[FIXED] why doesn't the clean method see field in forms?

Issue

I'm facing an issue with my forms in Django. I've created something like this:

class EventForm(forms.ModelForm):
    class Meta:
        model = Event
        fields = [
            "name",
            "start_date",
            "end_date"
         
        ]

    def clean(self):
        start_date = self.cleaned_data["start_date"]
        end_date = self.cleaned_data["end_date"]
        if start_date > end_date:
            raise ValidationError("Start Date cannot be great than End Date")
        elif start_date == end_date:
            raise ValidationError("The dates must be different.")

    def clean_start_date(self):
        start_date = self.cleaned_data["start_date"]
        if timezone.now() > start_date:
            raise ValidationError("The start date of the event must be after today.")
        return start_date

When I tried to test it, something weird is happening. So, when I tried to input a start_date that is after today, I get the following message: start_date = self.cleaned_data["start_date"] KeyError: 'start_date' It looks like clean() doesn't see the start_date. But why?

Solution

clean happens after custom clean_<field_name> methods. Your clean_start_date raised a ValidationError, so the value for start_date was rejected and not included in cleaned_data.

Here is the relevant Django code:

    def full_clean(self):
        """
        Clean all of self.data and populate self._errors and self.cleaned_data.
        """
        self._errors = ErrorDict()
        if not self.is_bound:  # Stop further processing.
            return
        self.cleaned_data = {}
        # If the form is permitted to be empty, and none of the form data has
        # changed from the initial data, short circuit any validation.
        if self.empty_permitted and not self.has_changed():
            return

        self._clean_fields()  # <---  clean_start_date is called here
        self._clean_form()  # <--- clean is called in here
        self._post_clean()

    def _clean_fields(self):
        for name, bf in self._bound_items():
            field = bf.field
            value = bf.initial if field.disabled else bf.data
            try:
                if isinstance(field, FileField):
                    value = field.clean(value, bf.initial)
                else:
                    value = field.clean(value)
                self.cleaned_data[name] = value
                if hasattr(self, "clean_%s" % name):
                    value = getattr(self, "clean_%s" % name)()  # <--- your clean method raises a ValidationError
                    self.cleaned_data[name] = value
            except ValidationError as e:
                self.add_error(name, e) #  <--- except is triggered; 'start_date' never added to cleaned_data

Answered By - CoffeeBasedLifeform