undefined method `mechanism=' for ActiveSupport::Dependencies:Module (NoMethodError)

Question

I have a problem while generating a controller in rails 7.0.0

When I run the command

rails g controller Home index

It gives me the following error.

/home/dev/.rvm/gems/ruby-3.0.2/gems/spring-2.1.1/lib/spring/application.rb:103:in `block in preload': undefined method `mechanism=' for ActiveSupport::Dependencies:Module (NoMethodError)
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/railties-7.0.1/lib/rails/initializable.rb:32:in `instance_exec'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/railties-7.0.1/lib/rails/initializable.rb:32:in `run'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/railties-7.0.1/lib/rails/initializable.rb:61:in `block in run_initializers'
    from /home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/tsort.rb:228:in `block in tsort_each'
    from /home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
    from /home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/tsort.rb:431:in `each_strongly_connected_component_from'
    from /home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/tsort.rb:349:in `block in each_strongly_connected_component'
    from /home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/tsort.rb:347:in `each'
    from /home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/tsort.rb:347:in `call'
    from /home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/tsort.rb:347:in `each_strongly_connected_component'
    from /home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/tsort.rb:226:in `tsort_each'
    from /home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/tsort.rb:205:in `tsort_each'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/railties-7.0.1/lib/rails/initializable.rb:60:in `run_initializers'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/railties-7.0.1/lib/rails/application.rb:372:in `initialize!'
    from /home/dev/project/spousal/config/environment.rb:5:in `<main>'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/bootsnap-1.10.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/bootsnap-1.10.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/zeitwerk-2.5.3/lib/zeitwerk/kernel.rb:35:in `require'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/spring-2.1.1/lib/spring/application.rb:106:in `preload'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/spring-2.1.1/lib/spring/application.rb:157:in `serve'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/spring-2.1.1/lib/spring/application.rb:145:in `block in run'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/spring-2.1.1/lib/spring/application.rb:139:in `loop'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/spring-2.1.1/lib/spring/application.rb:139:in `run'
    from /home/dev/.rvm/gems/ruby-3.0.2/gems/spring-2.1.1/lib/spring/application/boot.rb:19:in `<top (required)>'
    from <internal:/home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
    from <internal:/home/dev/.rvm/rubies/ruby-3.0.2/lib/ruby/3.0.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
    from -e:1:in `<main>

I have googled but found no solution. So what's the reason for this error?

Answer 1

I recently upgraded an to Rails 7.0.1 and I ran into this same issue. I saw this same error when trying to run rails console.

I got past it when I removed spring-watcher-listen from the Gemfile (because it was preventing spring from updating past 2.x) and then bumped spring to 3.0.0 in the Gemfile. Then I ran bundle and rails console worked again.

This seems like a bump we have to overcome in upgrading Rails as noted in this article under "6. Notable Changes".

Answer 2

same here, on rails g migration ... after updating to rails-7.0.4. allthough i had in my gemfile gem "spring" and ran bundle update, spring ran on 2.x.. changed it in Gemfile to gem 'spring', '~> 4.1' ran bundle and it works.