Question: How to work with remote asset?

[PikachuEXE]

I got something like //assets.my.domain/assets/mailer-4d19915455ba1fec1f18ca31aaccf9ce.css
I got this generated URL with this code: = stylesheet_link_tag('mailer.css')

I have no idea how to get local assets

[Mange]

Have you set an asset_host? That is most likely the "problem".

You should be able to create an asset provider that recognizes your asset
host and strips it from the path and then finds it on the file system. This
is most likely the way I'll solve this bug officially.
Den 3 jul 2014 04:38 skrev "PikachuEXE" notifications@github.com:

I got something like
//assets.my.domain/assets/mailer-4d19915455ba1fec1f18ca31aaccf9ce.css
I got this generated URL with this code: =
stylesheet_link_tag('mailer.css')

I have no idea how to get local assets

—
Reply to this email directly or view it on GitHub
#10.

[PikachuEXE]

production.rb:

asset_host = ENV["ASSET_HOST"]
  if asset_host.present?
    config.action_controller.asset_host = if asset_host =~ /%d/
      proc do |source|
        # has to call ENV["ASSET_HOST"] since `asset_host` here is not accessible on execution
        "//#{ENV["ASSET_HOST"] % (Zlib.crc32(source) % 4)}"
      end
    else
      "//#{asset_host}"
    end
    config.action_mailer.asset_host = config.action_controller.asset_host
  end

[bcackerman]

+1

[Mange]

I'll look into it.

[Mange]

You should be able to turn off asset_host in your specific mailer as a workaround:

class MyMailer < ActionMailer::Base
  self.asset_host = nil
end

This will not use the asset host for your images, so it's not a full "solution" to the problem.

[Mange]

Planning for the fix happens in #11. It's not trivial to support this, so be prepared to use a workaround for some time.

[adamwaite]

I have managed to maintain use of the asset_host setting for images (can still use image_tag) and made Roadie use a relative path for the styles by explicitly defining the stylesheet path as relative rather than using the stylesheet_link_tag helper. I had to use a non-digest version of the stylesheet.

[Mange]

Here's another workaround:

class MyMailer < ActionMailer::Base
  include Roadie::Rails::Automatic

  protected
  def roadie_options
    super.combine({
      before_transformation: method(:reverse_asset_host_on_stylesheets)
    })
  end

  def reverse_asset_host_on_stylesheets(dom)
    dom.all_css("link[rel=stylesheet]").each do |link_tag|
      if link_tag["href"]
        link_tag["href"] = link_tag["href"].sub(%r{^https?://assets\d\.mycoolapp\.com}, "")
      end
    end
  end
end

Does that make sense? At least you get asset_host applied to all your images while still having styles inlined. If this works out (or at least a variation of it), I might make this a first-class thing within AssetProviders; a callable you set to reverse the asset_host where possible.

[milgner]

Just came across this and found that while it works in principle, one also has to filter out the digest from the asset path.
My code now looks like this:

  def reverse_asset_host_on_stylesheets(dom)
    unless Rails.application.config.action_mailer.asset_host.nil?
      dom.search('link[rel=stylesheet]').each do |link_tag|
        if link_tag['href']
          pipeline_path = link_tag['href'][Rails.application.config.action_mailer.asset_host.length..-1]
          pipeline_path.sub!(/-[0-9a-f]{32,}(\.\w{1,4})(?:\?.*)\Z?/, '\1')
          link_tag['href'] = '/' + pipeline_path
        end
      end
    end
  end

Edited to fix regex.

[Mange]

Thank you for the heads-up, Marcus! 👍

For other people: Note that his code does not work if the asset host is configured with a block, or an array. Only a single string is supported by the above code. It is also important to remember what happens if you use a %s placeholder in the configured asset host: it will be replaced with a single character (1..4, I think) in the rendered markup, thereby reducing the length by one. In practice, this just means that an extra / might get stripped, but it's still useful to know about it.
Make sure to write tests! :-)