ActionController::InvalidAuthenticityToken Rails 5 / Devise / Audited / PaperTrail gem

Question

Background Details

I am using Devise for authentication to login to a Rails 5 application.

Whenever I bundle either the Audited or Paper Trail gem, when I attempt to #create a new session (via the sign in form - /users/sign_in), I receive the following error:

ActionController::InvalidAuthenticityToken

Environment Details

Ruby 2.3.1

Gems:

• rails 5.0.2
• devise => 4.2.1
• paper_trail => 7.0.1

Steps to Reproduce:

1. Create Rails 5 application
2. Add Devise gem
3. Add Audited or Paper Trail gem
4. Attempt to login

Answer 1

As it turns out, Devise documentation is quite revealing with regard to this error:

For Rails 5, note that protect_from_forgery is no longer prepended to the before_action chain, so if you have set authenticate_user before protect_from_forgery, your request will result in "Can't verify CSRF token authenticity." To resolve this, either change the order in which you call them, or use protect_from_forgery prepend: true.

The fix was to change code in my application controller from this:

 protect_from_forgery with: :exception

To this:

 protect_from_forgery prepend: true

This issue did not manifest itself until I attempted adding Audited or Paper Trail gems.