New Markdown extension

[markseuffert]

The current Markdown extension is based on Markdown Extra by Michel Fortin. I made an alternative extension based on Parsedown Extra by Emanuil Rusev. It supports strikethrough and task lists, these are additional Markdown features which do not exist in all Markdown implementations.

Example page with additional Markdown features:

---
Title: Markdown test page
Parser: markdown
---
Normal **bold** *italic* ~~strikethrough~~ `code`

Making a task list:

- [x] item one
- [ ] item two
- [ ] item three

Settings for switching Markdown parser:

Parser: markdown = Markdown extension, based on Markdown Extra
Parser: parsedown = Parsedown extension, based on Parsedown Extra

I think performance and features are similar. Parsedown Extra is about 20% smaller than Markdown Extra. Parsedown Extra has some known problems, although all implementations produce slightly different HTML output, there are features which are incorrect or missing. At the moment Parsedown has problems with footnotes, definition lists and special attributes.

Any thoughts?

[schulle4u]

+1 for a change. If I understand right Parsedown even has some kind of extension feature, maybe this can be helpful for Yellow to implement special tags if widely requested by users.
I'm currently testing the plugin on one of my more active Yellow sites, everything works fine as it seems. There is indeed no significant increase of page loading speed, haven't exactly measured it however.

[schulle4u]

Just noticed that Parsedown is not able to parse element attributes, e.g.:

[Mastodon](https://mastodon.social/@schulle4u){rel=me}

This works in the markdown parser, while Parsedown puts the last bracket as normal text after the link. Parsedown Extra apparently only recognizes ID and class attributes, but no special attributes like in the above example.

See also: erusev/parsedown-extra#120

[markseuffert]

Latest release added strikethrough and task list to the default Markdown parser.

Now they have a (more or less) identical feature set.

[markseuffert]

Latest releases added better support for notices, CSS and HTML.

Making notices:

! Here's a notice with warning

!! Here's a notice with error

!!! Here's a notice with tip

Using CSS:

! {.class}
! Here's a notice with custom class.
! Text can span over several lines
! and contain Markdown text formatting.

Using HTML:

<strong>Text with HTML</strong> can be used optionally.
<img src="/media/images/photo.jpg" alt="This is an example image">
<a href="https://datenstrom.se" target="_blank">Open link in new tab</a>.

Please note that content files will be filtered trough a HTML whitelist. This means unsafe elements/attributes will be removed automatically. In case you're curious, all safe elements/attributes are defined in the core in function normaliseData(). It should be assumed that safe elements/attributes will change over time and we will need to add new ones. You can verify browser support with https://caniuse.com. If you find out that something is missing, please send a pull request or report it as a bug.

[terhemis]

Hello,
The problem I have with Markdown Extra (if it is still the one Yellow uses) is that it merges two consecutive blockquotes,

> excerpt 1

> excerpt 2

become the the same thing as

> excerpt 1
>
> excerpt 2

I discover that, here on github, it’s different :

excerpt 1

excerpt 2

is different from

excerpt 1

excerpt 2

As in Mark Text, the (great) markdown editor I (currently) use.

Maybe I’m wrong, but I wasn’t able to test with the other parser mentioned above…

[GiovanniSalmeri]

It seems a common problem (or a common difference in the interpretation of ambiguous specifications):

https://babelmark.github.io/?text=%3E+First+line%0A%0A%3E+Second+line

[terhemis]

I’ve seen that Parsedown is available as an extension, tried it, and it solves this particular problem

[schulle4u]

@terhemis Thanks for reporting. This is a rather historical bug since the markdown extension follows the original MarkdownExtra code in most parts. An updated Markdown extension has just been uploaded which should fix consecutive blockquotes.