No source maps generated

[sudoremo]

Problem

According to the documentation, you can enable the generation of inline source maps using the following configuration:

Rails.application.config.sass.inline_source_maps = true

In our case though, this does not generate any source maps in the generated application.css, even after removing tmp/cache entirely. This is in development mode.

Diagnosis

In SassC::Rails::Template#config_options, I have verified that inline_source_maps is indeed enabled, which in turn sets the following options:

opts.merge!(source_map: true,
            source_map_file: '.',
            source_map_embed: true,
            source_map_contents: true)

Looking at the API of sass-embedded, I can't find the aforementioned options though. There are the options source_map and source_map_include_sources instead. Though enabling these does not produce a source map either.

Environment

• rails (7.1.3)
• sprockets (3.7.2)
• sprockets-rails (3.2.2)
• dartsass-sprockets (3.1.0)
• sassc-embedded (1.70.0)

---

Many thanks for your wonderful Gem and for having a look at our issue 👍

[JosephTico]

Same issue

[keithslater]

Same problem here

[Mr0grog]

I’m having the same issue.

Looking at the API of sass-embedded, I can't find the aforementioned options though. There are the options source_map and source_map_include_sources instead. Though enabling these does not produce a source map either.

I can at least explain this: the code here calls sassc-embedded (and then that calls sass-embedded). sassc-embedded takes the options used here (it’s emulating the API of sassc-ruby) and transforms them into the two options you are looking for when it passes things along to sass-embedded: https://github.com/sass-contrib/sassc-embedded-shim-ruby/blob/68900334f3298c2d059be690088824c550fc072e/lib/sassc/embedded.rb#L26-L27

---

Looking at what's happening under the hood in my install (sprockets 4.2.1, sprockets-rails 3.5.2, dartsass-sprockets 3.1.0, sassc-embedded 1.79.0), dartsass-sprockets is getting back a CSS string with a source map in it, so probably something higher up in sprockets or sprockets-rails is stripping out the comment when handling the result.

[Mr0grog]

I figured this out for my case, and it didn’t have anything to do with this gem. Other people might be having issues for a different reason.

For me, the problem was that the app I’m working on used Bootstrap, and the Bootstrap gem pulls in the autoprefixer-rails gem. Even though autoprefixer-rails supports inline source maps when using it manually, it strips them out when using the Sprockets integration (and it autoregisters itself with Sprockets).

If you’ve got autoprefixer-rails installed and still need inline source maps, you can remove it from Sprockets (unfortunately this means no autoprefixing 🤷). You can add this in an initializer or in development.rb:

Rails.application.config.assets.configure do |env|
  AutoprefixerRails.uninstall(env)
end

Alternatively, if you want to keep autoprefixer around…

You can replace the built-in integration with one that supports inline source maps, but it’s a bit more complicated. This worked for me, but I haven’t tested extensively:

# config/initializers/autoprefixer.rb

class AutoprefixerWithSourcemap < AutoprefixerRails::Sprockets
  def self.run(filename, css)
    output = "#{filename.chomp(File.extname(filename))}.css"

    # If you want this nice an generic, you could check `css` for the presence
    # of an inline source map, and set the `map` argument based on that
    # instead of always setting it to `true`.
    result = @processor.process(css, from: filename, to: output, map: true)

    result.warnings.each do |warning|
      warn "autoprefixer: #{warning}"
    end

    result.css
  end

  def self.use_bundle_processor?
    ::Sprockets::VERSION.to_f >= 4
  end

  def self.install(env)
    if use_bundle_processor?
      env.register_bundle_processor("text/css", self)
    else
      env.register_postprocessor("text/css", self)
    end
  end

  def self.uninstall(env)
    if use_bundle_processor?
      env.unregister_bundle_processor("text/css", self)
    else
      env.unregister_postprocessor("text/css", self)
    end
  end
end

Rails.application.config.assets.configure do |env|
  AutoprefixerRails.uninstall(env)
  AutoprefixerWithSourcemap.register_processor(AutoprefixerRails.processor({}))
  AutoprefixerWithSourcemap.install(env)
end

I’ve also filed an issue on autoprefixer-rails if you want to follow that: ai/autoprefixer-rails#228

[JosephTico]

Oh wow you were spot on with that one, @Mr0grog im pretty sure that was also my situation, thank you very much