Active Storage attachment is nil

[cseelus]

Using File Validators file_content_type and file_size with Active Storage throw a Module::DelegationError error (content_type delegated to attachment, but attachment is nil and size delegated to attachment, but attachment is nil), when a form for a Model thats being validated gets submitted without attaching a file.

The following workaround works for now:

validates :image, file_content_type: { allow: ['image/jpeg', 'image/png', 'image/gif'] }, if: -> { image.attached? }

This might fit into the README, should I open a PR?

[musaffa]

A PR is welcome. You should add some relevant tests for the failing scenarios.

[cseelus]

Just looked into your tests, seems like they use a tool called Appraisal that tests agains Active Model. Don't think can be reproduced w/o Active Storage, which in contrast to Active Model is not standalone afaik, also needs installation + db.

[musaffa]

In the PR, you will add some code to make it work. Those codes need tests. You can mock the external dependencies/method calls.

[EdwardIII]

@musaffa I've had a go at a PR on this:

#30

What do you think?

If there's no attachment, it fails validation properly due to not being a big enough file rather than raising an exception.