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Haml Coffee Assets compiles Haml Coffee templates in the Rails 3.1 asset pipeline, so you can use them as JavaScript templates in your JavaScript heavy Rails application. Server-side rendering of templates is also possible, allowing you to share the same template files for Rails and JavaScript templates. It also works as a pure Sprockets engine without Rails.

Tested on MRI Ruby 1.9.3, 2.0.0 and the latest version of JRuby.


  • Seamless integration of Haml-Coffee into the Rails asset pipeline or as standalone Sprockets engine.
  • Manifold options to configure Haml Coffee Assets to your needs.
  • AMD support.
  • Server-side rendering of templates in Rails.

Haml Coffee

Haml Coffee allows you to write inline CoffeeScript in your HAML JavaScript templates:

  %h2 Cart
  - if @cart.length is 0
    %p.empty Your cart is empty
  - else
      - for item in @cart
            %a{ :href => "/cart/item/remove/#{ }" } Remove Item

You can try Haml Coffee online by visiting Haml Coffee Online and have a look the AMD example Rails app.


The simplest way to install Haml Coffee Assets is to use Bundler. Add haml_coffee_assets and execjs to your Gemfile:

group :assets do
  gem 'haml_coffee_assets'
  gem 'execjs'

(note that Rails 4.0 removed the assets group from Gemfile and so you don't need that line) and require the hamlcoffee.js in your app/assets/javascripts/templates/

#= require hamlcoffee

If you're using AMD support then you do not need to include the above helper, since it will be automatically included.

This provides the default escaping and the global context functions. Read more about it in the configuration section below.

Please have a look at the CHANGELOG when upgrading to a newer Haml Coffee Assets version.

If you want to use Haml Coffee with Sinatra, please have a look at the Haml Coffee Sinatra demo application.


Haml Coffee Assets allows two different ways of generating your JavaScript templates, but the Haml Coffee template generation is preferred, since it provides more configuration options and a smoother experience.

Haml Coffee template generation

  • Extension: .hamlc

If you omit the .jst and give your templates only a .hamlc extension, then Haml Coffee Assets will handle the JavaScript template generation. With this approach you can easily define your own namespace with a simple configuration and you can use the template name filter.

You can place all your Haml Coffee templates in the app/assets/javascripts/templates directory and include all templates from your app/assets/javascripts/

#= require_tree ./templates

Because Haml Coffee Assets provides a default template name filter, the templates/ prefix will be automatically removed.

Sprocket JST processor template generation

  • Extension: .jst.hamlc

When you give your templates the extension .jst.hamlc, Haml Coffee Assets will only generate the template function, which then in turn will be further processed by the Sprocket JST processor. Because Haml Coffee Assets will not generate the template, you can't use the AMD support, template name filter and the JST namespace definition is more cumbersome compared to the Haml Coffee template generation.

With this approach you should place all your Haml Coffee templates in the app/assets/templates directory and include all templates from your app/assets/javascripts/

#= require_tree ../templates

If you would place your templates into app/assets/javascripts/templates, then all your JST template names would begin with templates/, which may be not what you want.

Server-side rendering in Rails

Haml Coffee Assets registers the .hamlc extension with Action View, so that Rails templates can be written in Haml Coffee. Rails will see templates placed in app/assets/javascripts/templates (though this path can be changed if you store your templates in another directory), and the same template files can be rendered via Rails or via JavaScript on the client. Server-side rendering is only available when using the global placement and not with the AMD placement.

Given a Haml Coffee template at app/assets/javascripts/templates/books/_book.hamlc:

  %dt Name
  %dd= @name
  %dt Author
  %dd= @author

And a Haml Coffee context at app/assets/javascripts/templates/context.js:

//= require hamlcoffee

To render on server in books#index:

= render "book", :name => "A Tale of Two Cities", :author => "Charles Dickens"

To render and render the same file on the client using the asset pipeline:

#= require hamlcoffee
#= require templates/books/_book

JST["books/book"](name: "A Tale of Two Cities", author: "Charles Dickens")

Note that the template is required as books/_book because it refers to the actual file, but the template name on the client is simply books/book. If you require all templates at once with #= require_tree ./templates, you won't need to remember this distinction.


Please note that all configuration examples will use the paths of the Haml Coffee template generation and not the Sprocket JST processor template generation.

Sprockets will cache your templates after compiling and will only recompile them when the content of the template has changed, thus if you change to your configuration, the new settings will not be applied to templates already compiled. You can clear the Sprockets cache with:

rake assets:clean

For Rails, you can set the configuration options in your environment by accessing config.hamlcoffee, whereas if you just use the plain Sprockets engine you can access the configuration with HamlCoffeeAssets.config. All the following examples use the Rails way.

Please note: When you put Haml Coffee Assets into the :assets group within your Gemfile and precompile the assets (the default Rails behaviour), then Haml Coffee Assets is not loaded in production and you can't set any configuration at config.hamlcoffee in both config/application.rb and config/environments/production.rb.

