Weird bug

ABOUT.markdown

I've inherited a legacy Rails app that runs on Ruby 1.8.6. I want to upgrade to 1.8.7, but I get weird bugs. One of them was a weird CSS glitch. Here's what happens:

Note how input.html.erb renders <div id="ribbon"> and then a partial. If you look at the output, the partial gets rendered in both versions of Ruby, but the <div id="#ribbon"> gets rendered only in 1.8.6. It appears that the culprit is the small fragment containing a ruby comment <% #end top div %>. If I remove it, both work the same.

Is this an ERB issue and why does switching Ruby versions trigger it?

input.html.erb

	<div id="flower"></div>
<% if slider ||= false %>
	<div id="bubbles"></div>
</div> <% #end top div %>
<div id="ribbon">
		<%=	render :partial => 'visualisations/slider', :locals => {
			:slider_data => slider_data ||= nil,
		 	:selected_year => year.to_s, 
			:preload_action => url_for( :action => preload_action, :id => preload_params ||= nil ), 
			:before_change_func => (before_change_func ||= nil),
			:on_change_function => on_change_function, 
			:after_change_func => (after_change_func ||= nil),
			:bubble_element_id => 'bubbles', 
			:draw_bubbles => true
			} 
		%>
</div>
<% end %>

output1.8.6.html

	<div id="flower"></div>

	<div id="bubbles"></div>
</div> <div id="ribbon">

<select id="slider_year" name="slider[year]"><option value="1975">1975</option>

output1.8.7.html

	<div id="flower"></div>

	<div id="bubbles"></div>
</div> 

<select id="slider_year" name="slider[year]"><option value="1975">1975</option>

I've also noticed that and blogged about it here: http://www.valentinmihov.com/2009/07/08/weird_erb_comment_functionalities/

I think that making ruby comments in ERB templates is not a good idea. No clue why is happening though.

ERB is in stdlib, so different versions of Ruby can have different bugs. I'll probably work if you make a newline before you close the ERB block. Remember that ERB is (pretty much) gsubbed into normal ruby, so comments can ruin lines.