Is it possible to add parser information to a file's front matter data?

[pspeter3]

Eg is it possible to add a toc or links property to the front matter data based on the parser? This could be achieved by parsing the content in eleventyComputed but that seems comparatively wasteful.

[Ryuno-Ki]

Hm, couldn't you use a transform for that?
Why do you need the information in the front-matter?

[pspeter3]

Oh are you proposing that for each file, I make a collection which is the files that link to it?

[Ryuno-Ki]

I'm not quite sure to got you either 😅

Another alternative to my solution could be just to make a data file which just globs and parses all the markdown there.

For globbing, there are already options. For example, collections. You could look into whether those get close to what you want before reinventing the wheel.

I just want to be able to use the parser hooks to create an array of links.

Links to what?

My understanding right now is, that you have a blog post. That is part of a multi-part article series about a certain topic. Perhaps even a longread. So there shall be a ToC at the beginning to prepare the reader about the content below. At the bottom, you want to link to other articles in that series.

Those article-series could share a tag for example, which would allow the creation of a collection.
The collection could be paginated to generate the prev- and next links.

But perhaps I got the use case wrong. What is this Eleventy Garden?

[pspeter3]

Eleventy Garden is an example of someone trying to implement Roam In Eleventy. Imagine that you have the following files:

alpha.md

---
name: Alpha
---
The beginning of the site.

beta.md

---
name: Beta
---
The second page in the site. Comes after [Alpha](/alpha/)

omega.md

---
name: Omega
---
The last page in the site. Comes after [Alpha](/alpha/) and [Beta](/beta/)

I would want the following front matters:

[
  { "permalink": "/alpha/", "links": [], /* ... */ }
  { "permalink": "/beta/", "links": ["/alpha/"], /* ... */ }
  { "permalink": "/alpha/", "links": ["/alpha/", "/beta/"], /* ... */ }
]

That way I can show that Beta and Omega link to alpha on the alpha page. I'm trying to build backlinks via the link property.

[Ryuno-Ki]

How is the parser supposed to know the order in your opinion?

[pspeter3]

It's not supposed to know the order. I just want the parser to expose that Omega links to Alpha & Beta.

[zachleat]

Interesting—are there any hooks you can use via a markdown-it plugin? See https://www.11ty.dev/docs/languages/markdown/#optional-set-your-own-library-instance

[pspeter3]

You would need to add a custom rule that basically produces a side effect. Essentially the equivalent of creating a linter or transform in Eleventy. The API is certainly easier in marked which has events for each node but you could make it work with markdown-it as well. Creating an API to connect the rule to the Eleventy data is the hard question.

[pspeter3]

For example you could use the callback on the markdown-it-anchor to build the TOC if you wanted to https://github.com/valeriangalliat/markdown-it-anchor

[kkgthb]

I think I just found a workaround, if I'm understanding this correctly, @pspeter3. I just added both a pages.11tydata.js and a pages.11tydata.json file to a pages folder. The JavaScript took care of things w/ complex variables, like stripping pages out of permalink even if permalink was set in the .md file's front matter. The only thing it wouldn't let me set was tags. So I did {"tags": "pages"} in the JSON and they work together like a charm as of late January, 2021.