How to extend mdast?

[eliyap]

Hi All!

I wanted to implement Pandoc's ==highlight== syntax, and since the existing GFM strikethrough is very similar, I thought I would start there.

However, I noticed that the type annotations rely on a pre-existing "Delete" extension. What is the correct way to extend PhrasingContent to include, say, a new "Mark" type (to correspond to the html tag)?

[wooorm]

Hey!

One part of how to extend mdast is conceptual, and you already found it. Your mark syntax is Phrasing content.
The other part is TypeScript-specific. You can define a new Mark node that extends from Parent, with a type: 'mark', and children: PhrasingContent[], and then register the mark node by adding it to StaticPhrasingContentMap:

https://github.com/DefinitelyTyped/DefinitelyTyped/blob/fe99cda97743cac0940e4960e3a904b655277362/types/mdast/index.d.ts#L76-L101

[shlroland]

When I switched back to the commit before upgrading to the latest TypeScript version, I found that the issue might not be related to TypeScript version inconsistency. The actual problem seems to be that when I upgraded the project's mdast to the latest version 4.0, some remark plugins were still dependent on the older version of mdast, which caused this issue to occur.

[ChristianMurphy]

@shlroland unified, micromark, and most of packages on npm follow semantic versioning https://semver.org/
A major version means it is a breaking change and incompatible with previous versions.
typescript sometimes includes breaking changes in minor versions as well.
The version numbers and change logs are communicated so adopters (like yourself) have the information to choose versions which are compatible across projects.
If you choose incompatible versions, it won't work.

That fact doesn't particularly relate this this thread, which is about extending mdast.
If you have a specific question about extending the mdast types, feel free to ask it.
If you need general micromark support, feel free to start a new thread https://github.com/orgs/micromark/discussions/new?category=q-a
In either case, please review the support guidelines https://github.com/micromark/.github/blob/main/support.md for recommendations on how to ask questions so others can effectively help you.