Markdown Discuss - Jun 2006 - trailing spaces in code block

It seems that Markdown 1.0.1 strips off trailing spaces at the end of
code blocks.  Is this really what it's supposed to do?  There might be
reasons to include trailing spaces in code displayed on a web page --
for example, in demonstrating how to do a hard line break in markdown.
Even if the trailing spaces aren't visible, they can be cut and 
pasted.  Besides, Markdown 1.0.1 preserves trailing spaces on
every line except the last line of a code block.  Is there a reason
to treat the last line differently?

The reason I ask is that I've written an implementation of markdown in
haskell.  It passes all of the tests in the test suite except "Markdown
Documentation - Syntax.text", which it fails because it retains the
trailing spaces in the code block at line 572.  I could of course change
it to remove trailing spaces in code blocks, but if this is a bug and
not a feature, I'd rather see the test suite changed.  Any thoughts?

John

John MacFarlane <jgm@berkeley.edu> wrote on 6/14/06 at 3:12 PM:
> It seems that Markdown 1.0.1 strips off trailing spaces at the end of
> code blocks.  Is this really what it's supposed to do?  There might be
> reasons to include trailing spaces in code displayed on a web page --
> for example, in demonstrating how to do a hard line break in markdown.
> Even if the trailing spaces aren't visible, they can be cut and 
> pasted.  Besides, Markdown 1.0.1 preserves trailing spaces on
> every line except the last line of a code block.  Is there a reason
> to treat the last line differently?
No, I don't think so. If there is a reason that I implemented it
this way, I have forgotten it, and I can't think of any reason it
should act like this, so I'm calling it a bug in Markdown.pl. (And
in Markdown.php, too, for obvious reasons.)

The fix is easy. Inside _DoCodeBlocks(), change this:

    $codeblock =~ s/\s+\z//; # trim trailing whitespace

to this:

    $codeblock =~ s/\n+\z//; # trim trailing newlines

> The reason I ask is that I've written an implementation of markdown in
> haskell.  It passes all of the tests in the test suite except
"Markdown
> Documentation - Syntax.text", which it fails because it retains the
> trailing spaces in the code block at line 572.  I could of course change
> it to remove trailing spaces in code blocks, but if this is a bug and
> not a feature, I'd rather see the test suite changed.  Any thoughts?
Yup. Just remove the spurious spaces at the end of line 572 in
"Markdown > Documentation - Syntax.text".

I'll also add a test to test this "preserve spaces on the last
line of a code block" fix.

Thanks for reporting this John. When (if?) you release your
Haskell port, be sure to add it to the list of implementations
here:

    http://markdown.infogami.com/
    
-J.G.