Secrets of the asset pipeline

Secrets Of The
Asset Pipeline
Ken Collins
metaskills.net

Sunday, December 18, 11

The Foundation
What makes the asset
pipeline possible.


Hike


Hike
Hike is a Ruby library for
nding les in a set of paths.
Use it to implement search
paths, load paths, and the like.


Find Ruby Files In Your Project

trail = Hike::Trail.new "/Users/sam/Projects/hike"
trail.append_extension ".rb"
trail.append_paths "lib", "test"

trail.find "hike/trail"
# => "/Users/sam/Projects/hike/lib/hike/trail.rb"

trail.find "test_trail"
# => "/Users/sam/Projects/hike/test/test_trail.rb"


Explore Your Shell Path

trail = Hike::Trail.new "/"
trail.append_paths *ENV["PATH"].split(":")

trail.find "ls"
# => "/bin/ls"

trail.find "gem"
# => "/Users/sam/.rvm/rubies/ree/bin/gem"


Digging Deeper
# Fallback logical paths. Equivalent.
trail.find "hike", "hike/index"
trail.find("hike") || trail.find("hike/index")

# Block yields multiple matches.
trail.find("application") do |path|
return path if mime_type_for(path) == "text/css"
end

# Like Dir#entries. Filters "." and "~" swap files.
trail.entries('/usr/local/bin')

# Like File.stat.
trail.stat('/usr/local/bin')

# Cached trail. Avoids excess system calls.
trail.index


Tilt


Tilt
Tilt is a thin interface over a bunch of
diﬀerent Ruby template engines in an attempt
to make their usage as generic possible. is is
useful for web frameworks, static site
generators, and other systems that support
multiple template engines but don't want to
code for each of them individually.


Common Features


Common Features
Custom template evaluation scopes / bindings.


Common Features
Ability to pass locals to template evaluation.


Common Features
Support for passing a block to template eval for "yield".


Common Features
Backtraces with correct filenames and line numbers.


Common Features
Template file caching and reloading.


Common Features
Template file caching and reloading.
Fast, method-based template source compilation.


Engine File Extension Required Lib.
ERB .erb, .rhtml none (stdlib)
Interpolated String .str none (core)
Erubis .erb, .rhtml, .erubis erubis
Haml .haml haml
Sass .sass sass (>= 3.1)
Scss .scss sass (>= 3.1)
Less CSS .less less
Builder .builder builder
Liquid .liquid liquid
RDiscount .markdown, .mkd, .md rdiscount
Redcarpet .markdown, .mkd, .md redcarpet
BlueCloth .markdown, .mkd, .md bluecloth
Kramdown .markdown, .mkd, .md kramdown
Maruku .markdown, .mkd, .md maruku
RedCloth .textile redcloth

Builder .builder builder
Liquid .liquid liquid
RDiscount .markdown, .mkd, .md rdiscount
Redcarpet .markdown, .mkd, .md redcarpet
BlueCloth .markdown, .mkd, .md bluecloth
Kramdown .markdown, .mkd, .md kramdown
Maruku .markdown, .mkd, .md maruku
RedCloth .textile redcloth
RDoc .rdoc rdoc
Radius .radius radius
Markaby .mab markaby
Nokogiri .nokogiri nokogiri
CoffeeScript .coffee coffee-script (+javascript)
Creole (Wiki markup) .wiki, .creole creole
WikiCloth (Wiki markup) .wiki, .mediawiki, .mw wikicloth
Yajl .yajl yajl-ruby


Really Simple!

require 'erb'
require 'tilt'

template = Tilt.new('templates/foo.erb')
#<Tilt::ERBTemplate @file="templates/foo.rb"...>

template.render # => "Hello world!"


Evaluation Scope

template = Tilt::ERBTemplate.new('templates/foo.erb')
joe = Person.find('joe')
output = template.render(joe, :x => 35, :y => 42)

jane = Person.find('jane')
output = template.render(jane, :x => 22, :y => nil)


Sprockets


Sprockets
Rack-based asset packaging for compiling
and serving web assets. It features
declarative dependency management for
JavaScript and CSS assets, as well as a
powerful preprocessor pipeline that allows
you to write assets in languages like
CoﬀeeScript, Sass, SCSS and LESS.


