How to display validation error message for FileField?

• Package version:1.7.2
• Django version:2.1
• Python version:3.7
• Template pack: Bootstrap4

I have a FileField in my model and I implemented Django’s FileExtensionValidator, as well as my own custom field validator to check the file size. It works, but crispy-forms doesn’t display error message when these validations fail.

Model

from django.core.validators import FileExtensionValidator

class Project(models.Model):
    owner = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name='projects',
    )
    title = models.CharField(
        _('project name'),
        max_length=100,
        help_text=_('Required. 100 characters or fewer.'),
    )
    slug = models.SlugField(
        _('slug'),
        max_length=80,
    )
    created = models.DateTimeField(
        _('dateTime created'),
        auto_now_add=True,
    )
    xmlfile = models.FileField(
        _('input file'),
        upload_to=user_directory_path,
        validators=[FileExtensionValidator(allowed_extensions=('xml',))],
        help_text=_('Required. Please upload an XML file.'),
    )

Form

from django.core.exceptions import ValidationError

def file_size(value):
    limit = 9 * 1024 * 1024
    if value.size > limit:
        raise ValidationError('File too large. Size should not exceed 9 MiB.')

class ProjectForm(forms.ModelForm):

    xmlfile = forms.FileField(
        label='XML File Upload',
        widget=forms.FileInput(attrs={'accept':'application/xml'}),
        validators=[file_size],
    )

    class Meta:
        model = Project
        widgets = {
            'owner': HiddenInput(),
        }

Template

{% block content %}
    <h1>New Project</h1>
    <form action="" method="post" enctype="multipart/form-data">{% csrf_token %}
      {{ form|crispy }}
      <input type="submit" value="Create" />
    </form>
{% endblock content %}

View

class ProjectCreate(CreateView):
    form_class = ProjectForm
    model = Project
    template_name = 'project_new.html'
    success_url = reverse_lazy('my_projects_list')

    def get_initial(self):
        initial = super().get_initial()
        initial['owner'] = self.request.user
        return initial

When trying to upload an XML file less than 9M, it works and the user is brought to the success URL. But when either file format or file size is wrong, it’s correct that we continue to stay on the page of project_new.html, but no error message is displayed on this page related to FileExtensionValidator or file_size().

When I change {{ form|crispy }} to {{ form.as_p }} , the validation error will be displayed on the screen. Do you know how to display validation error messages when using {{ form|crispy }}? Thank you!

[StevenMapes]

This is a work around. You need to add the following CSS class overload to your projects CSS.

.invalid-feedback {
    display: initial;
}```

The default invalid-feedback which has a` display:None` so the errors messages are added to the DOM but do not appear so this overloads it.

The BS4 resource for .invalid feedback is [Form Styles](https://getbootstrap.com/docs/4.0/components/forms/)

[jennyd1]

This is a work around. You need to add the following CSS class overload to your projects CSS.

.invalid-feedback {
    display: initial;
}```

The default invalid-feedback which has a` display:None` so the errors messages are added to the DOM but do not appear so this overloads it.

The BS4 resource for .invalid feedback is [Form Styles](https://getbootstrap.com/docs/4.0/components/forms/)

Thank you, after searching so many resources, and going over my code to try and find the error, this resolution resolved my issue.