Kramdown GFM Parser extension for [[wikilinks]]

kramdown_gfm_wikilink.rb

require 'kramdown/parser/kramdown'
require 'kramdown-parser-gfm'

# Based on the API doc comment: https://github.com/gettalong/kramdown/blob/master/lib/kramdown/parser/kramdown.rb
class Kramdown::Parser::GFMWikiLink < Kramdown::Parser::GFM
  def initialize(source, options)
    super

    # Override existing Table parser to use our own start Regex which adds a check for wikilinks
    @@parsers.delete(:table) #Data(:table, TABLE_START, nil, "parse_table")
    self.class.define_parser(:table, TABLE_START)

    @span_parsers.unshift(:wikilinks)
  end

  # Override Kramdown table pipe check so we can write `[[pagename|Anchor Text]]`.
  # https://github.com/gettalong/kramdown/blob/master/lib/kramdown/parser/kramdown/table.rb
  # Regex test suite: https://regexr.com/5rb9q
  TABLE_PIPE_CHECK = /^(?:\|(?!\[\[)|[^\[]*?(?!\[\[)[^\[]*?\||.*?(?:\[\[[^\]]+\]\]).*?\|)/.freeze  # Fail for wikilinks in same line
  TABLE_LINE = /#{TABLE_PIPE_CHECK}.*?\n/.freeze  # Unchanged
  TABLE_START = /^#{OPT_SPACE}(?=\S)#{TABLE_LINE}/.freeze  # Unchanged

  WIKILINKS_MATCH = /\[\[(.*?)\]\]/.freeze
  define_parser(:wikilinks, WIKILINKS_MATCH, '\[\[')

  def parse_wikilinks
    line_number = @src.current_line_number

    # Advance parser position
    @src.pos += @src.matched_size

    wikilink = Wikilink.parse(@src[1])
    el = Element.new(:a, nil, {'href' => wikilink.url, 'title' => wikilink.title}, location: line_number)
    add_text(wikilink.title, el)
    @tree.children << el

    el
  end

  # [[page_name|Optional title]]
  # For a converter that uses the available pages, see: <https://github.com/metala/jekyll-wikilinks-plugin/blob/master/wikilinks.rb>
  class Wikilink
    def self.parse(text)
      name, title = text.split('|', 2)
      title = name if title.nil?
      self.new(name, title)
    end

    attr_accessor :name, :title
    attr_reader :match

    def initialize(name, title)
      @name = name.strip.gsub(/ +/, '-')
      @title = title
    end

    def title
      @title || @name
    end

    def url
      "/wiki/#{@name.downcase}"
    end
  end
end

I'm using this in a nanoc statically built website.

  filter :kramdown, KRAMDOWN_OPTS.merge({input: 'GFMWikiLink'})

That option to select the flavor GFMWikiLink is all I needed to do.

Didn't actually write anything on the wiki since figuring this out, but it's at https://christiantietze.de/wiki/ :)

The website repo isn't public so I don't have to worry if I ever committed a password -- but if you want to see anything, send me an email.

Thanks! Question -- do you really need to redefine the Table regexes? Is there not a way to force the wikilinks regex match to happen first?

@rathboma I think no; but I'd be happy if you find a better way :) The table parser is block-level, the wikilink parser span level. You'd need to add a block level parser that detect a non-table block with wikilink inside and then prevent the table, maybe 🤔

Fair enough! FYI I got this working. It's great. thank you for posting!