Support MultiMarkdown footnotes

[mariussoutier]

Hi Jens,

I know it's not part of the official spec, but writing without footnotes seems kind of strange. Maybe you could implement the footnotes that are available in MultiMarkDown:

https://github.com/fletcher/MultiMarkdown/wiki/MultiMarkdown-Syntax-Guide#footnotes

Currently they are interpreted as links and and result in an error:

unresolved link reference: ^my-footnote

Cheers
Marius

[jenshalm]

Yes, the current version supports the Markdown features as documented in the "Supported Markup" chapter in the Laika manual. For Markdown this means the original syntax description (which is not very feature-rich) plus the few features Laika adds for all markup languages, like directives.

The full MultiMarkdown feature set is already on the road map:

http://planet42.github.io/Laika/index.html#road-map

But this is for version 0.9 and I currently work on 0.6, so it won't happen in the coming months. I had the focus on the parser side for quite some time, therefore first want to fill the gaps in output formats now (mainly PDF and epub).

[mariussoutier]

Ok, I see. Looking forward to it!

[valencik]

As on Laika 1.3.2, footnotes are not support from markdown syntax, even with Markdown.GithubFlavour enabled.

//> using scala 3.3.7
//> using dep org.typelevel::laika-core:1.3.2

import laika.api._
import laika.format._

@main def run(): Unit =
  val markdown = """
    |# Footnotes
    |
    |Laika's internal model supports footnotes[^1].
    |However, its syntax parsing support is limited.
    |
    |[^1]: The Laika Document AST has a Footnote node.
    |""".stripMargin

  val transformer = Transformer
    .from(Markdown)
    .to(HTML)
    .using(Markdown.GitHubFlavor)
    .build

  transformer.transform(markdown) match
    case Right(html) =>
      println(html)
    case Left(error) =>
      println(s"Error: $error")

Prints (minus my artisanal formatting):

Error: InvalidElements(Chain(
 InvalidSpan(
  RuntimeMessage(error,unresolved link id reference: ^1,Options(None,Set())),
   LineSource(/: offset 0 - length 4 - root offset 55),
   Literal([^1],Options(None,Set())),
   Options(None,Set())
  ),
 InvalidSpan(
  RuntimeMessage(error,unresolved link id reference: ^1,Options(None,Set())),
  LineSource(/: offset 0 - length 4 - root offset 110),
  Literal([^1],Options(None,Set())),
  Options(None,Set()))
))

Reopening this issue as this was recently requested in Typelevel Discord and I think it would be a nice addition.

Note however, that footnotes are not specified in the latest CommonMark spec

Presumably GitHub markdown supports footnotes in markdown though¹.
So this would have to be an extension to Markdown.GithubFlavour, which I imagine most people are using anyways.

Footnotes

1. Yes, it does. ↩