showdown/src/subParsers/githubCodeBlocks.js

/**
 * Handle github codeblocks prior to running HashHTML so that
 * HTML contained within the codeblock gets escaped properly
 * Example:
 * ```ruby
 *     def hello_world(x)
 *       puts "Hello, #{x}"
 *     end
 * ```
 */
showdown.subParser('githubCodeBlocks', function (text, options, globals) {
  'use strict';

  // early exit if option is not enabled
  if (!options.ghCodeBlocks) {
    return text;
  }

  text = globals.converter._dispatch('githubCodeBlocks.before', text, options);

  text += '~0';

  text = text.replace(/(?:^|\n)```(.*)\n([\s\S]*?)\n```/g, function (wholeMatch, language, codeblock) {
    var end = (options.omitExtraWLInCodeBlocks) ? '' : '\n';

    // First parse the github code block
    codeblock = showdown.subParser('encodeCode')(codeblock);
    codeblock = showdown.subParser('detab')(codeblock);
    codeblock = codeblock.replace(/^\n+/g, ''); // trim leading newlines
    codeblock = codeblock.replace(/\n+$/g, ''); // trim trailing whitespace

    codeblock = '<pre><code' + (language ? ' class="' + language + ' language-' + language + '"' : '') + '>' + codeblock + end + '</code></pre>';

    codeblock = showdown.subParser('hashBlock')(codeblock, options, globals);

    // Since GHCodeblocks can be false positives, we need to
    // store the primitive text and the parsed text in a global var,
    // and then return a token
    return '\n\n~G' + (globals.ghCodeBlocks.push({text: wholeMatch, codeblock: codeblock}) - 1) + 'G\n\n';
  });

  // attacklab: strip sentinel
  text = text.replace(/~0/, '');

  return globals.converter._dispatch('githubCodeBlocks.after', text, options);
});