Allow for fragmented list from a directive

[thejcannon]

👋

Howdy! Trying out Marp and I'm liking it so far.

One issue I've run into is that Prettier pretty unambiguously formats unordered lists using a hyphen -, which means it doesn't play nicely with Marp's fragmented list.

Here's some relevant issues:

• Markdown Unordered List Item Symbol  prettier/prettier#4251
• Prettier uses asterisks (*) in list when list using dashes (-) is preceded or followed by list using asterisks prettier/prettier#11304 (mentions marp! 🎉 )

Support for a directive would solve the corss-roads of Prettier and Marp, and as mentioned in the second link, would be very explicit.

Thanks!

[thejcannon]

I should add, the current workaround is:

<!-- prettier-ignore -->
* one
* two
* three

[yhatt]

Thank you for reminding me. As you said, a configurable fragmented list was there on the far of the roadmap.

NOTE: The defined markups may be an opinionated. I want to start with a dogmatic parser for aiming to less-configuration, but it may change the target character, or make the markup configurable by global directives.

— #148

One of the ideas I had been thought at that time is to specify a marker symbol via the global/local directive. The Markdown author can control a marker for the fragmented list as like that:

<!-- fragmentMarker: "-" -->

- Step 1
- Step 2
- Step 3

---

<!-- fragmentMarker: ["-", "*"] -->

- Step 1
  - Step 1-1
  - Step 1-2
* Step 2
  * Step 2-1
  * Step 2-2

This idea is using Marp's existing directive syntax.

And the member of Prettier @kachkaev provides another interesting idea:

My suggestion would be to reach out to Marpit folks and suggest some alternative syntax for fragmented lists. For example, this can be - <!-- click --> list item, which is explicit about what it does. This will surface the knowledge, so make Marpit markdowns less cryptic for folks who haven’t read the docs.

— prettier/prettier#11304 (comment)

- <!-- fragmented --> Step 1
- <!-- fragmented --> Step 2
- <!-- fragmented --> Step 3

(Marpit framework does not limit how to proceed the fragmented list so I use more inclusive word fragmented instead of click)

Pros: Explicit and never break any existing CommonMark rules. Annotating the list item with HTML comment is similar approach to Marp Core's fitting header <!-- fit --> so many Marp(it) users may be easy to know.

Cons: Looks like a bit redundant. The marker * will no longer work as the fragmented list so it may break compatibillity with hundreds of existing Marp Markdowns..

[thejcannon]

Correct me if I'm wrong, but couldn't you support both:

• * means fragmented list
• - <!-- fragmented --> ... ALSO means fragmented list

Then you won't break compatibility and Prettier is still happy.

---

I honestly don't have a strong opinion. The tool already does a good job so I'm inclined to just go along with whatever works 😄 👍

[codingluke]

I can only support @thejcannon's proposal. I just started to use fragmented lists together with prettier and landed here ;)

The comment per item is more flexible so I would prefere it over the fragmentMarker proposal. even though this would be in 99% more convenient. Best would be to support all 😅