Preventing Heroku from using precompiled assets in development mode

Question

Currently it seems Heroku is determined to pre-compile assets when I push my code up to my instances.

This is great for production servers, however for my "RAILS_ENV=development" server, this causes issues, as I now get pages with all the JavaScript files served up individually from my asset manifest, and then another file with the same code all grouped up as the pre-compiled asset.

This cause my jquery datatables libraries to break, throwing popup errors, which I don't get on my local environment (development or production) or in my production Heroku instance.

Is there anyway to disable pre-compilation of assets on Heroku for development mode instances ? Or is there any reason why these aren't already disabled on development Heroku servers already ?

Answer 1

If Heroku detect a public/assets/manifest.yml file then they will not attempt to precompile your assets and assume you are dealing with them yourself. More details at http://devcenter.heroku.com/articles/rails31_heroku_cedar

Answer 2

AFAIK, Heroku has to precompile assets to work around their readonly FS and the fact that the Rails asset pipeline wants to write files to the FS. The only thing I could suggest would be to work out why your assets are breaking when being compiled.

Answer 3

I worked around this by adding some voodoo to my Rakefile to disable the assets:precompile rake task.

first I add the user-env-compile labs component

heroku labs:enable user-env-compile

then add this to the beginning of my Rakefile

# found from http://blog.jayfields.com/2008/02/rake-task-overwriting.html
# used by conditional heroku asset compile magick
class Rake::Task
  def overwrite(&block)
    @actions.clear
    enhance(&block)
  end
end

Then I add this rake task in lib/tasks/disable_assets_on_heroku.rake

if ENV['RAILS_ENV'] == 'development'
  namespace :assets do
    task(:precompile).overwrite do
      puts "Asset precompile skipped in #{ENV['RAILS_ENV']}"
    end
  end
end