in jekyll/plugins/markdown_converter.rb [89:97]
def convert_codespan(el, indent)
attr = el.attr.dup
lang = extract_code_language!(attr) || 'text'
result = highlight_code(el.value, lang, :span)
attr['class'] = 'code'
attr['class'] += " highlight language-#{lang}" if lang
format_as_span_html('code', attr, result)
end