Enable task lists in GFM

[oschihin]

This is a feature request.

Specification

According to the plugin specs, this (wonderful, great, irreplacable) plugin supports three MD-flavors, with it, Github Flavored Markdown. I have configured it accordingly: Markdown flavor: github flavored.

One very useful extension from GFM are task lists [1], but they do not seem to work in this plugin. I write:

<markdown>
Shopping List

- [ ] Salt
- [x] Pepper
- [ ] Vinegar
- [ ] Vine

</markdown>

List items display like

<div class="li">[ ] Salt</div>

and not with <input type="checkbox">

Motivations

The motivation is

1. Accordance with the standard (GMF)
2. Dokuwiki can be used for checklists / task lists, very handy in a lot of process cases

[1] (https://github.github.com/gfm/#task-list-items-extension-)

[mizunashi-mana]

This plugin uses https://github.com/cebe/markdown, and the spec is followed it.
Now, the library doesn't provide some support for task lists: cebe/markdown#29 .

I marked this issue as an upstream issue.
If the library will support task list, this plugin will support it.

Now, I recommend to use https://www.dokuwiki.org/plugin:todo outside markdown block.

[doekenorg]

FYI: We also needed this, so we built a trait for it you can easily use.

https://github.com/kirra/markdown-task-lists.

[mizunashi-mana]

I push a branch supporting tasklist using kirra/markdown-task-lists . However, this library supports only PHP >= 7.1 though DokuWiki is used on older PHP.

This plugin support older PHP users, so I decide not to merge tasklist support now.