Django Forms Validation message not showing - django

Question

I'm trying to restrict file type, size and extension that can be uploaded in a form. The functionality seems to work, but the validation error messages are not showing. I realize that if file._size > 4*1024*1024 is probably not the best way - but I'll deal with that later.
Here's the forms.py:
class ProductForm(forms.ModelForm):
class Meta:
model = Product
fields = ['name', 'description', 'url', 'product_type', 'price', 'image', 'image_url', 'product_file']
labels = {
'name': 'Product Name',
'url': 'Product URL',
'product_type': 'Product Type',
'description': 'Product Description',
'image': 'Product Image',
'image_url': 'Product Image URL',
'price': 'Product Price',
'product_file': 'Product Zip File',
}
widgets = {
'description': Textarea(attrs={'rows': 5}),
}
def clean(self):
file = self.cleaned_data.get('product_file')
if file:
if file._size > 4*1024*1024:
raise ValidationError("Zip file is too large ( > 4mb )")
if not file.content-type in ["zip"]:
raise ValidationError("Content-Type is not Zip")
if not os.path.splitext(file.name)[1] in [".zip"]:
raise ValidationError("Doesn't have proper extension")
return file
else:
raise ValidationError("Couldn't read uploaded file")
...and here's the view I'm using for that form:
def post_product(request):
# if this is a POST request we need to process the form data
if request.method == 'POST':
# create a form instance and populate it with data from the request:
form = ProductForm(data = request.POST, files = request.FILES)
# check whether it's valid:
if form.is_valid():
# process the data in form.cleaned_data as required
product = form.save(commit = False)
product.user = request.user
product.likes = 0
product.save()
# redirect to a new URL:
return HttpResponseRedirect('/products')
What am I missing?

Answer 1

In your view, you are doing a redirect regardless of whether or not the form is valid - so there is nowhere for Django to show form errors.
The normal way to do this would be to re-render the form when is_valid() is False:
if form.is_valid():
# process the data in form.cleaned_data as required
product.save()
# redirect to a new URL - only if form is valid!
return HttpResponseRedirect('/products')
else:
ctx = {"form": form}
# You may need other context here - use your get view as a template
# The template should be the same one that you use to render the form
# in the first place.
return render(request, "form_template.html", ctx}
You may want to consider using a class-based FormView for this, as it handles the logic of re-rendering forms with errors. This is simpler and easier than writing two separate get and post views to manage your form. Even if you don't do that, it will be easier to have a single view that handles both GET and POST for the form.