ExecJS coffee script not showing line numbers for compile errors (Rails asset pipeline)

Question

In one of my Rails apps, ExecJS is not showing line numbers for coffeescript compilation errors. My compile error message will look like this:

ExecJS::RuntimeErr         


        

Answer 1

I figured it out -- it's due to the coffee-script-source gem version. In the app that was giving line numbers, bundle show gives coffee-script-source of 1.4.0, whereas the other app had a coffee-script-source version of 1.6.1.

I didn't notice this because the coffee-rails gem doesn't tightly specify this dependency (in both my Gemfiles, I was using gem 'coffee-rails', '3.2'). To get around this, just explicitly specify the coffee-script-source gem version:

gem 'coffee-rails', '3.2.2'
gem 'coffee-script-source', '1.5.0'

and bundle update coffee-script-source.

Hopefully this helps anyone else who might run into this discrepancy.

Answer 2

This can also be fixed with this patch that embeds the line information in the error message for the ruby-coffee-script gem.

If you're using source maps, this patch fixes the coffee-rails-source-maps gem.