Why is heroku running this code in my routes file that should only be run in development mode?

Question

In my routes.rb file I have this code:

if Rails.env.development?
  mount LetterOpenerWeb::Engine, at: "/letter_opener"
end

Because in dev mode we like to have letter_opener open our emails for us. But when I push to heroku, I get this (below). Why is this? Why doesn't heroku ignore this section in my routes.rb?

thanks for anyone who can help!

Bundle completed (23.08s) Cleaning up the bundler cache. -----> Preparing app for Rails asset pipeline Running: rake assets:precompile rake aborted! NameError: uninitialized constant LetterOpenerWeb /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/config/routes.rb:43:in block in <top (required)>' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/actionpack-4.1.2/lib/action_dispatch/routing/route_set.rb:337:in instance_exec' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/actionpack-4.1.2/lib/action_dispatch/routing/route_set.rb:337:in eval_block' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/actionpack-4.1.2/lib/action_dispatch/routing/route_set.rb:315:in draw' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/config/routes.rb:1:in <top (required)>' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application/routes_reloader.rb:40:inblock in load_paths' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application/routes_reloader.rb:40:in each' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application/routes_reloader.rb:40:inload_paths' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application/routes_reloader.rb:16:in reload!' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application/routes_reloader.rb:26:inblock in updater' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.2/lib/active_support/file_update_checker.rb:75:in call' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.2/lib/active_support/file_update_checker.rb:75:in execute' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application/routes_reloader.rb:27:in updater' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application/routes_reloader.rb:7:in execute_if_updated' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application/finisher.rb:71:in block in <module:Finisher>' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/initializable.rb:30:in instance_exec' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/initializable.rb:30:in run' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/initializable.rb:55:in block in run_initializers' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/initializable.rb:54:in run_initializers' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application.rb:300:in initialize!' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/config/environment.rb:5:in <top (required)>' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application.rb:276:in require_environment!' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/railties-4.1.2/lib/rails/application.rb:379:in block in run_tasks_blocks' /tmp/build_91bf7616fa162d43a8d71e23aeee1e99/vendor/bundle/ruby/2.1.0/gems/sprockets-rails-2.1.3/lib/sprockets/rails/task.rb:55:in block (2 levels) in define' Tasks: TOP => environment (See full trace by running task with --trace) ! ! Precompiling assets failed.

Answer 1

I believe that you have to specify your runtime environment, which in this case you want to be ENV=production (as per the request in your output above that states "require_environment!"). I don't know what command/task you are running that causes this error, but try running with the above environment variable set to 'production.' (I can't remember if you need quotes around the word production or not.)

Answer 2

I had a line in a rake task that forced the task to be run only in development mode. But that line was outside of the scope of the rake task, so it affected the entire application.