From: Phrogz <gavin@...>
Date: 2007-01-01T03:05:06+09:00
Subject: Re: ERb Request

matt wrote:
> Well what it looks like is a bit of preference, and it should stick with
> ERb's '<%' tagging convention, so something like '<%*' and '*%>'
>
> It will absolutely need to have mandatory start and end tags that are
> distinguishable from other tags, and be able to ignore all data and
> information within these tags, sending nothing to the browser (or other
> stream)

Here's a simple patch that does this:

[sliver:/usr/local/lib/ruby/1.8] gkistner$ diff -u erb.rb
erb_with_block_comment.rb
--- erb.rb      2006-12-31 10:53:06.000000000 -0700
+++ erb_with_block_comment.rb   2006-12-31 10:54:01.000000000 -0700
@@ -688,7 +688,7 @@
     @safe_level = safe_level
     compiler = ERB::Compiler.new(trim_mode)
     set_eoutvar(compiler, eoutvar)
-    @src = compiler.compile(str)
+    @src = compiler.compile(str.gsub(/<%\*.+?\*%>/m,''))
     @filename = nil
   end

Probably this would be better implemented as part of the scanner for
ERB, but this could be a base test for desired functionality around
edge cases.

> 1. nested block comments should be checked
> <%* <%*  *%> *%>

What do you mean by 'checked'? Allowing nesting, or throw an error?
The simple hack I provided above fails on nested comments.

Is this really important? As far as I know, C++, JavaScript and Ruby
all disallow the nesting of their block comment style. Lua allowed it
in 5.0, but as of 5.1 it requires that the author use unique block
comment delimiters for each nested level.

It's certainly doable...but is the performance cost worth it?

> 2. N start tags and N-1 stop tags
> <%* <%* *%>

I would say that, like other languages, this case should be treated
fine. (You're asking ERB to ignore all things that look like ERB
commands inside the block comment; shouldn't that include ignoring
something that looks like a block comment start?

The hack I have above treats this as a single block comment.

> 3. M start tags and M+1 stop tags
> <%* *%> *%>

The hack I have above treats this case as degenerate, leaving a lone
*%> in the source and causing ERB to barf. This seems consistent with
how many other languages handle block comments.


>   Erb Comment within HTML Comment
>   <!-- <%*  *%> -->

This should emit an HTML comment with no content, correct?


>   Overlapping HTML/ERb comment
>   <!-- <%*  --> *%>

This should emit broken HTML (an unpaired comment start), since ERB has
no knowledge of SGML/HTML/XML.


> By making a block comment for embedded Ruby, there would be a way to
> section out large parts of code quickly, easily, and still maintain
> continuity of work.

I'm a fan of this idea, just want to make it solid and make an attempt
at a good implementation before asking for a patch on ruby-core.