Rails not serving compressed SVG files

Question

I’ve been using Google PageSpeed to optimize my Rails 5.0 application, and something odd jumped out with SVGs in particular. I use Rack::Deflate to compress static assets like so...

config/application.rb

config.middleware.use Rack::Deflater

...and yet Google PageSpeed was nevertheless complaining about uncompressed SVGs being served.

I thought this was weird, so I added some code to manually compress SVGs as part of asset precompilation. This works perfectly, and I can go to http://myapp.com/sample_image.svg.gz and indeed I get the compressed image file.

However, Google PageSpeed is still complaining about uncompressed assets being served.

It would appear that, just like how Rails 5.0 wasn’t compressing my SVGs, when I compress them manually, it still won’t serve them.

Is there some kind of configuration I need to adjust here to get the compressed SVG files to be served correctly?

Answer 1

I started a discussion about how to resolve this in a comprehensive way, since this also seems to affect font & json files that sprockets will compress but ActionDispatch::Static won't serve. Anyway, here's a solution via a monkeypatch (put in an initializer):

require 'action_dispatch/middleware/static'

ActionDispatch::FileHandler.class_eval do
  private

    def gzip_file_path(path)
      return false if ['image/png', 'image/jpeg', 'image/gif'].include? content_type(path)
      gzip_path = "#{path}.gz"
      if File.exist?(File.join(@root, ::Rack::Utils.unescape_path(gzip_path)))
        gzip_path
      else
        false
      end
    end
end

Answer 2

This is still true for Rails 6.1. I've made a PR to fix this: https://github.com/rails/rails/pull/42407