Marshall.dump TypeError: can't dump hash with default proc with Rails 5

[jvenezia]

Rails 5 introduces model.errors.details rails/rails#18322

When creating a model instance with facotry_girl, it is impossible to dump it:

Marshal.dump FactoryGirl.create :user
# => TypeError: can't dump hash with default proc

You can test this with Rails 3&4 thanks to this gem https://github.com/cowbell/active_model-errors_details .

Without this Rails 5 feature or this gem it works fine.

[jvenezia]

Just realised the problem is from Rails. I'm moving the issue, sorry.