Presentable Exceptions

This is a module for django restframework, in which modules can specifiy exceptions in an extra file with an key an description. At some place in the code, they can be fetched by the package and key and bubble up to the view. Here a mixin detects them and creates a proper response for an fat-client, which can show them then to to user - thus the exceptions are presentable.

Getting started

Say, you have a module, like auth_api which is registered in INSTALLED_APPS in the Django settings.py. Create a new file auth_api/presentable_exceptions.py with this content

presentable_exceptions = {
    'client': [
        ('not-enough-data-to-delete-user', 'You did not provide enough data, that we can delete the user {username}')
    ],
    'server': [
        ('backend-connection-lost', 'We lost the connection to the backend'),
    ]
}

This file can be in every module and consists of two parts: The exceptions, that are the clients fault and the exceptions that are our fault. The first will cause a 4xx error, the latter a 5xx.

Say, you have now an View somewhere, like that:

class MeView(WithPresentableException, APIView):

    def get(self, request):
        data = some_function_with_a_deep_call_stack()
        return Response(data)

This will call multiple function and somewhere there is the function boom() called:

def boom():
    raise PresentableException.of('auth_api', 'backend-connection-lost')


def some_function_with_a_deep_call_stack():
    # ...
    boom()
    # ...

This PresentableException will be an PresentableServerException and bubble up into the Mixing WithPresentableException specified in the view above, which generates a proper response (with a 5xx code in this case).