Les Hill — Monkey Patch!

So after missing the wisdom¹ of this:

And responding to this:

http://b.lesseverything.com/2008/2/19/haml-doesn-t-like-javascript

I went to bed.

This morning I wrote my first Rails (really Haml) Monkey Patch². This adds some of what Steve wanted: undisturbed inline javascript with variable interpolation. I am not sure what else he wanted as I did not read his blog carefully :)

Throw this into lib/inline_javascript.rb

 1 module Haml
 2   module Filters
 3     class InlineJavascript
 4       HEAD =<<EOH
 5 <script type="text/javascript">
 6 //<![CDATA[
 7 EOH
 8 
 9       FOOT =<<EOF
10 //]]>
11 </script>
12 EOF
13 
14       def initialize(text)
15         @text = HEAD + text + FOOT
16       end
17 
18       def render
19         @text
20       end
21     end
22   end
23 
24   module Precompiler
25     def close_filtered(filter)
26       @flat_spaces = -1
27       filtered = filter.new(@filter_buffer).render
28 
29       if filter == Haml::Filters::Preserve
30         push_silent("_hamlout.buffer << #{filtered.dump} << \"\\n\";")
31       elsif filter == Haml::Filters::InlineJavascript
32         # suppress eval option does not apply to us
33         flush_merged_text
34         js = unescape_interpolation(filtered)
35         @precompiled  << "_hamlout.buffer << #{js};"
36       else
37         push_text(filtered.rstrip.gsub("\n", "\n#{'  ' * @output_tabs}"))
38       end
39 
40       @filter_buffer = nil
41       @template_tabs -= 1
42     end
43   end
44 end

Throw this at the bottom of your environment.rb, taken from here http://groups.google.com/group/haml/msg/2d890cf1ede761ea

1 require 'inline_javascript'
2 
3 Haml::Template.options = {
4   :filters => {
5     'javascript' => Haml::Filters::InlineJavascript
6   }
7 }

And then do this in your Haml file:

1 :javascript
2   function oh_yea() {
3     alert('Hello' + '#{@message}')
4   }
5 %a{ :href =>"javascript:oh_yea()" } Oh Yea!

Update

I decided to make a patch and submit it to the Haml folks directly. This gave me the ‘opportunity’ to get git going.

Nathan Weizenbaum took the time to put in a more comprehensive fix to expose the interpolation functionality to all filters — look for it in an upcoming release.

¹ It’s turtles all the way down.

² You do not want to know what my subconscious originally thought up as the way to do this — that was twisted.