Add TODO list support for Blackfriday

[bep]

Fixes #2269

• Basic support
• A flag to turn it off
• Add a way to style the list bullet away
• A test
• Some documentation

[bep]

But we need to add a CSS-class somewhere so it is possible to hide the list bullet (as GitHub does).

/cc @phtan

[bep]

This is how GitHub does it for the li-item:

class="task-list-item enabled"

[bep]

I have rebased this against master now and I suspect the tests will pass.

I'm planning to implement this for the MMark renderer, too, but I kind of need this code to do that.

@digitalcraftsman @moorereason I know this works, but do you have any complaints? Good to merge?

[moorereason]

Any reason why you set checked and disabled to empty strings? I would use:

<input type="checkbox" checked disabled class="task-list-item">

[bep]

Any reason why you set checked and disabled to empty strings?

If you followed the looooong discussion in the related issue you will see that the core part of the implementation is borrowed from @shurcooL ... Knowing that he writes compilers for fun (gopherjs), I'm pretty sure he is correct. And reading the spec (https://www.w3.org/TR/html-markup/syntax.html#syntax-attributes), I don't see any "attribute without value" option. It probably works in most (all?) browsers, but isn't entirely correct.

[moorereason]

Have another look: https://www.w3.org/TR/html-markup/syntax.html#syntax-attr-empty

[dmitshur]

If you followed the looooong discussion in the related issue you will see that the core part of the implementation is borrowed from @shurcooL ... Knowing that he writes compilers for fun (gopherjs), I'm pretty sure he is correct.

Thanks, but I would recommend reviewing that code from scratch. I wrote it a while ago and decisions/research done back then may not apply or still be valid today. It also highly depends on the context where it's used (version of HTML, etc.).

Any reason why you set checked and disabled to empty strings?

There was no good reason, it was just one of many ways of doing it. I think your suggestion is valid and makes sense. But I haven't looked at the specifics of HTML/XHTML versions hugo uses, its browser support, etc.

[bep]

Both variants is fine, then. I chose the one with the least amount of work.

[bep]

@moorereason I have simplified the HTML attributes re. your comment, does it then look generally OK?

@shurcooL if people use your GitHub renderer (or whatever it is named), you should take another look at your TODO-list implementation. A HTML list without any CSS classes isn't very easy to style.

[digitalcraftsman]

The commit looks fine. I agree with @moorereason that the empty strings can be removed because the w3c spec handles them equivalent:

Note that empty attribute syntax is exactly equivalent to specifying the empty string as the value for the attribute, as in the following example.

<input disabled="">

[dmitshur]

@shurcooL if people use your GitHub renderer (or whatever it is named), you should take another look at your TODO-list implementation. A HTML list without any CSS classes isn't very easy to style.

The goal of the github_flavored_markdown package is to render GitHub Flavored Markdown, generating HTML and providing the CSS that displays it. The user isn't meant to customize it in any way – that's what blackfriday and its custom renderers and options are for. If you think there's a bug, you should open an issue in that repo.

[bep]

If you think there's a bug, you should open an issue in that repo.

I don't use that repo, just giving you a heads up.

[github-actions]

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