Expose sections as documents (VDOM)

[kptdobe]

During the hackathon, I "played" with sections and the first thing I always do is transforming the sections into documents (VDOM) where the API is must front-end developer oriented than MDAST... See https://github.com/kptdobe/helix-sections-playground/blob/master/src/html.pre.js#L37-L38.

Manipulation, inserting nodes... everything is more simple and in the pre.js, I think a developer would rather care about the DOM than the data structure when consuming sections.

I propose that the pipeline takes care of the transformation.

@trieloff WDYT ?

[kptdobe]

Well... +/- the types!
Maybe the sections should be an object like:
{
"index": "index of the section in the list",
"types": ["list of computed types"],
"document": {VDOM document object}
}

[trieloff]

I think just adding a document node to each section would do no harm and still grant full access to the MDAST.

[kptdobe]

With #279, <sections> tags will be added to the content.document object (and <hr> removed). This will give a VDOM API access on the sections. 2 options now:

1. we do not need this enhancement
2. the idea of a document property on each section could be recycled into a reference to the section node inside the content.document

[trieloff]

we do not need this enhancement

And in addition, I think we will at some point deprecate content.sections.

[kptdobe]

Then we need to think where do we put the mast, index and types properties. Maybe as data in the VDOM object ?

[trieloff]

Good point & good idea.

[ramboz]

This has now been tackled in #379 and is in v4.0.0
@kptdobe, @trieloff Would it be safe to close the issue? or do you still see remaining points that aren't covered