Django Form with validation state for unique - django

Question

I try to add a validation state like "this already exist." (like registration form, see picture) just under my form input.
But when I submit my form i'v this error 'UNIQUE constraint failed'
this is my code
model
class Company(models.Model):
user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
siret = models.CharField(max_length=50, unique=True)
forms
class CheckoutForm(forms.Form):
siret = forms.CharField(required=True, widget=forms.TextInput(attrs={'placeholder': 'Ton SIRET'}))
class Meta:
model = Company
fields = ('siret')
def clean(self):
siret = cleaned_data.get('siret')
if siret:
raise forms.ValidationError("This siret exist.")
else:
return siret
view
def post(self, request, *args, **kwargs):
form = CheckoutForm(self.request.POST)
if form.is_valid():
siret = form.cleaned_data.get('siret')
company = Company(
user = self.request.user,
siret = siret,
)
company.save()
context = {
'company': company,
}
return redirect("core:payment")
else:
messages.info(self.request, "Please fill in the shipping form properly")
return redirect("core:checkout")
template
{% load crispy_forms_tags %}
<main>
<div class="container wow fadeIn">
<h2 class="my-5 h2 text-left">Checkout form</h2>
<div class="row">
<div class="col-md-8 mb-4">
<div class="card">
<form method="post" class="card-body">
{% csrf_token %}
{{ form|crispy }}
<button class="btn btn-primary" id="checkout-button" data-secret="{{ session_id }}">
Checkout
</button>
</form>
</div>
</div>
Thanks a lot

Answer 1

you have to add errors_messages to your email field like this:
email = models.EmailField(
_('email address'),
blank=True,
unique=True,
null=True,
error_messages={
'unique': _("A user with that email address already exists."),
}
)