Footnotes are not supported

[DanielRuf]

Just as information, footnotes are not supported and simply inlined by luasmith:

test-link.md:

---
title: Title of the post
description: Short description of the post (for the Atom feed).
date: 2025-04-22
---

Content goes here. Note you can [^1].

## abc
More content goes here. Note you can [^1].

[^1]: https://example.com

Results in:

While GitHub supports them and creates a footnote area:

There is a feature request in the upstream library that is used in luasmith, that you can find at mity/md4c#106.

[fabsh]

I am currently rebuilding my website with luasmith and I really like it so far. I totally need this feature, though. Not sure I'm a good enough coder to help, certainly in C I'm not, but if there's anything I can do, I would be willing to try!

[DanielRuf]

I briefly searched for "footnote" in the md4c repo and found at least 1 pullrequest that implements something else but according to the todo in the description skips footnotes.

So far I did not yet have the time to take a closer look at the code, but maybe the changes contain some hints, where the implementation for footnotes may be needed.

The PR in question can be found at mity/md4c#175

Some of the forks also seem to contain further changes: https://github.com/mity/md4c/network
Maybe you find something there, that can be merged into the fork at https://github.com/jaredkrinke/md4c

I scrolled many pixels to the right and it looks promising regarding "there might be something":

Let me know if you find a commit / change there, that has something to do with support for footnotes.
I am currently busy with something at work and can check this this evening or in the next days.

[jaredkrinke]

(This was written without looking at any forks that were just noted)

md4c (the Markdown library luasmith is built upon) doesn't have an obvious way to support out-of-order rendering, so unfortunately I don't see a convenient way to support footnotes. Maybe someone has done it, but that would probably be a massive change.

Only options I see are either adding some ugly Lua-to-md4c-back-to-Lua hack or rewriting luasmith to use something more featureful like cmark-gfm -- neither option sounds good to me :)

Edit: other options:

• Find a Lua-based Markdown processor that supports footnotes and reimplement the Markdown plugin with it (this would kill performance, but could be a drop-in replacement for anyone interested)
• Shell out to cmark-gfm (would add a dependency and probably kill performance, but still a drop-in solution)
• Preprocess the Markdown using e.g. LPEG to rewrite footnotes into something that md4c could handle unmodified (a fragile hack, but probably much easier than messing with md4c's internals)

I guess there are actually a lot of options. None are great, of course.

[jaredkrinke]

We should definitely document which Markdown features are supported in README.md.

[DanielRuf]

I've checked the forks from the linked network graph and also all the forms from the full list for the last 2 years + a few more.
None of them implement footnotes.

So what are possible solutions for users, who may need this?
You mentioned possible dropin solutions, would this be generally possible and could this be documented?

Maybe this could be part of #51, where possible alternative solutions can be linked in the README if a specific featureset is needed.

As alternative solution I'm looking also into additional preprocessing / postprocessing as part of the pipeline via some sort plugins, but do not yet have a working solution.

[jaredkrinke]

I looked briefly into Lua-based Markdown processors and it looks like Lunamark supports footnotes. I'm not sure if it supports tables. There might need to be a post-processing step to ensure relative Markdown links still work as in luasmith's implementation.

Shelling out to cmark-gfm (via io.popen in the Lua stdlib) would probably work too, but spinning up a new process for each item would probably be pretty slow. Post-processing would certainly be needed with this option as well.

Note that these would be site-specific workarounds and not something I'd want to integrate into luasmith itself. I also don't have immediate plans to attempt either of these. If there was enough interest and I had a chunk of free time, it would be doable, but this project hasn't exactly set the SSG world on fire ;)

[DanielRuf]

See also #42 (comment) - if this works and they want to contribute, that would be a great simple solution.

Still I had not yet much time after work, so still at the early beginning of my Lua journey.
But I'm open even for such a simple solution instead of yet another embedded library, which for me perfectly fits with the philosophy of this project (being small and efficient).

[jaredkrinke]

If I'm reading that change correctly, that does a global substitution, so even footnote patterns inside code blocks would get erroneously processed. Might be ok to document as a "your mileage may vary" approach, but I wouldn't want to give people the wrong impression that it is supported or robust.

Anyway, seems helpful! Just need to find the right place to document hacks like that.

[fabsh]

Ooooh. I had no idea something like this was possible inside theme.lua! That's a great idea. And it should be possible to pair it with a function that detects if you are inside code or pre blocks and disables it accordingly. I will experiment with this and report back.

[alunya-cat]

If I'm reading that change correctly, that does a global substitution, so even footnote patterns inside code blocks would get erroneously processed. Might be ok to document as a "your mileage may vary" approach, but I wouldn't want to give people the wrong impression that it is supported or robust.

Anyway, seems helpful! Just need to find the right place to document hacks like that.

I hadn't realized that... It happens to [^X] and [TOC] (check out https://alunya.cat/alan/_test.html).

However, I still don't want to share it completely because, as you can see, there are many errors to correct. My intention is to create a repository specifically for the theme, explain the changes I've made so that everyone can choose what to add to their own theme, and finally make a PR adding the theme to the list of themes as you told me in #37 (comment).

[jaredkrinke]

However, I still don't want to share it completely because, as you can see, there are many errors to correct. My intention is to create a repository specifically for the theme, explain the changes I've made so that everyone can choose what to add to their own theme, and finally make a PR adding the theme to the list of themes as you told me in #37 (comment).

Ha, you are correct! There was already a plan for sharing/linking other themes--I just forgot about it!

Sounds great, thank you!

[DanielRuf]

md4c has seen some big changes this year and it seems footnote support was added: mity/md4c#106