Authentication Form not working properly.

Using Django Forms & APIs
1

Hello.

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.

2

It will help you diagnose the errors you are encountering if you print (or render) the errors reported by the form from the is_valid test. See the Form.errors docs.

3

Ok. So, I entered the print statement (using auth_form.errors.get_data() ) in both the ‘is_valid’ section and the corresponding else statement. It just gives me ‘{}’.

Also, when I insert a print statement in the is_valid section to print the entered username, nothing is printed. And when I add this statement in the corresponding else, the correct username gets printed.

4

Please post the updated code where you’re trying all this. (I don’t see a get_data method, I see an as_data and a get_json_data, so I would actually expect you to get an error message if that’s what you tried.)

5

Also note that the clean method of the django.contrib.auth.forms.AuthenticationForm performs the authenticate call - that’s not something you need to do within your view. It also raises its own error messages internally.

I suggest you review how that form works - you’re doing a lot of work here that is trying to replicate what that form already provides.

6

Yes, I mistook its working to be the same as other Model Forms.

It provides its own authentication mechanism and generates its own errors.

Also, it takes a request parameter (mandatory) and after that we can pass request.POST as data (using kwargs).

Thanks loads for the help :slight_smile: