How to get code line numbers inside page margins?

I'm using pandoc to generate PDFs from markdown files, when i write a code block with line numbers using {.lang .numberLines} the line numbers goes outside page margins like that:

Code line numbers outside page margins

Is there anyway to fix that.

I tried searching for this issue but most of the answers like this one were for how to fix that behavior when writing pure latex not pandoc flavored markdown.

Solution

Pandoc uses LaTeX and the fancyvrb package to render highlighted code blocks. We can customize the output by configuring the Highlighting environment used by pandoc. That's possible by placing a raw LaTeX snippet at the start of the document (or anywhere, as long as it comes before the first code block).

\DefineVerbatimEnvironment{Highlighting}{Verbatim}{%
  xleftmargin=18pt,commandchars=\\\{\}}

You'll probably have to experiment a bit and should adjust the value of xleftmargin to your liking. See the package documentation of fancyvrb for more customization options.