How to inline css when using the rails asset pipel

Question

Instead of having the page include a style tag with a link where to get the css from, which I could add to my view using rails' stylesheet_link_tag helper method, I want to have the css inline directly inside the page.

This is what I came up with so far:

%style(type="text/css")=File.read(physical_asset_path("email.css"))

But I can't find any rails' helper method which gives me the physical path of an asset - physical_asset_path is just a dummy method invented by me.

Anybody knows how to get the physical path of an asset when using rails 3.2.x?

Is there an easier/ better way to get stylesheets - from css files inside the common rails assets paths - inline?

Use case: most email clients don't access external sources (like css, images) without user confirmation. So to get the emails properly displayed I need to embed the CSS inside the emails' HTML.

Answer 1

Use premailer or premailer-rails3

https://github.com/fphilipe/premailer-rails3 or https://github.com/alexdunae/premailer

Joe's Nerd Party say:

We also used the Premailer gem to automatically inline the linked stylesheet in the email views. Our email layout looks something like:

%html
  %head
    = stylesheet_link_tag 'email'

    %style{:type => "text/css"}
      :sass
        @media all and (max-width: 480px)
          table#container
            width: auto !important
            max-width: 600px !important
         ... and so on for the mobile code

    %body 
      Email body here.
      %table
        Lots of tables.

We include a stylesheet in the HTML. Premailer downloads it, processes it, and inserts the css rules inline in the HTML.

The @media rules need to be inline in the email layout, since Premailer can’t handle those being in a separate css file yet.

We use premailer-rails3 to integrate Premailer into Rails 3. Unfortunately, we found a bunch of bugs in premailer and premailer-rails3. Our forks of the projects are at https://github.com/joevandyk/premailer and https://github.com/joevandyk/premailer-rails3. The forks fix some encoding bugs, remove some weird css processing stuff done by premailer-rails3, allow premailer to not strip out embedded rules in the email layouts, and some other things.

We also found a bug in sass-rails, where you can’t embed image-urls in inline sass code. See https://github.com/rails/sass-rails/issues/71 Premailer-rails3 hooks into ActionMailer when the email actually being delivered, not just generated. When running tests, email is not actually sent, so the premailer-rails3 hooks don’t get ran during tests. I haven’t spent the time to see if it’s possible to get the premailer processing to run during tests, but that would be a nice thing to do.

Also, our forks on premailer-rails3 assume that you want premailer to go out and actually download the linked CSS files. It should be possible to use the Rails 3.1 asset pipeline to get the processed css without downloading it. A very special thanks goes to Jordan Isip who did the super annoying job of making sure the emails look great in all the different clients out there. Writing that CSS/HTML did not look fun.

Update:

Roadie appears to be a better option. Thanks to Seth Bro for pointing it out.

Answer 2

Had the same problem, solved it using @phlegx's answer to a similar issue in Premailer.

For an environment-safe solution you need to use

(Rails.application.assets || ::Sprockets::Railtie.build_environment(Rails.application)).find_asset('email.css').to_s

I've packaged it into a helper in my app:

# app/helpers/application_helper.rb
# Returns the contents of the compiled asset (CSS, JS, etc) or an empty string
def asset_body(name)
   (Rails.application.assets || ::Sprockets::Railtie.build_environment(Rails.application)).find_asset(name).to_s
end

Answer 3

tl;dr (without Roadie):

%style(type="text/css")
  = render template: '../assets/stylesheets/email_responsive.css'

---

For actually applying the CSS as inline styles, I recommend roadie-rails (which is a Rails wrapper for Roadie). It also has other neat features like absolutizing hrefs, srcs etc.

A usage combining both inlined (email.scss) and non-inlined (email_responsive.css) stylesheets, both residing in app/assets/stylesheets:

-# This will be inlined and applied to HTML elements.
-# Note that you need to include this in your asset config, e.g.:
-# Rails.application.config.assets.precompile += %w(... email.css)
-# (You need to list it as `email.css` even if it's actually `email.scss`.)

= stylesheet_link_tag 'email'


-# E.g. for media queries which can't be inlined - yeah, some iOS devices support them.
-# This will not be inlined and will be included as is (thanks to `data-roadie-ignore`).
-# `template:` marks it as a full template rather than a partial and disables `_` prefix.
-# We need to add the extension (`.css`) since it's non-standard for a view.

%style(type="text/css" data-roadie-ignore)
  = render template: '../assets/stylesheets/email_responsive.css'

Answer 4

Rails.application.assets.find_asset('email').to_s will return the compiled asset as a string.

Answer 5

Rails.application.assets['asset.js'] will work only in local environment, as rails asset compilation is disabled in both production and staging environment.

Rails.application.assets_manifest.find_sources('asset.js').first.to_s.html_safe should be used to inline css when using rails asset pipeline.

Answer 6

You can use this:

Rails.root.join('public', ActionController::Base.helpers.asset_path("email.css")[1..-1]).read.html_safe