Devise raises error with Rails 4.2 upgrade

Question

When I run rails s:

/Users/galli01anthony/.rvm/gems/ruby-2.1.3/gems/devise-3.2.4/lib/devise/rails/routes.rb:455:in `ensure in with_devise_exclusive_scope': undefined method `merge!' for #<ActionDispatch::Routing::Mapper::Scope:0x007f8743e19020> (NoMethodError) 

When I run rake db:reset or db:migrate or db:setup:

rake aborted! NoMethodError: undefined method `merge!' for #<ActionDispatch::Routing::Mapper::Scope:0x007fca8d3f2780> 

Answer 1

It seems like the issue was fixed with this PR https://github.com/plataformatec/devise/pull/3153 a while ago. Update the devise gem in your application (if possible).

Change the version of devise in your Gemfile to at least 3.4.0:

gem 'devise', '~> 3.4.0'   # or later 

Then run:

bundle update devise 

---

Update: Devise was updated to version 3.5.x a while ago and 4.0 will be released soon (see all version on RubyGems.org). That said you may want to define at least a version 3.5.x in your Gemfile:

gem 'devise', '~> 3.5.0' 

Or just load the newest version that is possible:

gem 'devise', '> 3.4' 

follow by a bundle update devise

Answer 2

recently updated https://github.com/plataformatec/devise/pull/3153#issuecomment-71185519

Gemfile

gem 'devise', github: 'plataformatec/devise'