Minitest::UnexpectedError: TypeError: no implicit conversion from nil to integer

[przbadu]

Describe the bug

Model code

validates_attachment :logo, content_type: { content_type: %w[image/jpg image/jpeg image/gif image/png] }
  validates_attachment_size :logo, less_than: 5.megabytes, message: 'Max allowed attachment size is 5MB'
  validates_attachment_presence :logo

Test case:

FactoryGirl.create(:payment_provider, logo: File.new('test/fixtures/ofx-logo.png'))

To Reproduce
Steps to reproduce the behavior:

1. I am upgrading my legacy Rails app which was originally built with Rails 4.2 to Rails 5.2.8
2. We migrated our paperclip to kt-paperclip during rails 5 upgrade and been running it for years without any issue. It worked well till Rails 5.1.x.
3. As soon as I upgraded Rails version to 5.2.8 I am getting given error Minitest::UnexpectedError: TypeError: no implicit conversion from nil to integer

Expected behavior
It should create uploads

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: Ubuntu 20.20
• Browser [e.g. chrome, safari]
• Version kt-paperclip-6.4.1

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

[przbadu]

So the problem was because of net-protocol gem not actually directly related with paperclip.

The fix was to downgrade net-protocol from 0.2.2 to 0.1.1.

gem 'net-protocol', '~> 0.1.0'

Also note that, it is happening on ruby version 3.0.x and rails version 6.1.x combination.