Coffeescript compilation error in ruby on rails

Question

I am using coffeescript+ruby-on-rails. The compilation of coffeescript into pure JS leads to an error if there is a syntax problem in the coffee code. On the browser when I run the app, I get this error: ExecJS::RuntimeError

Is there any way to find out what caused the compilation error, when it was trying to compile coffee code to JS? Attached is a screenshot of the error

Following is the entry in the server log, which no way indicates the file which actually caused the syntax error:

ActionView::Template::Error (SyntaxError: [stdin]:25:10: unexpected :):
    4:     <meta name="viewport" content="width=device-width, initial-scale=1.0">
    5:     <title><%= content_for?(:title) ? yield(:title) : "Inmonarch Website" %></title>
    6:     <meta name="description" content="<%= content_for?(:description) ? yield(:description) : "Inmonarch Website" %>">
    7:     <%= stylesheet_link_tag 'application', media: 'all' %>
    8:     <%= javascript_include_tag 'application' %>
    9:     <%= csrf_meta_tags %>
   10:   </head>
  app/views/layouts/dashboard.html.erb:7:in `_app_views_layouts_dashboard_html_erb__3120053487817944018_56303120'


  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/actionpack-4.2.6/lib/action_dispatch/middleware/templates/rescues/_source.erb (7.4ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/actionpack-4.2.6/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (3.0ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/actionpack-4.2.6/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (1.6ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/actionpack-4.2.6/lib/action_dispatch/middleware/templates/rescues/template_error.html.erb within rescues/layout (25.5ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/web-console-2.3.0/lib/web_console/templates/_markup.html.erb (0.3ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/web-console-2.3.0/lib/web_console/templates/_inner_console_markup.html.erb within layouts/inlined_string (0.3ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/web-console-2.3.0/lib/web_console/templates/_prompt_box_markup.html.erb within layouts/inlined_string (0.3ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/web-console-2.3.0/lib/web_console/templates/style.css.erb within layouts/inlined_string (0.3ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/web-console-2.3.0/lib/web_console/templates/console.js.erb within layouts/javascript (296.8ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/web-console-2.3.0/lib/web_console/templates/main.js.erb within layouts/javascript (0.2ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/web-console-2.3.0/lib/web_console/templates/error_page.js.erb within layouts/javascript (0.3ms)
  Rendered /home/vipin8169/.rvm/gems/ruby-2.2.3@rails426/gems/web-console-2.3.0/lib/web_console/templates/index.html.erb (313.8ms)

PS:- I know what the syntax error is, I made the syntax error deliberately to find out if I am able to trace the error with the help of logs, which I couldn't.

Answer 1

One workaround is to compile your .coffee files outside rails to get a decent error message:

If you don't yet have it:

npm i coffee-script -g

Then in a parent directory of your .coffee files:

coffee --output deleteme --compile .

When you're done, delete the deleteme folder it created (which is only created if you fix all the errors). This should find the syntax error for you and tell you exactly where it is.