Problem testing user is None when extending auth backend.

[graeme]

In a custom authentication backend, I was getting this error with this (previous developer's!) code:

   if user.is_authenticated() and user.is_staff:
AttributeError: 'NoneType' object has no attribute 'is_authenticated'

The cause seemed clear, the parent classes method was run first with super and returned None when it failed to authenticate, so I tried to fix by testing whether user is None, but I still get this:

if (user is not None) and user.is_authenticated() and user.is_staff:
AttributeError: 'NoneType' object has no attribute 'is_authenticated'

I am probably missing something obvious, but if user is None, only (user is not None) will be evaluated there should be no error, if user is not None, I should not have a NoneType in the error.

[Derek]

Note that

user.is_authenticated()

has become

user.is_authenticated

in Django 1.10

Otherwise if user is really (or could really) be None, then try... except may be better:

try:
    if user.is_authenticated() and user.is_staff:
        do something
    else:
        do something else 
except AttributeError as err:
    log.error('User not found:%s' % err)

[graeme]

On Thursday, September 28, 2017 at 2:16:44 PM UTC+1, Derek wrote:

Note that

user.is_authenticated()

has become

user.is_authenticated

in Django 1.10

 

Still on 1.8 in this case

Otherwise if user is really (or could really) be None, then try... except may be better:

 

Thanks, will try it. I still do not understand why checking for not None does not work as I expected.

Importing the code into the Django shell and calling authenticate() with an invalid username/password combination works as expected