Andreas Böhrnsen

Consulting and Development

Using libSass in Middleman

After my long evening trying to upload the last blog post I wanted to make the livereload experience a bit better and tried to integrate libSass into Middleman. Here is how.

Digging into the Middleman gem I found that the ‘main’ gem is just a package of other gems. Running bundle viz I got the following image:

Gem graph (click to enlarge)

The same can be seen in the source code. It only requires middleman-core and includes a bunch of gems in the spec file:

s.add_dependency("middleman-core", Middleman::VERSION)
s.add_dependency("middleman-sprockets", ">= 3.1.2")
s.add_dependency("haml", [">= 4.0.5"])
s.add_dependency("sass", [">= 3.4.0", "< 4.0"])
s.add_dependency("compass-import-once", ["1.0.5"])
s.add_dependency("compass", [">= 1.0.0", "< 2.0.0"])
s.add_dependency("uglifier", ["~> 2.5"])
s.add_dependency("coffee-script", ["~> 2.2"])
s.add_dependency("execjs", ["~> 2.0"])
s.add_dependency("kramdown", ["~> 1.2"])

Most of these gems I do not use. Today I would not write Coffeescript any more but only ES2015, not use Compass but libSass with mixins, not Haml but plain Html (for performance I guess), not use Kramdown but Redcarpet for Markdown parsing.

So I ripped out the stuff that I needed and changed my Gemfile from this:

source 'https://rubygems.org'

gem "middleman", "~> 3.4"

to this:

source 'https://rubygems.org'

gem "middleman-core", "~> 3.4"
gem "middleman-sprockets", ">= 3.1.2"
gem "uglifier", "~> 2.5"
gem "execjs", "~> 2.0"
gem "sass"

(just shown the middleman part)

Much better!

Now adding libSass was just replacing sass with the sassc gem and all seems to work fine!

Final result:

source 'https://rubygems.org'

gem "middleman-core", "~> 3.4"
gem "middleman-sprockets", ">= 3.1.2"
gem "uglifier", "~> 2.5"
gem "execjs", "~> 2.0"
gem "sassc", "~> 1.8" # <- added libSass

Using and running Middleman did not change, just start it with bundle exec middleman.

Hope that helps.

Update 2015-12-03

The interesting thing is that sassc itself imports sass. So, how can we be sure that really sassc is used and not sass?

Sassc is faster than sass (that’s why we are using it, right?). You will notice that especially for large projects. You can also check this programmatically.

If we have sass included in our Gemfile we can compile a Sass string in the context of the bundle like this:

❯ bundle console
>> Sass.compile "body { color: red }"
=> "body {\n  color: red; }\n"

This does not work anymore if we have sassc installed. We need to use the SassC method.

❯ bundle console
>> Sass.compile "body { color: red }"
NoMethodError: undefined method `compile' for Sass:Module

>> SassC::Engine.new("body { color: red; }").render
=> "body {\n  color: red; }\n"

It also seems that sassc just uses sass to import some sass functions as you can see on Github.

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