Call Django's authenticate function with the request object

[jgeerds]

Description

As of Django 1.11 the authenticate function accepts a request as an
additional argument. This commit fixes compatibility between newer Django
versions and custom authentication backends which already depend on the request
object.

See also:

Django 1.11 release

authenticate() now passes a request argument to the authenticate() method of
authentication backends. Support for methods that don’t accept request as the
first positional argument will be removed in Django 2.1.

• tox (with all python versions) succeeds

[tomchristie]

Great stuff, thanks!
Could you explain if and how this works pre-1.11?
The call to authenticate still includes request=... in that case, will that still work okay, and are there cases in which it might fail (eg. custom auth backends?)

Thanks again, looks good.

[jgeerds]

Django 1.8.x, 1.9.x and 1.10.x releases use the following function signature:

def authenticate(**credentials):

This implies that it is not possible to use positional keyword arguments with this function:

In [7]: def authenticate(**credentials):
   ...:     print(credentials)
   ...: 

In [8]: authenticate('foo', 'bar')
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-8-b0a7d48cf507> in <module>()
----> 1 authenticate('foo', 'bar')

TypeError: authenticate() takes 0 positional arguments but 2 were given

In [9]: authenticate(username='foo', password='bar')
{'password': 'bar', 'username': 'foo'}

In [10]: 

I think this is also the reason why Django 1.11 introduced request as a keyword argument as well (at least until 2.1 comes out). Passing an extra request parameter works fine with pre-1.11:

In [12]: def authenticate(**credentials):
    ...:     print(credentials)
    ...: 

In [13]: authenticate(request='req', username='foo', password='bar')
{'request': 'req', 'password': 'bar', 'username': 'foo'}

However, from a custom auth backend perspective I think it might fail because of this:

    for backend, backend_path in _get_backends(return_tuples=True):
        try:
            inspect.getcallargs(backend.authenticate, **credentials)
        except TypeError:
            # This backend doesn't accept these credentials as arguments. Try the next one.
continue

I'll create a wrapper function in compat.py to handle old versions

[tomchristie]

Milestoning for 3.7 - looks like we ought to have this in now.
Anyone else want to review?

[carltongibson]

This looks great.