uninitialized constant Rails::Command::Actions::APP_PATH (NameError) when trying to start Rails engine server

问题

The full error is

~/.gem/ruby/2.4.0/gems/railties-5.1.5/lib/rails/command/actions.rb:8:in `set_application_directory!': uninitialized constant Rails::Command::Actions::APP_PATH (NameError)

I recently upgrade from Rails 4.x to 5.x.

回答1:

You need to generate (or regenerate) "binstubs" for the dummy application.

cd spec/dummy
bundle exec rails app:update:bin

You should now be able to start the dummy application, from the spec/dummy directory, as such:

bundle exec bin/rails server

The spec/dummy/script directory can also be deleted.

来源：https://stackoverflow.com/questions/49627510/uninitialized-constant-railscommandactionsapp-path-nameerror-when-trying