pandocDelimitedCodeBlock should not requires preceeding or leading empty line

[soraxas]

Hi!

Is there a reason why the code block conceal requires an empty line before and after the three backticks at line 439 and 441?

vim-pandoc-syntax/syntax/pandoc.vim

Line 439 in 0d1129e

call s:WithConceal('codeblock_start', 'syn match pandocDelimitedCodeBlockStart /\(\_^\n\_^\(>\s\)\?\([ ]\{4,}\|\t\)\=\)\@<=\(\~\{3,}\~*\|`\{3,}`*\)/ contained containedin=pandocDelimitedCodeBlock nextgroup=pandocDelimitedCodeBlockLanguage', 'conceal cchar='.s:cchars['codelang'])

The pandocDelimitedCodeBlockStart regex requires two preceding ^ (line 439) and pandocDelimitedCodeBlockEnd requires two leading $ (line 441) which means it needs a blank line before and after.

But as far as I can tell, in markdown the three backticks that begins a block of code can be followed right after text, and the same goes for the ending of code block (can be followed by non-empty lines). They should be valid syntax.

See the following:

Without enabling syntax

Current behaviour

After I edited the code, made it only requires one preceding ^ and leading $ for the begin/end of code regex.

I would expect the third scenario for concealing. Note that highlighting works as expected (as seen by the illustrations), it's only the conceal that doesn't work.