You can simply add a condition around the configuration:

if defined? ::HamlCoffeeAssets
 config.hamlcoffee.awesome = true

or move your configuration to config/environments/development.rb (and config/environments/test.rb, depending on your JavaScript testing setup).

Document format

By default all Haml Coffee templates are rendered to a HTML5 document. You can choose between the following output formats:

  • html5
  • html4
  • xhtml

If you prefer another HTML format than HTML5, you can set it in your config/application.rb:

config.hamlcoffee.format = 'xhtml'

Template placement

By default all Haml Coffee templates are placed under the configured template namespace. You can choose between the following placements:

  • global
  • amd

By setting the placement option to amd, each template will be wrapped within a define function, enabling the usage of a module loader.

config.hamlcoffee.placement = 'amd'

Please note, the placement option is only applicable if you use the .hamlc extension and let Haml Coffee Assets handle the JST generation. The global hamlcoffee helpers must be loaded normally before making use of any templates due to the current template design.

Global template dependencies

Haml Coffee Assets allows you to globally define the module dependencies for all templates. By default, the Haml Coffee Assets helper is included, but you can add your own:

config.hamlcoffee.dependencies = { '_' => 'underscore', :hc => 'hamlcoffee_amd' }

If you do not include the hamlcoffee_amd module as hc in the list, then the helper methods will be included in each template, increasing its size. It's recommended to always have the hamlcoffee module included.

Template namespace

By default all Haml Coffee templates are registered under the JST namespace. A template app/assets/javascripts/templates/header.hamlc with the given content:

  %h2= @title

will be accessible in your browser as JST['header']. You can now render the precompiled template and pass the data to be rendered:

JST['header']({ title: 'Hello Haml Coffee' })

If you prefer another namespace, you can set it in your config/application.rb:

config.hamlcoffee.namespace = 'window.HAML'

You can even set a deep nested namespace like window.templates.HAML and Haml Coffee will handle creation all the way down.

You can't use this configuration if you give your templates a .jst.hamlc extension, because the Sprockets JST processor handles the template generation. In this case you have to subclass the JST processor:

class MyJstProcessor < Sprockets::JstProcessor
  def prepare
    @namespace = 'MyApp.Tpl'

Foo::Application.assets.register_engine '.jst', MyJstProcessor

And you must make sure MyApp exists before any template is loaded.

Template name

The name under which the template can be addressed in the namespace depends not only from the filename, but also on the directory name by default.

The following examples assumes a configured namespace window.JST and the asset template directory app/assets/javascripts/templates:

  • app/assets/javascripts/templates/login.hamlc will become JST['login']
  • app/assets/javascripts/templates/users/new.hamlc will become JST['users/new']
  • app/assets/javascripts/templates/shared/form/address.hamlc will become JST['shared/form/address']

Template name filter

If you wish to put the templates in a different location, you may want to change the name_filter config.

config.hamlcoffee.name_filter = lambda { |n| n.sub /^templates\//, '' }

By default, name_filter strips the leading templates/ directory off of the name and also a leading _ from the template name. Please note, name_filter is only applicable if you use the .hamlc extension and let Haml Coffee Assets handle the JST generation. If you use the .jst.hamlc extension, then Sprockets JST processor will name things accordingly (e.g., with templates/ intact in this case).

The template name filter is not used with AMD loader.


If you don't want to have your directory names under which your template is located to be contained in the JST name, you can configure Haml Coffee in your config/application.rb to strip off the path to the file name and only use the basename as JST name:

config.hamlcoffee.basename = true

With this setting enabled the following naming rule applies:

  • app/assets/javascripts/templates/login.hamlc will become JST['login']
  • app/assets/javascripts/templates/users/new.hamlc will become JST['new']
  • app/assets/javascripts/templates/shared/form/address.hamlc will become JST['address']

This setting has only an effect when you're using Haml Coffee to generate the JST and not when using the Sprockets JST processor.


All generated output by running CoffeeScript in your template is being escaped, but you can disable escaping of either the attributes or the generated Html.

Attribute escaping

You can toggle attribute escaping in your config/application.rb:

config.hamlcoffee.escapeAttributes = false

HTML escaping

You can toggle HTML escaping in your config/application.rb:

config.hamlcoffee.escapeHtml = false

Clean values

Every value that is returned from inline CoffeeScript will be cleaned by default. The included implementation converts null and undefined to an empty string. You can disable value cleaning in your config/application.rb:

config.hamlcoffee.cleanValue = false

Uglify generated HTML

By default all generated HTML is indented to have a nice reading experience. If you like to ignore indention to have a better rendering performance, you can enable the uglify option in your config/application.rb:

config.hamlcoffee.uglify = true

Global context

Haml Coffee Assets allows you to configure a global context function that gets merged into the local template context for each template. You can simply override HAML.globals and return the global context data:

HAML.globals = ->
    isAuthenticated: App.isAuthenticated()
    isAdmin: App.currentUser.hasRole('admin')

Now you can use the properties from the global context in every template:

  %h1 Page not found
  - if @isAuthenticated
    %p Please visit the home page.
  - else
    %p Please log into your account.

