url(r'^social_auth_login/([a-z]+)$', social_auth_login, name='users-social-auth-login'),
)
And then use it as before in template:
Log in with Google
Hope this helps, even aftern two months after question was asked :)
You need add social auth middleware:
MIDDLEWARE_CLASSES += ('social_auth.middleware.SocialAuthExceptionMiddleware',)
If any error occurs user will be redirected to erorr url(LOGIN_ERROR_URL from settings).
For detailed explanation please see documentation:
http://django-social-auth.readthedocs.org/en/latest/configuration.html#exceptions-middleware
In my app's views.py:
from social_auth.views import associate_complete
def associate_complete_wrapper(request, backend):
try:
return associate_complete(request, backend)
except ValueError, e:
if e and len(e.args) > 0:
messages.error(request, "Failed to Associate: %s" % e.args[0])
return redirect(reverse('pieprofile-edit-account'))
Then in the Root URLconf (notice the order of these url patterns):
url(r'^associate/complete/(?P<backend>[^/]+)/$', 'myapp.views.associate_complete_wrapper'),
url(r'', include('social_auth.urls')),
My associate_complete_wrapper url essentially hijacks social_auth's socialauth_associate_complete url.