Passing :allow_blank option raises

[joelmoss]

I am trying to allow a blank attachment during validation...

has_one_attached :photo
validates :photo, attached: true, on: %i[create update], allow_blank: true,
                    content_type: { in: %r{\Aimage/.*\z}, message: :image_content_type_invalid },
                    size: { less_than: 5.megabytes }

But it fails with...

ArgumentError: You cannot pass the :allow_blank option to this validator (ArgumentError)

I can see in the code that the allow_blank option is supported, so why does this not work?

thankyou

[Mth0158]

Hi @joelmoss
The error comes from the attached validator (https://github.com/igorkasyanchuk/active_storage_validations/blob/master/lib/active_storage_validations/attached_validator.rb). It does not accept the allow_blank option when activated, since it requires to attach. It would be contradictory to require to attach something and to allow not to attach something, therefore the error.
Maybe the solution is to remove the attached: true validator?

[Mth0158]

I am pushing a quick MR to make the message clearer for future users

[Polo2]

👋 here, and thanks for the gem.

I'm also wondering about allowing optional attachement and I went to this issue.
I understand with your answer that removing attached: true would work to keep attachement optional.

But it's not very easy to read and guess for other developpers:

for example with this line:
validates :logo, content_type: [...]
it's not super clear that logo is optional.

Instead of adding a comment in our code everywhere optional attachements are validated,
Would it work too by adding explicit attached: false, or attached: nil?

Or should I go to
validates :logo, content_type: [...], allow_blank: true
(no attached validator, but allow_blank allowed in this case?)

thanks in advance for your answer, if you want I can open a tiny PR on ready to highlight this usecase.

[Mth0158]

Hi from Lyon @Polo2 👋

We could develop something like attached: false, but I think it's not the best option here.

ActiveStorage has_one_attached / has_many_attached association methods, like ActiveRecord has_one and have_many, by default allow to have empty child / children relation. It implicitly "implies" the allow_nil / allow_blank options.

You could write your association with one of these to make you code more explicit. All the gem validators, expect the attached one, allow these options (check our tests at https://github.com/search?q=repo%3Aigorkasyanchuk%2Factive_storage_validations+WorksWithAllRailsCommonValidationOptions&type=code).

I think it's by far the simplest & clearer option, but I am open to discussion :)