When rendering on the server, haml_coffee_assets will expect the global context to be overriden with the global_context_asset. Located by default at templates/context.

You can configure the path to this asset in your config/application.rb:

config.hamlcoffee.global_context_asset = 'templates/context'

If you like to use your own implementation, simply configure your context function in your config/application.rb:

config.hamlcoffee.context = 'App.globalTemplateContext'

or disable the global context completely:

config.hamlcoffee.context = false

Your custom context function must take the local context as parameter and returns the merged context data. The following example uses the Haml Coffee Assets extend function to merge the global context data with the passed local context data:

App.globalTemplateContext = (locals) -> HAML.extend({}, {
    authenticated: App.isAuthenticated()
}, locals)

Please have a look at the wiki for further examples on how to use the global context.

Customize the tag lists

Haml Coffee contains two list of HTML tags that you can customize. In general you're fine with the defaults, but if you need to extend the list, you can instruct Haml Coffee Assets to do so.

Whitespace sensitive tag list

  • Tags: textarea, pre

Some HTML tags are whitespace sensitive, which means that whitespace used for proper indention results in a wrong display of the tag. In order to avoid this, the content is preserved by converting the newlines to a HTML entity. You can set your own list of whitespace sensitive tags in your config/application.rb:

config.hamlcoffee.preserveTags = 'pre,textarea,abbr'

This list is also taken into account for the HAML.preserveAndFind helper function that is provided and its shortcut notation ~.

Auto-closing tag list

Tags: meta, img, link, br, hr, input, area, param, col, base

The auto-closing tag list will contains the tags that will be self-closes if they have no content. You can set the list of self closing tags in your config/application.rb:

config.hamlcoffee.autoclose = 'meta,img,link,br,hr,input,area,param,col,base'

Custom helper functions

Haml Coffee Assets provides a set of custom functions for Haml Coffee, so that the templates doesn't have to be self contained and can make use of the global functions. In general you don't have to customize them further, but if you need to, you can set custom functions for:

  • config.hamlcoffee.customHtmlEscape
  • config.hamlcoffee.customCleanValue
  • config.hamlcoffee.customPreserve
  • config.hamlcoffee.customFindAndPreserve
  • config.hamlcoffee.customSurround
  • config.hamlcoffee.customSucceed
  • config.hamlcoffee.customPrecede

You can see the default implementation and the Haml Coffee documentation for more information about each helper function.

Templates path

Rails will look for templates in app/assets/javascripts/templates when rendering on the server side. If you store your templates in another directory, you can change this location:

config.hamlcoffee.templates_path = "custom/template/path"

Partial rendering

With Haml Coffee Assets you can render partials when using plain JST approach and also with AMD support.

JST partial rendering

With the traditional JST approach, all the templates are globally accessible in your defined namespace, which is JST by default. This allows you to render a template within another template like:

%h1 Comments for this article
- for comment in @article.comments
  != JST['articles/comment'](comment)

AMD partial rendering

Haml Coffee parses the template source code for require statements and adds them to the template module dependencies. This allows you to require other templates like this:

- require 'module'
- require 'deep/nested/other'

Now your dependencies are available in the template, allowing you to render it with:

!= module()
!= other()

Please note that only the basename ot the template is used as module variable name.

Of course you can also directly require and render a template like:

!= require("another/other")()

Please have a look at the AMD example Rails app for a working example.


Developed by Michael Kessler, FlinkFinger.

If you like Haml Coffee Assets, you can watch the repository at GitHub and follow @netzpirat on Twitter for project updates.


Pull requests are very welcome! Please try to follow these simple rules if applicable:

  • Please create a topic branch for every separate change you make.
  • Make sure your patches are well tested. All specs must pass.
  • Update the Yard documentation.
  • Update the README.
  • Update the CHANGELOG for noteworthy changes.
  • Please do not change the version number.

For questions please join #haml on

Open Commit Bit

Guard has an open commit bit policy: Anyone with an accepted pull request gets added as a repository collaborator. Please try to follow these simple rules:

  • Commit directly onto the master branch only for typos, improvements to the readme and documentation (please add [ci skip] to the commit message).
  • Create a feature branch and open a pull-request early for any new features to get feedback.
  • Make sure you adhere to the general pull request rules above.


See the CHANGELOG and the GitHub list of contributors.


  • Jeremy Ashkenas for CoffeeScript, that little language that compiles into JavaScript.
  • The people at 9elements who started haml-coffee, an elegant JavaScript template solution.


(The MIT License)

Copyright (c) 2011-2013 Michael Kessler

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.