I have a model / Form / view for a request that works well, but when I want to update a request all the fields are loaded except the due_date field (with a date widget) witch remains empty. If I don’t pay attention I validate and the due_date become None. I would like it to load the date that was saved during creation by default and then I modify it or not. Here is the code.

Model

class Request(models.Model):
    thematic = models.ForeignKey(
        Thematic,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        verbose_name="Thématique",
    )
    context = models.ForeignKey(
        Context,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        verbose_name="Contexte",
    )
    technical_element = models.CharField(
        max_length=255, verbose_name="Élément technique", blank=True, null=True
    )
    due_date = models.DateField(verbose_name="Date d'échéance", blank=True, null=True)

    def __str__(self):
            return self.context

    class Meta:
        verbose_name = "Request"
        verbose_name_plural = "Requests"

Forms

class RequestForm(forms.ModelForm):
    new_thematic = forms.CharField(
        max_length=255, required=False, label="New Thematic"
    )
    new_context = forms.CharField(
        max_length=255, required=False, label="New Context"
    )
    due_date = forms.DateField(
        widget=forms.DateInput(attrs={"type": "date"}),
        required=False,
    )

    class Meta:
        model = Demande
        fields = "__all__"
        widgets = {
            "thematic": forms.Select(attrs={"class": "form-control"}),
            "context": forms.Select(attrs={"class": "form-control"}),
            "technical_element": forms.TextInput(attrs={"class": "form-control"}),
            "due_date": forms.DateInput(
                attrs={"class": "form-control", "type": "date"}
            ),
        }

    def __init__(self, *args, **kwargs):
        super(DemandeForm, self).__init__(*args, **kwargs)
        if "instance" in kwargs:
            instance = kwargs["instance"]
            if instance.due_date:
                self.fields["due_date"].initial = instance.due_date
        self.fields["thematic"].queryset = Thematic.objects.all()
        self.fields["context"].queryset = Context.objects.all()

    def save(self, commit=True):
        instance = super(DemandeForm, self).save(commit=False)
        new_thematic_name = self.cleaned_data.get("new_thematic")
        new_context_description = self.cleaned_data.get("new_context")

        if new_thematic_name:
            thematic, created = Thematic.objects.get_or_create(name=new_thematic_name)
            instance.thematic = thematic

        if new_context_description:
            context, created = Context.objects.get_or_create(
                description=new_context_description
            )
            instance.context = context

        if commit:
            instance.save()
        return instance

Views

class UpdateRequestView(View):
    def get(self, request, pk):
        request_instance = get_object_or_404(Request, pk=pk)
        request_form = RequestForm(instance=request_instance)
        return render(
            request,
            "operation/update_request_form.html",
            {
                "request_form": demande_form,
                "request_instance": request_instance,
                "title": f"Modify the request {request_instance.context}",
            },
        )

    def post(self, request, pk):
        request_instance = get_object_or_404(Request, pk=pk)
        request_form = RequestForm(request.POST, instance=request_instance)
        if request_form.is_valid():
            instance = request_form.save(commit=False)
            due_date = request_form.cleaned_data.get("due_date")
            if due_date:
                instance.due_date = due_date
            instance.save()
            messages.success(request, "The request was successfully updated.")
            return redirect(reverse("drequest_detail", args=[instance.id]))
        else:
            for field, errors in request_form.errors.items():
                for error in errors:
                    messages.error(request, f"Error {field}: {error}")
        return render(
            request,
            "operation/update_request_form.html",
            {
                "request_form": demande_form,
                "request_instance": request_instance,
                "title": f"Modify the request {request_instance.context}",
            },
        )

In the POST part I have already tried something to display the value of due_date but it does not work.

I tried the init in the form part and another solution in the post part of the view.