Markdown Discuss - May 2007 - Markdown generates invalid html for a list immediately followed by a quote

Howdy,

[Please preserve the CC to 424919-forwarded at bugs.debian.org on any
replies.]

The following bug in Markdown was reported to the Debian bug tracking
system.  In short, running both the released version of Markdown and
the latest beta on

 * foo
 > bar
 > baz

produces invalid HTML.

----- Forwarded message from Joey Hess <joeyh at debian.org> -----

From: Joey Hess <joeyh at debian.org>
To: Debian Bug Tracking System <submit at bugs.debian.org>
Subject: Bug#424919: generates invalid html for a list element immediately
followed by a quote
Date: Thu, 17 May 2007 16:07:35 -0400
X-Spam-Status: No, hits=-8.5 required=4.0 tests=BAYES_00,FROMDEVELOPER,
	HAS_PACKAGE,HTML_MESSAGE,RCVD_IN_SORBS autolearn=ham 
	version=2.60-bugs.debian.org_2005_01_02

Package: markdown
Version: 1.0.1-6
Severity: normal

joey at kodama:~>cat foo
* foo
> bar
> baz
joey at kodama:~>markdown foo
<p><ul>
<li>foo</p>

<blockquote>
  <p>bar
  baz</li>
  </ul></p>
</blockquote>

Notice that the closing tags are not in the right order..

If a newline is added before the quote, it closes the list before starting
the blockquote, so that's a workaround.

(This also happens with markdown 1.0.2~b8-1)

-- System Information:
Debian Release: lenny/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: i386 (i686)

Kernel: Linux 2.6.20-1-686 (SMP w/1 CPU core)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages markdown depends on:
ii  perl                          5.8.8-7    Larry Wall's Practical
Extraction

markdown recommends no packages.

-- no debconf information

-- 
see shy jo



----- End forwarded message -----

-- 
Matt

Le 2007-05-22 ? 23:48, Matt Kraai a ?crit :
> * foo
> > bar
> > baz
Although it should certainly be valid HTML, the output Markdown  
should generate for that is a pretty tricky question in my opinion. I  
see three valid interpretations according to the Markdown syntax  
documentation. Here is the simplest:

     <ul>
     <li>foo
     > bar
     > baz</li>
     </ul>

It also happens to be PHP Markdown's output. bar and baz are taken as  
part of the list item since the following lines do not need to be  
indented, and since the list item does not contain any blank line the  
content gets treated as a span-level, hence no blockquote.

The next one is what most people would expect I think:

     <ul>
     <li>foo</li>
     </ul>

     <blockquote>
       <p>bar
       baz</p>
     </blockquote>

Blockquote markers are obeyed and are on the same level as the list  
since they aren't indented.

Third option:

     <ul>
     <li><p>foo</p>

     <blockquote>
       <p>bar
       baz</p>
     </blockquote></li>
     </ul>

Blockquote markers are seen as inside the list item since adjacent  
lines do not need indentation, and are obeyed making the list item  
content's block-level.

I think, as a general rule, the explicit syntax should take  
precedence over the lazy one. This would make the second option above  
the preferred one over the others. Other tricky cases could work like  
the following.

A list item containing a "foo" paragraph and a "bar baz"
blockquote:

     *   foo
         > bar
         > baz

A list item containing a "foo" paragraph and a "bar"
blockquote,
followed by a "baz" blockquote:

     *   foo
         > bar
     > baz

A list item containing a "foo" paragraph, followed by a "bar
baz"
blockquote:

     *   foo
         > bar
     baz

A list item containing "foo" (no paragraph), followed by a blockquote
containing "bar", followed by a list item containing "baz"
(no
paragraph):

     * foo
     > bar
     * baz

Basically, I'd eliminate any "half-lazy" syntax were you can be
lazy
about list item indentation while not being lazy on blockquote  
markers. This just creates confusion; syntax markers shouldn't be  
allowed to be lazy.

Removing half-lazy things would also fix a surprising issue with  
blockquotes:

     > foo
     > > bar
     > baz

This would be seen as a blockquote containing a "foo" paragraph, a  
nested "bar" blockquote and a "baz" paragraph, instead of
the
completly counter-intuitive output produced today. To make "baz" part
of the nested blockquote, you would either go the explicit route:

     > foo
     > > bar
     > > baz

or the lazy route:

     > foo
     > > bar
     baz

but not something in between.


Michel Fortin
michel.fortin at michelf.com
http://www.michelf.com/

Howdy,

The attached patch prevents Markdown from generating invalid HTML if a
list is followed immediately by a quote, e.g.,

* foo
> bar
> baz
-- 
Matt
-------------- next part --------------
diff -Nru /tmp/ZHVRVKY7mc/markdown-1.0.2~b8/Markdown.pl
/tmp/dDW4tYqXOK/markdown-1.0.2~b8/Markdown.pl
--- /tmp/ZHVRVKY7mc/markdown-1.0.2~b8/Markdown.pl	2007-06-12 22:58:14.000000000
-0700
+++ /tmp/dDW4tYqXOK/markdown-1.0.2~b8/Markdown.pl	2007-06-12 22:58:15.000000000
-0700
@@ -858,6 +858,11 @@
 		  (								# $4
 			  \z
 			|
+			  \n
+			  (?=						# Lookahead for a blockquote
+				[ \t]*>
+			  )
+			|
 			  \n{2,}
 			  (?=\S)
 			  (?!						# Negative lookahead for another list item marker