how to display models.full_clean() ValidationError in django admin?

Question

https://docs.djangoproject.com/en/4.0/ref/models/instances/#validating-objects

from django.core.exceptions import ValidationError
try:
    article.full_clean()
except ValidationError as e:
    # Do something based on the errors contained in e.message_dict.
    # Display them to a user, or handle them programmatically.
    pass

There tell us can Display them to a user, how to display errors in Admin?

When I do nothing:

• When Settings.py Debug = True, it always render a ValidationError at /admin/xxx/xxx/xxx/change/ page.
• When Settings.py Debug = False, it always render a HTTP 500 page.

Some code in models.py:

    def clean(self):
        try:
            if self.get_previous_state:
                if self.get_previous_state.state_choice == self.state_choice and \
                        self.get_previous_state.state_location == self.state_location:
                    raise ValidationError({"state_choice": f"提交的状态与当前状态冲突({self.product_entity.rfidtag.EPC_bank})"},
                                          params={'state_choice': self.state_choice})
        except Exception as e: # except the RelatedObjectDoesNotExist Exception to ValidationError
            raise ValidationError(e)

    def save(self, force_insert=True, *args, **kwargs):
        self.pk = None  # force_insert 具有 pk unique 限制
        self.previous_state = self.get_previous_state
        self.full_clean()
        super(ProductEntityState, self).save(force_insert=True, *args, **kwargs)

sucess condition

error condition

Answer 1

What is the context of that code? Django will automatically show the errors for you in the admin when creating/editing the object through the admin. You don't have to manually call full_clean() as the auto-generated ModelForm from the admin will do so.

Answer 2

I fixed this bug by myself.

Because django admin just call formsets.all_valid() to validtion in ModelAdmin._changeform_view().

ModelAdmin._changeform_view() uses transaction.atomic().

When formsets.all_valid(), the froms which will be deleted didn't be commit.

Now, the previous state is the instance which will be deleted.It will not raise the ValidationError, the formsets.all_valid() will return True.

So ModelAdmin._changeform_view() will call from.instance.save() in foreach formsets.

This time, the previous state was be changed. So it will raise the ValidationError.

But ModelAdmin._changeform_view() didn't expect ValidationError in ModelAdmin.save_related(). it will expect by django\core\handlers\exception.py and call response_for_exception().

I cover the ModelAdmin._create_formsets() and fill the previous_state in all formsets.instance.

Notice: when you get form, you should watch which model not call the model.clean(), I use form.changed_data to get instance.

Then, when ModelAdmin._create_formsets() call formsets.all_valid(). It will return False, and raise ValidationError in your page.