Rack Application
# In config.ru

require 'sprockets'

map '/assets' do
environment = Sprockets::Environment.new
environment.append_path 'app/assets/javascripts'
environment.append_path 'app/assets/stylesheets'
run environment
end

map '/' do
run YourRackApp
end


Renders Templates
modal.css.scss.erb

/* Multi-line comment blocks (CSS, SCSS, JavaScript)
*= require foo
*/

// Single-line comment blocks (SCSS, JavaScript)
//= require foo

# Single-line comment blocks (CoffeeScript)
#= require foo


Best Practices
How to wire
it up right!


Dir. Structure $ tree app/assets
|
!"" images
#   !"" app
#   #   !"" ...
#   $"" site
#   $"" ...
!"" javascripts
#   !"" application.js
#   | $"" ...
#   !"" shared
#   #   !"" base.js.coffee
#   #   !"" modal.js.coffee.erb
#   #   $"" ...
#   !"" site
| | !"" base.js.coffee
#   | !"" flash.js.coffee
#   | $"" ...
| $"" site.js
$"" stylesheets
!"" application
#   $"" application.css.scss
!"" application.css
!"" shared
#   !"" base.scss
#   !"" modal.css.scss
#   $"" ...
!"" site
#   !"" 960.css
#   $"" site.css.scss
$"" site.css


|
!"" images
#   !"" app

Directory Namespaces #   #   !"" ...
#   $"" site
#   $"" ...
!"" javascripts
#   !"" application.js
#   | $"" ...
#   !"" shared
#   #   $"" ...
#   !"" site
#   | $"" ...
| $"" site.js
$"" stylesheets
!"" application
!"" application.css
!"" shared
#   !"" base.scss
#   $"" ...
!"" site
#   !"" 960.css
#   $"" site.css.scss
$"" site.css


|
!"" images
#   !"" app

#   $"" site
#   $"" ...
!"" javascripts
Manifest Only Top Files #   !"" application.js
#   | $"" ...
#   !"" shared
#   #   $"" ...
#   !"" site
#   | $"" ...
| $"" site.js
$"" stylesheets
!"" application
!"" application.css
!"" shared
#   !"" base.scss
#   $"" ...
!"" site
#   !"" 960.css
#   $"" site.css.scss
$"" site.css


|
!"" images
#   !"" app

#   $"" site
#   $"" ...
!"" javascripts
#   | $"" ...
#   !"" shared

Generators Garbage #   #   !"" base.js.coffee
#   #   $"" ...
#   !"" site
#   | $"" ...
| $"" site.js
$"" stylesheets
!"" application
!"" application.css
!"" shared
#   !"" base.scss
#   $"" ...
!"" site
#   !"" 960.css
#   $"" site.css.scss
$"" site.css


|
!"" images
#   !"" app

#   $"" site
#   $"" ...
!"" javascripts
#   | $"" ...
#   !"" shared

#   #   $"" ...
#   !"" site
Require Tree Bad | |
#   |
!"" base.js.coffee
!"" flash.js.coffee
#   | $"" ...
| $"" site.js
$"" stylesheets
!"" application
!"" application.css
!"" shared
#   !"" base.scss
#   $"" ...
!"" site
#   !"" 960.css
#   $"" site.css.scss
$"" site.css


|
!"" images
#   !"" app

#   $"" site
#   $"" ...
!"" javascripts
#   | $"" ...
#   !"" shared

#   #   $"" ...
#   !"" site
#   |
!"" base.js.coffee
!"" flash.js.coffee
#   | $"" ...
$"" site.js
Try To Match With |
$"" stylesheets
!"" application
Layout Names #   $"" application.css.scss
!"" application.css
!"" shared
#   !"" base.scss
#   $"" ...
!"" site
#   !"" 960.css
#   $"" site.css.scss
$"" site.css


site.js

//= require jquery-1.6.2.min
//= require jquery-ui-1.8.12.ui-darkness.min
//= require jquery_ujs
//= require shared/base
//= require shared/utils
//= require shared/modal
//= require shared/spinner
//= require site/quickie
//= require site/flash
//= require site/site


site.css

/*
*= require application/application
*= require shared/modal
*= require shared/utility
*/


