Upgraded ruby from 1.9.3 to 2.1.6, active_admin throws NoMethodError (active_admin.css.scss)

Question

After upgrading my app from ruby 1.9.3 to 2.1.6, accessing my Active Admin-powered admin interface threw the following error:

NoMethodError - undefined method 'empty?' for nil:NilClass (in /Users/myusername/Rails/myapp/app/assets/stylesheets/active_admin.css.scss)

I replicated this error when simply accessing an Active Admin page, and when doing a rake assets:precompile (which happens during a deploy as well).

I tried completely commenting out the contents of active_admin.css.scss , to no avail. My relevant gem versions:

• activeadmin (0.5.1)
• sass (3.4.13)
• sass-rails (3.2.6)
• bootstrap-sass (2.1.1.0)
• rails (3.2.21)

What happened between ruby 1.9.3 and 2.1.6 that might be causing this error with stylesheets?

Answer 1

According to this thread , sass gem 3.1.18 is the first SASS gem release with ruby-2.x compatibility. This led me down the path of upgrading my sass-rails gem from 3.2.4 to 3.2.6, which as a dependency upgraded my sass gem to 3.4.13 (was 3.1.15).

And that did it! No more obscure errors related to active_admin.css.scss or css in general.

UPDATE

sass-rails didn't really need to be updated. Just the sass gem solves the problem (also, upgrading sass-rails inexplicably broke some javascript in the app, specifically it triggered the error History.js Core has already been loaded... found in jquery.history.js).