Block comments in html.erb templates in rails

Question

How do you comment out html mixed with ruby code?

some text <% ... %> more text <%= ... %>
something else
<% ... %>

In js

Answer 1

The only acceptable solution I ever found to this back-breaking problem was to put a space within the "<%=" to make it no longer register as ruby code, and then comment out the whole block with html comments

Like this:

<!--
<p>
  < %= @some_object.some_attribute %>
</p>
<p>
  < %= @some_object.another_attribute %>
</p>
<p>
  < %= @some_object.some_attribute %>
</p>
<p>
  < %= @some_object.some_attribute %>
</p>
-->

Yes, adding the spaces is annoying. But it is the least annoying of all the solutions I've yet seen.

Answer 2

The =begin approach is annoying because:

1. It doesn't work for mixed HTML and Ruby (or just HTML) that's on a single line
2. It's annoying to type

The <% if false %> approach works, but it looks weird and doesn't give anyone else who looks at your code a hint about your intentions.

My solution is as follows:

In application_helper.rb, add a method so:

def comment
end

Then in your view template, you can say:

<% comment do %>Some stuff that won't be rendered...<% end %>

This works because any Ruby method can take a block, but will silently ignore the passed-in block if your method doesn't include a yield.

Answer 3

Use a HEREDOC called comment

Pros:

• Self-explanatory that this is a comment
• Works for erb and HTML tags
• Has ok syntax highlighting (as one long string)

Cons:

• Weird 3 line closing syntax
• No keyboard shortcuts

Code:

The opening tag can be

<% <<-COMMENT %>

the above closing erb tag is just for looks (to match the end),
but don't put anything else there, it may show up on the page

or

<%
<<-COMMENT
%>

Anything here won't run or show up in the browser

<P>
    this will not be displayed in the browser
    <strong> even in the developer's tools </strong>
</p>

<% 1_000_000_000_000.times do |count| %>

for the <%= count %>'th time, this won't run a trillion times,
this is all just a string

all of these %>, <%, <% end %>, end, do, <!--, won't cause any issues.

but the below opening erb tag is important (if you used any erb tags in the comment).
I have no clue why?

The closing tag

yes it needs to be 3 lines

Answer 4

<% %w(
  <span title="<%= title %>">hello</span>
) %>

I hope I've just blown your minds!

Answer 5

Sublime Text's block comment shortcut ctrl+shift+/ notices whether you've selected normal HTML or an Erb tag and puts either the <!--- or <% =begin %> accordingly.

Answer 6

For block comments in templates, my text editor (Komodo) finds this variation on @Garfield's recommendation least obnoxious:

<%# A long multiline comment in a rails template ...
  # line 2
  # and so on ... 
  # %>