How to solve "NOT NULL constraint failed: mainapp_cartproduct.user_id" error?

Question

Django

Hello! After I added registration to the site, an error began to appear when adding goods to the cart
IntegrityError at /add-to-cart/Interior_paints1/
NOT NULL constraint failed: mainapp_cartproduct.user_id

The error appears exactly if the user is not authorized on the site, if you log in, then the error immediately same disappears.

forms.py

class LoginForm(forms.ModelForm):

    password = forms.CharField(widget=forms.PasswordInput)

    class Meta:
        model = User
        fields = ['username', 'password']

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.fields['username'].label = 'Логин'
        self.fields['password'].label = 'Пароль'

    def clean(self):
        username = self.cleaned_data['username']
        password = self.cleaned_data['password']
        if not User.objects.filter(username=username).exists():
            raise forms.ValidationError(f'Пользователь с логином "{username} не найден в системе')
        user = User.objects.filter(username=username).first()
        if user:
            if not user.check_password(password):
                raise forms.ValidationError("Неверный пароль")
        return self.cleaned_data


class RegistrationForm(forms.ModelForm):

    confirm_password = forms.CharField(widget=forms.PasswordInput)
    password = forms.CharField(widget=forms.PasswordInput)
    phone = forms.CharField(required=False)
    address = forms.CharField(required=False)
    email = forms.EmailField(required=True)

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.fields['username'].label = 'Логин'
        self.fields['password'].label = 'Пароль'
        self.fields['confirm_password'].label = 'Подтвердите пароль'
        self.fields['phone'].label = 'Номер телефона'
        self.fields['first_name'].label = 'Имя'
        self.fields['last_name'].label = 'Фамилия'
        self.fields['address'].label = 'Адрес'
        self.fields['email'].label = 'Электронная почта'

    def clean_email(self):
        email = self.cleaned_data['email']
        domain = email.split('.')[-1]
        if domain in ['com', 'net']:
            raise forms.ValidationError(
                f'Регистрация для домена {domain} невозможна'
            )
        if User.objects.filter(email=email).exists():
            raise forms.ValidationError(
                f'Данный почтовый адрес уже зарегистрирован в системе'
            )
        return email

    def clean_username(self):
        username = self.cleaned_data['username']
        if User.objects.filter(username=username).exists():
            raise forms.ValidationError(
                f'Имя {username} занято'
            )
        return username

    def clean(self):
        password = self.cleaned_data['password']
        confirm_password = self.cleaned_data['confirm_password']
        if password != confirm_password:
            raise forms.ValidationError('Пароли не совпадают')
        return self.cleaned_data

    class Meta:
        model = User
        fields = ['username', 'password', 'confirm_password', 'first_name', 'last_name', 'address', 'phone', 'email']

views.py

class LoginView(CartMixin, View):

    def get(self, request, *args, **kwargs):
        form = LoginForm(request.POST or None)
        categories = Category.objects.all()
        context = {
            'form': form,
            'categories': categories,
            'cart': self.cart
        }
        return render(request, 'login.html', context)

    def post(self, request, *args, **kwargs):
        form = LoginForm(request.POST or None)
        if form.is_valid():
            username = form.cleaned_data['username']
            password = form.cleaned_data['password']
            user = authenticate(
                username=username, password=password
            )
            if user:
                login(request, user)
                return HttpResponseRedirect('/')
        categories = Category.objects.all()
        context = {
            'form': form,
            'cart': self.cart,
            'categories': categories
        }
        return render(request, 'login.html', context)


class RegistrationView(CartMixin, View):

    def get(self, request, *args, **kwargs):
        form = RegistrationForm(request.POST or None)
        categories = Category.objects.all()
        context = {
            'form': form,
            'categories': categories,
            'cart': self.cart
        }
        return render(request, 'registration.html', context)

    def post(self, request, *args, **kwargs):
        form = RegistrationForm(request.POST or None)
        if form.is_valid():
            new_user = form.save(commit=False)
            new_user.username = form.cleaned_data['username']
            new_user.email = form.cleaned_data['email']
            new_user.first_name = form.cleaned_data['first_name']
            new_user.last_name = form.cleaned_data['last_name']
            new_user.save()
            new_user.set_password(form.cleaned_data['password'])
            new_user.save()
            Customer.objects.create(
                user=new_user,
                phone=form.cleaned_data['phone'],
                address=form.cleaned_data['address']
            )
            user = authenticate(
                username=new_user.username, password=form.cleaned_data['password']
            )
            login(request, user)
            return HttpResponseRedirect('/')
        categories = Category.objects.all()
        context = {
            'form': form,
            'categories': categories,
            'cart': self.cart
        }
        return render(request, 'registration.html', context)

Please explain how I can make it possible for anonymous users to add goods to the cart.

Answer 1

Where is the mainapp_cartproduct model?
If I understand correctly, then the model in the user field cannot have a NULL value, but it tries to be installed there for unauthorized people
. According to your problem:
https://ru.stackoverflow.com/questions/803293/%D0%...
https: //stackoverflow.com/questions/42960271/not-n...
https://stackoverflow.com/questions/46512639/not-n...