Support footnote links

• Markwon version: 4.6.2

Hey @noties. It’s more of a feature request. Can markwon support footnotes or maybe how can i implement footnote links ?

Here's a simple footnote,[^1] and here's a longer one.[^bignote]

[^1]: This is the first footnote.

[^bignote]: Here's one with multiple paragraphs and code.

In the above example, clicking on [^1], scrolls to to bottom [^1]: This is the first footnote.

[noties]

Hello @damionx7 ,

the [comment]: comment markdown is actually a link reference, for example:

<!-- the [link] would become [link](https://example.com) -->
This is a [link]

[link]: https://example.com

And footnotes indeed are clashing with those. Unfortunately the link references are hardcoded into the parser, so it is not easy to add support for footnotes with current syntax

[noties]

Hello @damionx7 ,

yeah, sorry, I was unavailable. I don’t think it is possible to override default handling of reference links within the parser itself. There are just too many parts to consider. If you are interested you can take a look at the LinkReferenceDefinitionParser in the commonmark-java project. And related ParagraphParser and DocumentParser parsers. Adding footnotes support would require a major change to all these components.

I guess this is where commonmark-java inflexibility starts to play a role. Markwon has been relying on commonmark internals in order to tweak its parsing and make it more flexible. But lately they had changed internals in order to add support for source positions (unfortunately they are not suitable for editors, so good for nothing really). And this left Markwon behind as change is a bit more that I had anticipated before. Right now I’m seriously consider moving to other parsing stack, but still not sure if an abstract parsing layer should be added (so backends could be changed) or a different engine should be solely used or, finally, writing own solution for parsing.

Anyway, right now I see conceptually only one solution to the footnotes. Preprocess raw markdown and do no rely on parser at all. For example it is no uncommon for footnotes to be styled (marked) so you would want to run Markwon other then also. Something along these lines (pseudocode):

// matcher to match `[^1]` links to actual footnote contents
val matcher = referencesMatcher(markdown)
while (matcher.find() {
  val content = findContent(matcher, markdown)
  // content is found `[^1]: My contents`
  if (content != null) {
    // replace link `[^1]` so parser do not handle it
    replaceFootnoteLink()
    // footnote contents can be markdown itself, so parse it
    val footnote = markwon.toMarkdown(content)
    addFootnote(footnote)
  }
}

1. find all footnote links in text [^1]
2. check if those have footnote content [^1]: **Footnote** content
3. exclude those from being parsed (but still be referenced after parsing, important thing to decide on)
4. find a way to display footnote and handle clicks on it (or other way of handling them altogether)