Precompile Additional Assets!
config/production.rb

# Precompile additional assets
# (application.js, application.css,
# and all non-JS/CSS are already added)
config.assets.precompile += ['site.js', 'site.css']


|
!"" images
#   !"" app

#   $"" site
#   $"" ...
!"" javascripts
#   | $"" ...
#   !"" shared

#   #   $"" ...
#   !"" site
#   |
!"" base.js.coffee
!"" flash.js.coffee
#   | $"" ...
$"" site.js
Try To Match With |
$"" stylesheets
!"" application
!"" application.css
!"" shared

Sub Files @import’ed #   !"" base.scss
#   $"" ...
!"" site
#   !"" 960.css
#   $"" site.css.scss
$"" site.css


|
!"" images
#   !"" app

#   $"" site
#   $"" ...
!"" javascripts
#   | $"" ...
#   !"" shared

#   #   $"" ...
#   !"" site
#   |
!"" base.js.coffee
!"" flash.js.coffee
#   | $"" ...
$"" site.js
Try To Match With |
$"" stylesheets
!"" application
!"" application.css
!"" shared

Sub Files @import’ed #   !"" base.scss
#   $"" ...
!"" site
Base Files Are #   !"" 960.css
#   $"" site.css.scss
Your Compass $"" site.css


Base Files Are Your Compass
app/assets/stylesheets/shared/base.scss

$legacy-support-for-ie: false;
$experimental-support-for-opera: false;
$experimental-support-for-khtml: false;
@import "compass";
@import "compass/layout";

app/assets/stylesheets/shared/modal.scss

/*
*= depend_on shared/base.scss
*/
@import "shared/base";


Advanced Usage
Secrets of the
asset pipeline.


Hooking Into Sprockets
Rails.application.assets
# => #<Sprockets::Environment:0x3fda9a195f8c root="/Repos/
homemarks_app", paths=["/Repos/homemarks_app/app/assets/images",
"/Repos/homemarks_app/app/assets/javascripts", "/Repos/
homemarks_app/app/assets/stylesheets", "/Repos/homemarks_app/
vendor/assets/javascripts", "/Repos/homemarks_app/vendor/assets/
stylesheets", "/Users/ken/.rbenv/versions/1.9.3/lib/ruby/gems/
1.9.1/gems/jquery-rails-1.0.13/vendor/assets/javascripts"],
digest="46dde6621c301f4928e3b34efee9e3b5">

Or use the `asset_environment` helper.


Finding Assets
#find_asset method (aliased as [])

Rails.application.assets['shared/modal']
# => #<Sprockets::BundledAsset:0x3fcd7e90c6cc pathname="/
Repos/homemarks_app/app/assets/javascripts/shared/
modal.js.coffee.erb", mtime=2011-11-25 17:41:11 -0500,
digest="775822db3e101bf38d7978627380e62b">


Incomplete
* Advanced Usage
- Where is sprockets.
> Rails.application.assets (helpers can use asset_environment)
- Finding Assets.
#find_asset method (aliased as [])

Notes
Rails.application.assets['shared/modal'] # => Sprockets::BundledAsset
Call to_s on the resulting asset to access its contents, length to get its length in bytes, mtime to
query its last-modified time, and pathname to get its full path on the filesystem.
- Asset Helpers. - image, asset-data-uri, etc.
Move all images to app/assets!!!
Rails.application.assets['site/hmlogo.png']
# => #<Sprockets::StaticAsset:0x3fda99465d08 pathname="/Users/kencollins/Repositories/
homemarks_app/app/assets/images/site/hmlogo.png", mtime=2011-11-16 19:31:44 -0500,
digest="eed9e6f3fd9fa546ccd7ce49edd99f49">
- Custom SASS
- Preprocessors.
- Assets in other assets.
- Precompiling. Fingerprints. When they are used.
- JavaScript Templating with EJS and Eco (read sprockets page)
- JST (define)
- EJS or Eco
- CSS Compressors (:uglifier default, but use :yui for both css/js)
group :assets do
# ...
gem 'yui-compressor', :require => 'yui/compressor'
end
- Your config/application.rb
if defined?(Bundler)
# If you precompile assets before deploying to production, use this line
Bundler.require *Rails.groups(:assets => %w(development test))
# If you want your assets lazily compiled in production, use this line
# Bundler.require(:default, :assets, Rails.env)
end

* CSS Frameworks.
- Less
- Stylus
- Sass
- http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#each-directive
- http://github.com/kuroir/SCSS.tmbundle
- Compass
- mate "$(bundle show compass)/frameworks/compass/stylesheets"


Thanks!
Ken Collins
metaskills.net


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