In Django what does the request argument in a method do?

Question

I have seen a few codes where sometimes the authenticate method have the request argument while other times it does not, e.g. see the below codes:

Code 1:

def register(request):
     
    if request.method == 'POST':
        form = UserCreationForm(request.POST)

        if form.is_valid():
            form.save()
            # code for automatic login after singing up
            username = form.cleaned_data['username']
            password = form.cleaned_data['password1']
            user = authenticate(username=username, password=password)
            login(request, user)
            return redirect('/')

Code 2:

def login(request):
     
    if request.method == 'POST':
        username = request.POST['username']
        password = request.POST['password']
        user = authenticate(request, username=username, password=password)

According to the official docs:

request is an HttpRequest and maybe None if it wasn’t provided to authenticate() (which passes it on to the backend).

What does this request argument actually do and when should I consider passing it in the authenticate method?

Answer 1

According to the Django docs, and confirmed by me just now looking at the source, this is passed to the authenticate method of whatever authentication backend you are using.

The only backend class that seems to use it is the RemoteUserBackend, and the reason for this is because RemoteUserBackend will create a local User model instance the first time a user (who already exists in the remote auth database) logs in, and then, before returning the user instance, the backend calls its own configure_user method, passing the new user instance, along with request.

Docs for that here: https://docs.djangoproject.com/en/3.1/ref/contrib/auth/#django.contrib.auth.backends.RemoteUserBackend

But, here's where it gets silly.. is that, the default implementation of configure_user doesn't actually do anything, it's just a stub that you can extend in a subclass of RemoteUserBackend that you may choose to write if you want to add your own behavior to it.

Clear as mud. But really it makes sense. Perhaps some parameters were passed in the request that triggered the need for authentication, and some of those parameters contain information about the user that needs be stored in the newly created User instance... The request object contains everything known about the request, it comes in handy.

Suffice to say that somebody, some time, either wrote an auth backend that required access to the request at this point, or the author of the auth module anticipated that someone might need it some day. But in the auth module itself, by default, request is not used for anything that I can see.

So it doesn't seem necessary to pass request to authenticate, but if you can imagine that in the future you might want to configure your application with a funky authentication backend, you might want to pass it.. just in case it's needed by that backend. The default ModelBackend doesn't use it.