Django Authentication Form not working properly

I am trying to create a very basic login system (just to grasp Django's authentication system, nothing fancy).

Thing is, when I use the following code (i.e. don't validate authentication form submission), everything works perfectly.

The views.py file:

from django.shortcuts import render, redirect
from django.http import request
from django.contrib.auth.decorators import login_required
from .forms import UserRegistrationForm
from django.contrib import messages
from django.contrib.auth import authenticate, login, logout
from django.contrib.auth.forms import AuthenticationForm

@login_required(login_url="accounts/login")
def home(request):
    return render(request, "main/home.html")

def register_user(request):
    if request.method == "POST":
        reg_form = UserRegistrationForm(request.POST)
        if reg_form.is_valid():
            user = reg_form.save()

            messages.success(request, f'You have successfully registered!')
            return redirect("login")
        else:
            messages.error(request, "Some problem occured")
    else:
        reg_form = UserRegistrationForm()
    return render(request, template_name='main/register.html', context={"form":reg_form})
    
def login_view(request):
    if request.method == "POST":
        username = request.POST.get("username")
        password = request.POST.get("password")
        user = authenticate(request, username = username, password = password)

        if user is not None:
            login(request, user)
            messages.success(request, f"You logged in as: {username}")
                    
            return redirect("home")
        else:
            messages.error(request, "Invalid username or password")
            return redirect("login")
    else:
        auth_form = AuthenticationForm()
    return render(request, "registration/login.html", context={"form":auth_form})

def logout_request(request):
    logout(request)
    messages.success(request, f"You have logged out.")
    return redirect("login")

However, when I insert authentication form validation and population, user is not authenticated and None is returned instead.

For the purpose of simplicity I am adding the 'login_view' only as this is where I encounter the problem.

def login_view(request):
    if request.method == "POST":
        auth_form = AuthenticationForm(request.POST)
        if auth_form.is_valid():
            username = auth_form.cleaned_data.get("username")
            password = auth_form.cleaned_data.get("password")
            user = authenticate(request, username = username, password = password)

            if user is not None:
                login(request, user)
                messages.success(request, f"You logged in as: {username}")
                    
                return redirect("home")
            else:
                messages.error(request, "Invalid username or password")
                return redirect("login")
        else:
            messages.error(request, f"Some problem encountered.")
            return redirect("login")
    else:
        auth_form = AuthenticationForm()
    return render(request, "registration/login.html", context={"form":auth_form})

NOTE: I know such an if-else ladder is discouraged and shouldn't be used. But I'm just curious as to why the former solution works and the latter one does not.

Thanks for the help.

The Django AuthenticationForm takes a request object as its first argument. You can provide submitted data like request.POST as the data kwarg

auth_form = AuthenticationForm(None, data=request.POST)