Issues with assets compilation (Sprockets + custom preprocessor)

I'm on a Ruby on Rails project using ReactJS, so almost 100% Javascript (well, coffeescript + jsx).

I've made a very simple preprocessor for sprockets to replace $imagePath("xxx") to the real asset path.

It looks like this:

module JSAssetPathPreprocessor
  @in_processing = {}
  class << self
    def call(input)
      # For some reason we can have an infinite loop here...
      unless @in_processing[input[:filename]]
        @in_processing[input[:filename]] = true
        out = input[:data].gsub(/\$imagePath\(['"](.*?)['"]\)/){ "'#{ActionController::Base.helpers.image_path($1)}'" }
        @in_processing.delete(input[:filename])
        return { data: out }
      else
        return { data: input[:data] }
      end
    end
  end
end

Then I register it in initializers

Sprockets.register_preprocessor('application/javascript', JSAssetPathPreprocessor) 

And tada! It's working !

(coffeescript + reactJS)

# ...
<Image src=$imagePath('banners/blocks/01.jpg') />
# ...

Output:

<img src="/assets/banners/blocks/01-69a091fe87763b439602a274a03fb63e5357deed56802a55d1547cd67091bd18.jpg">

Except once I deploy in production, the path is not the good one:

<img src="/images/banners/blocks/01.jpg">

I'm using capistrano and do rake tmp:cache:clear assets:clobber assets:precompile.

I've no clues about what's wrong, doing all of this in local works well, I checked my generated application.js. But not on my server.

I even tested with RAILS_ENV=production in local... And it works T_T.

The assets are regenerated well in production (eg. if I add console.log("xxx") it will display on next release, so no caching problem) but the path still remain wrong.

Any clues or ideas on where I can check ? I guess my preprocessor sucks but I get hard time finding documentation for this version of sprockets.

Useful gems version.

• rails (= 5.0.0.beta3)
• sprockets (3.6.0)
• browserify + react-rails + sprockets-coffee-react